In-plane Magnetic Field Dependent Magnetoresistance of Gated Asymmetric Double Quantum Well

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磁共振新技术评估阿尔茨海默病脑内铁沉积

磁共振新技术评估阿尔茨海默病脑内铁沉积李思瑶;何慧瑾【摘要】越来越多的研究证明阿尔茨海默病(AD)有脑内铁的代谢紊乱、脑铁沉积增加,且脑内铁的过量沉积与氧化应激及β淀粉样变密切相关,与AD的发生和病情的进展关系密切.MRI可以无创性地检查脑内铁的变化,因而对AD的发病机制、早期诊断及动态监测病情变化具有重要价值.就目前所采用的AD脑铁测量的各种MRI序列及其优缺点进行综述,并介绍尚未应用于AD的定量测量脑铁的新技术.【期刊名称】《国际医学放射学杂志》【年(卷),期】2010(033)001【总页数】4页(P6-9)【关键词】阿尔茨海默病;脑内铁沉积;磁共振成像;脑铁测量【作者】李思瑶;何慧瑾【作者单位】200040上海,复旦大学附属华山医院放射科;200040上海,复旦大学附属华山医院放射科【正文语种】中文越来越多的研究证明铁及其他一些金属离子（铜、锌等）与阿尔茨海默病（Alzheimer's disease,AD）的发病密切相关。

具有氧化还原活性的铁离子可与过氧化氢反应产生羟自由基从而引起氧化应激反应。

对尸检脑组织的生化分析显示AD病人脑内总铁浓度升高，但是皮质铁蛋白的浓度降低（皮质内的铁大部分是以无活性铁蛋白的形式存在）[1]。

细胞外的淀粉样斑块及细胞内的神经纤维缠结（NFT）是AD的标志性病理改变，且这一改变与铁密切相关[2]。

铁为顺磁性物质，可以降低质子弛豫率，在T2WI、T2*WI及磁敏感加权成像(susceptibility weighted imaging,SWI)上呈低信号，淀粉样斑块有内源性铁的沉积[3]，在MRI 上产生对比，从而可对AD进行评价。

1 横向弛豫时间（T2、T2*）及横向弛豫率（R2、R2*）T2、T2*加权成像的对比主要来源于组织各组成成分磁敏感性不同，如铁、去氧血红蛋白、髓鞘及组织的微观结构及其含水量等均可造成组织的磁敏感性差异[4]。

铁为顺磁性物质，可以缩短 T2、T2*，影响组织的R1、R2*。

磁学径向克尔英文 kerr effect

IntroductionThe Kerr effect, also known as the magneto-optic Kerr effect (MOKE), is a phenomenon that manifests the interaction between light and magnetic fields in a material. It is named after its discoverer, John Kerr, who observed this effect in 1877. The radial Kerr effect, specifically, refers to the variation in polarization state of light upon reflection from a magnetized surface, where the change occurs radially with respect to the magnetization direction. This unique aspect of the Kerr effect has significant implications in various scientific disciplines, including condensed matter physics, materials science, and optoelectronics. This paper presents a comprehensive, multifaceted analysis of the radial Kerr effect, delving into its underlying principles, experimental techniques, applications, and ongoing research directions.I. Theoretical Foundations of the Radial Kerr EffectA. Basic PrinciplesThe radial Kerr effect arises due to the anisotropic nature of the refractive index of a ferromagnetic or ferrimagnetic material when subjected to an external magnetic field. When linearly polarized light impinges on such a magnetized surface, the reflected beam experiences a change in its polarization state, which is characterized by a rotation of the plane of polarization and/or a change in ellipticity. This alteration is radially dependent on the orientation of the magnetization vector relative to the incident light's plane of incidence. The radial Kerr effect is fundamentally governed by the Faraday-Kerr law, which describes the relationship between the change in polarization angle (ΔθK) and the applied magnetic field (H):ΔθK = nHKVwhere n is the sample's refractive index, H is the magnetic field strength, K is the Kerr constant, and V is the Verdet constant, which depends on the wavelength of the incident light and the magnetic properties of the material.B. Microscopic MechanismsAt the microscopic level, the radial Kerr effect can be attributed to twoprimary mechanisms: the spin-orbit interaction and the exchange interaction. The spin-orbit interaction arises from the coupling between the electron's spin and its orbital motion in the presence of an electric field gradient, leading to a magnetic-field-dependent modification of the electron density distribution and, consequently, the refractive index. The exchange interaction, on the other hand, influences the Kerr effect through its role in determining the magnetic structure and the alignment of magnetic moments within the material.C. Material DependenceThe magnitude and sign of the radial Kerr effect are highly dependent on the magnetic and optical properties of the material under investigation. Ferromagnetic and ferrimagnetic materials generally exhibit larger Kerr rotations due to their strong net magnetization. Additionally, the effect is sensitive to factors such as crystal structure, chemical composition, and doping levels, making it a valuable tool for studying the magnetic and electronic structure of complex materials.II. Experimental Techniques for Measuring the Radial Kerr EffectA. MOKE SetupA typical MOKE setup consists of a light source, polarizers, a magnetized sample, and a detector. In the case of radial Kerr measurements, the sample is usually magnetized along a radial direction, and the incident light is either p-polarized (electric field parallel to the plane of incidence) or s-polarized (electric field perpendicular to the plane of incidence). By monitoring the change in the polarization state of the reflected light as a function of the applied magnetic field, the radial Kerr effect can be quantified.B. Advanced MOKE TechniquesSeveral advanced MOKE techniques have been developed to enhance the sensitivity and specificity of radial Kerr effect measurements. These include polar MOKE, longitudinal MOKE, and polarizing neutron reflectometry, each tailored to probe different aspects of the magnetic structure and dynamics. Moreover, time-resolved MOKE setups enable the study of ultrafast magneticphenomena, such as spin dynamics and all-optical switching, by employing pulsed laser sources and high-speed detection systems.III. Applications of the Radial Kerr EffectA. Magnetic Domain Imaging and CharacterizationThe radial Kerr effect plays a crucial role in visualizing and analyzing magnetic domains in ferromagnetic and ferrimagnetic materials. By raster-scanning a focused laser beam over the sample surface while monitoring the Kerr signal, high-resolution maps of domain patterns, domain wall structures, and magnetic domain evolution can be obtained. This information is vital for understanding the fundamental mechanisms governing magnetic behavior and optimizing the performance of magnetic devices.B. Magnetometry and SensingDue to its sensitivity to both the magnitude and direction of the magnetic field, the radial Kerr effect finds applications in magnetometry and sensing technologies. MOKE-based sensors offer high spatial resolution, non-destructive testing capabilities, and compatibility with various sample geometries, making them suitable for applications ranging from magnetic storage media characterization to biomedical imaging.C. Spintronics and MagnonicsThe radial Kerr effect is instrumental in investigating spintronic and magnonic phenomena, where the manipulation and control of spin degrees of freedom in solids are exploited for novel device concepts. For instance, it can be used to study spin-wave propagation, spin-transfer torque effects, and all-optical magnetic switching, which are key elements in the development of spintronic memory, logic devices, and magnonic circuits.IV. Current Research Directions and Future PerspectivesA. Advanced Materials and NanostructuresOngoing research in the field focuses on exploring the radial Kerr effect in novel magnetic materials, such as multiferroics, topological magnets, and magnetic thin films and nanostructures. These studies aim to uncover newmagnetooptical phenomena, understand the interplay between magnetic, electric, and structural order parameters, and develop materials with tailored Kerr responses for next-generation optoelectronic and spintronic applications.B. Ultrafast Magnetism and Spin DynamicsThe advent of femtosecond laser technology has enabled researchers to investigate the radial Kerr effect on ultrafast timescales, revealing fascinating insights into the fundamental processes governing magnetic relaxation, spin precession, and all-optical manipulation of magnetic order. Future work in this area promises to deepen our understanding of ultrafast magnetism and pave the way for the development of ultrafast magnetic switches and memories.C. Quantum Information ProcessingRecent studies have demonstrated the potential of the radial Kerr effect in quantum information processing applications. For example, the manipulation of single spins in solid-state systems using the radial Kerr effect could lead to the realization of scalable, robust quantum bits (qubits) and quantum communication protocols. Further exploration in this direction may open up new avenues for quantum computing and cryptography.ConclusionThe radial Kerr effect, a manifestation of the intricate interplay between light and magnetism, offers a powerful and versatile platform for probing the magnetic properties and dynamics of materials. Its profound impact on various scientific disciplines, coupled with ongoing advancements in experimental techniques and materials engineering, underscores the continued importance of this phenomenon in shaping our understanding of magnetism and driving technological innovations in optoelectronics, spintronics, and quantum information processing. As research in these fields progresses, the radial Kerr effect will undoubtedly continue to serve as a cornerstone for unraveling the mysteries of magnetic materials and harnessing their potential for transformative technologies.。

4.Magnetic field

cos 1 )
More about this model •For an ideal solenoid, whose length is very long, L>>R
2 0, 1 , B LR 0nI
•At the end at point A1 of the solenoid:
2 0,
Consider a circular loop of wire of radius R located in the yz plane and carrying a steady current I. Calculate the magnetic field at an axial point P a distance x from the center of the loop.
Solution:
dB 0Idl rˆ
4πr 2 B 0I (at x 0)
2R
More about this model
a. Magnetic moment
ISnˆ
I R2
Bx
20IBiblioteka 2x2 R23 2
0I R2 2 x2 R2
3 2
2
0
x2 R2
3 2
Chapter 4 Magnetic Field
§1 Magnetism §2 Biot-Savart- Laplace Law §3 Gauss’ Law in magnetism §4 Ampère’s Law §5 Magnetic Force on An Electric Current §6 Magnetic Force on a Moving Charge
d r 2dI r3dr
rq

Linear in-plane magnetoconductance and spin susceptibility of a 2D electron gas on a vicina

a r X i v :c o n d -m a t /0301565v 2 [c o n d -m a t .m e s -h a l l ] 23 S e p 2003Linear in-plane magnetoconductance and spin susceptibility of a 2D electron gas on avicinal silicon surfaceY.Y.Proskuryakov 1,∗,Z.D.Kvon 2,A.K.Savchenko 11School of Physics,University of Exeter,Stocker Road,Exeter,EX44QL,U.K.2Institute of Semiconductor Physics,Novosibirsk,630090,RussiaIn this work we have studied the parallel magnetoresistance of a 2DEG near a vicinal silicon surface.An unusual,linear magnetoconductance is observed in the ﬁelds up to B =15T,which we explain by the eﬀect of spin polarization on impurity scattering.This linear magnetoresistance shows strong anomalies near the boundaries of the minigap in the electron spectrum of the vicinal system.Over the last few years a number of reports have ap-peared on observations of anomalous positive magnetore-sistance (negative magnetoconductance,MC)in high-mobility 2D electron and hole gases in the ﬁeld paral-lel to the 2D plane 1.Such interest is fuelled by the fact that this negative MC is directly related to other unusual properties of high-mobility systems,such as ‘metallic’be-haviour and the transition from ‘metal’to ‘insulator’1.However,until now all studies of in-plane MC were de-voted to the range of low electron densities,N s ,near the ‘metal-insulator’transition.In the case of a 2D elec-tron gas (2DEG)in Si-MOSFET structures the densities studied were below 1012cm −2.The focus of our study is the in-plane MC in a vicinal Si-MOSFET at high electron densities ,N s >1012cm −2.It is well known 2,3,4,5that this system has a superlattice potential on the Si surface,which results in a minigap in the energy spectrum.Previously,the study of the slow electron diﬀraction by atomically pure vicinal Si surfaces cut at small angles θto (100)plane (as shown in Fig.1a)revealed ordered steps,which do not disappear even when specimens are heated up to 1100o C,even in the presence of hydrogen or oxygen 6.The size of these steps was in agreement with theoretical predictions for perfect high-index surfaces 4.This periodic structure is considered to be the reason for the appearance of the superlattice potential 3,4.The minigap in the energy spectrum has an inter-valley character 4,which implies a strong inter-valley interac-tion when the electron energy approaches the minigap.This also leads to the appearance of a logarithmic diver-gence in the density of states D (E )at energies close to the lower edge of the minigap,Fig.1(b).D (E )diﬀers from zero within the minigap because the superlattice is one-dimensional and does not produce a full gap in the spectrum.The discontinuity in D (E )also appears at the upper edge of the minigap.When the smearing Γis less than the width of the minigap ∆,transport coeﬃ-cients exhibit singularities as the Fermi energy E F passes through the boundaries of the minigap 3,4,7.Such systems with a minigap are of interest because they can realise two diﬀerent situations:with an isotropic Fermi surface (FS),and an anisotropic one,dependent on the position of the Fermi level.These two cases corre-spond to diﬀerent ranges of electron densities,where the properties of the 2DEG signiﬁcantly diﬀer:N s <N ′∆(isotropic FS)and N s >N ′∆(anisotropic FS),where N ′∆=π(0.15/L )2is the density corresponding to the on-set of the superlattice minigap.(Here L =a/(2sin(θ))is the superlattice period,θis the angle between the vicinal and (100)silicon surface,a =5.43˚A is the lattice con-stant of Si.)The properties of the 2DEG in the ﬁrst range are identical to those of an ordinary (100)Si-MOSFET,while in the second range the properties of the 2DEG become strongly modiﬁed 3,4.We experimentally investigate the MC in both ranges of N s .A linear magnetoconductance is observed in mag-netic ﬁeld parallel to the plane of the 2DEG,in a surpris-ingly large range of ﬁelds up to 15T.To our knowledge,this is the ﬁrst observation of such an eﬀect.We de-scribe the linear decrease of the conductance with B ||in terms of the screening model 8,where impurity scat-tering gets changed when the 2DEG is spin-polarised by parallel magnetic ﬁeld.The performed analysis suggests that the slope of the linear MC in the ﬁrst range of N s (isotropic Fermi surface)is in agreement with theoretical expectation for the scattering dominated by impurity po-tential.In the second range of N s a signiﬁcant decrease of the magnitude of the MC is observed at the bound-aries of the minigap.This can be attributed to either the modiﬁcation of the transport properties of the electrons near the points of topological transitions of the Fermi surface 7,11,or suppression of the spin susceptibility.The studied samples are Hall-bar Si-MOSFETs fabri-cated on a vicinal Si(17,2,2)surface,tilted from (100)by an angle θ=9◦40’around the direction [011].The su-perperiod in this case is L =16.2˚A ,which corresponds to N ′∆≃2.6×1012cm −2.As this surface is just slightly dif-ferent from the (811)surface at θ=10o ,one can expect qualitatively the same dispersion relation and other prop-erties as those for Si(n11)described in detail in Ref.4.We study the behaviour of the 2DEG for both orientations of the Hall bar –along and perpendicular to the superlat-tice axis.In the latter case,shown in Fig.1(a),the peak mobility of the 2DEG is ∼25000cm 2/Vs.Our measure-ments have been carried out in magnetic ﬁelds up to 15T at T ≃50mK.The experiments have been performed at large electron densities:N s from 1×1012to 5×1012cm −2.In magnetic ﬁeld parallel to the plane of the 2DEG2FIG.1:(a)A schematic diagram showing the geometry of thestudied sample in the case of the Hall-bar oriented perpendic-ular to the super-lattice axis.(b)Density of states of 2DEG in a vicinal sample with super-lattice potential at the surface.D 0is unperturbed density of states (as in (100)Si MOSFETs),and ∆is the minigap width.(c-d)Longitudinal conductivity versus in-plane magnetic ﬁeld for diﬀerent electron densities (symbols),with linear ﬁts (solid lines).we have observed negative MC in the entire range of N s .An example is shown in Fig.1(c,d)for the Hall bar oriented parallel to the superlattice axis.In the whole range of ﬁelds the conductivity decreases linearly with B ||.The slope of this linear dependence decreases mono-tonically with increasing density up to N s ∼2.5×1012cm −2,which is close to N ′∆,Fig.1(c).However,at larger densities the slope starts changing nonmonotonically,as seen in Fig.1(d).It is important to emphasise that MC remains linear in the entire density range.In Fig.2we show the conductivity measured as a function of electron density at diﬀerent magnetic ﬁelds from 0to 15T,for both Hall-bar orientations.In zero magnetic ﬁeld the so called “Ω”-and “W”-features are clearly seen in σxx (N s )for the two orientations,respec-tively (the names reﬂect the shapes of the two depen-dences in the minigap).These well known features were previously observed in vicinal systems 3,4.They originate from the superlattice structure of the vicinal surface and indicate the very good quality of our samples.One can notice that the eﬀect of magnetic ﬁeld on the conductivity is minimal in the characteristic points cor-responding to the lower and upper boundaries of the su-perlattice minigap,N ′∆and N ′′∆,marked by the vertical dotted lines in Fig.2(a,b).This is seen for both Hall-bar orientations and corresponds to the non-monotonic dependence of the linear MC on electron density in Fig.1(b).Also,a transformation of the “W”and “Ω”fea-tures is seen in Fig.2(a,b)–these features seem to be signiﬁcantly weakened when a strong in-plane magnetic ﬁeld is applied.To analyse the linear MC let us ﬁrst consider the rangeN s <N ∆s ,where,as mentioned above,the properties of a 2DEG near the vicinal surface and the (100)surface are expected to be equivalent.Also,it is well estab-lished that scattering in the low density regime is dom-inated by impurity scattering rather than by interface roughness 3.In this region of N s the slope of the linear MC decreases monotonically with increasing density as it has been shown above.Among several models of negative parallel-ﬁeld MC 12,there are two which indeed predict linear MC:one is the interaction theory by Zala,Narozhny and Aleiner 10,and the other one is the screening model by Dolgopolov and Gold 8.We start our consideration from the interac-tion theory,which addresses the eﬀect of in-plane mag-netic ﬁeld on quantum correction to conductivity due to electron-electron (e −e )interactions in 2D disordered sys-tems.This theory predicts linear MC in relatively strong magnetic ﬁelds and in the ballistic regime,when the pa-rameter k B T τ/¯h ≫1.According to Ref.[10]the strong ﬁeld criterium (g ∗µB B ||/2k B T ≫1,where g ∗-Lande g-factor,µB -the Bohr magneton)is realised in our exper-iment already at B ||>0.3T.However the values of the parameter k B T τ/¯h range from 0.003to 0.015,implyingFIG.2:Density dependence of the conductivity at diﬀerent in-plane magnetic ﬁelds:B ||=0,2,4,6,8,10,12,15T;(a)for the Hall-bar oriented perpendicular to the supperlattice axis,(b)along the supperlattice axis.The dotted lines markthe boundaries of the superlattice minigap at N ′∆and N ′′∆.3that the system is in the diﬀusive regime,k B Tτ/¯h≪1. The estimation of MC caused by electron interactions in this regime10shows that eﬀect of e−e interactions is neg-ligible,as the magnitude of MC(proportional to ln(B)) raises to only about1%at B||∼10T.In the screening model8,9,developed for the system with isotropic Fermi surface and at T=0,the MC eﬀect originates from the change in the screening of scattering potential caused by the diﬀerence between Fermi momenta k F−and k F+for the two spin-split sub-bands.It predicts the change of the Drude conductivity with the following negative MC in the low-density case, q s≫2k F,where q s is the screening wave number.At small magneticﬁelds B||such that B||<0.2B S,where B S=2E F/g∗µB is theﬁeld of the full spin polarisation, this MC is linear in the case of short-range impurity scat-tering:σ(B||<0.2B S)B S,(1)where the coeﬃcientαvaries in the range from0.87to 0.68for the electron densities from N s=1×1012to 5×1012cm−2,Ref.[8-9].As the latter is the range of N s of our experiment,we take the average value of α=0.78for the approximate analysis.In our case q s/2k F∼2−4which justiﬁes the approx-imation of the low density.To justify the applicability of the theory developed for T=0,we only analyse quanti-tatively the data at the lowest temperature T=50mK. Simple estimation using standard parameters for(100)Si MOSFETs(g∗∼2.5,m∗=0.19m e)gives then10−15% magnetoconductivity in magneticﬁeld B∼15T,which is close to what is seen in Fig.1(a).The screening theory analyses the eﬀect of magneticﬁeld in both cases of im-purity and roughness scattering provided B||=B S,Ref.[9].However,the expression for the smallﬁeld MChas been obtained only for the impurity scattering,Eq.(1). As aﬁrst approximation,we analyse the slope of the linear dependence in the whole range of electron densities using Eq.(1)and neglecting the inﬂuence of interface-roughness scattering.It follows from the above deﬁnitionof B S that B−1S ∝g∗m∗and hence it is proportional tothe spin susceptibility of the electron gasχ.(Indeed,for a2DEG in a Si MOSFET E F=π¯h2N s/2m∗andχ= 2µ2B g∗m∗/π¯h23).The electron density is known from the measurements of Shubnikov–de Haas(SdH)oscillations. From the slope of the linear MC the product g∗m∗is then found and normalised by g0m b,where m b=0.19m e is bulk electron mass(m e is the free electron mass)and g0=2.0is the Lande g-factor in bulk silicon.The data for the both Hall-bar orientations are plotted in Fig.3(a, b).In Fig.3(a)we also show the g∗m∗results obtained by three diﬀerent experimental groups using the analysis of SdH oscillations in ordinary(100)Si MOSFETs13,14,15. At lower densities our results show a monotonic increase of spin susceptibility with decreasing N s.This trend at N s≤2.3×1012cm−2as well as the magnitude of g∗m∗agree well with the previous results.The above range is FIG.3:(a,b)Density dependence of the product g∗m∗(pro-portional to spin susceptibilityχ)normalised by the product of the bulk parameters g0m b:(a)for the Hall bar oriented perpendicularly to the superlattice axis,(b)along this axis. Data for(100)Si MOSFETs:(◦)-from Ref.[13],(•)-from Ref.[14],(+)-from Ref.[15].(c)Density dependence of the conductivity at B=0for the Hall-bar in case(a)(the same data as in Fig.2(a).exactly theﬁrst range of N s we referred to before(N s< N′∆),where the Fermi surface of the vicinal sample is isotropic,as it is in the case of(100)Si,and where the screening theory is valid.This result also indicates that in this range of N s the eﬀect of the interface-roughness scattering is negligible.A strong deviation from the monotonic behaviour of spin susceptibility is observed at larger densities(N s> N′∆)if the analysis is carried out using the same ap-proach as above.A drop of g∗m∗by more than a factor of two is seen at two diﬀerent N s for the Hall-bar oriented perpendicularly to the superlattice axis,Fig.3(a).The two minima also appear for the other Hall-bar orientation (along the superlattice axis),Fig.3(b),although they are less pronounced,presumably because of the smaller mo-bility of this sample(the diﬀerence in the conductivities is seen in Fig.2).It is clearly seen from the compar-ison to Fig.3(c)that these minima coincide with the dips of the“Ω”and“W”features inσ(N S)–the points where the Fermi level crosses the boundaries of the su-perlattice minigap.(The pronounced decrease of MC at these points is also seen in Fig.2a,b.)It is important to notice that the changes of the conductivity with N s at the minigap boundaries do not exceed10%,Fig.2, while a much more drastic decrease is seen in the density4FIG.4:(a)Typical dispersion relation for a 2DEG in a Si vicinal system 4.(b-e)Fermi surfaces at diﬀerent positions of the Fermi level E F marked by horizontal dotted lines in (a).dependence of the spin susceptibility.We have to note,however,that the screening theory is not expected to be valid in the range of N s >N ′∆.At the same time,it is seen in Fig.3(a)that in the middle of the minigap the obtained values of g ∗m ∗are close to those obtained for (100)Si using SdH oscillations.This points out that the anomalies in the MC arise only at the boundaries of the minigap.Let us discuss possible reasons for the dramatic de-crease of the MC at the minigap boundaries.A typical dispersion relation of the vicinal system in Si is shown in Fig.4(a).Diﬀerent conﬁgurations of the Fermi surfaceare shown in Fig.4(b-e)for four positions of the Fermi level.It is seen on the plot that the boundaries of the minigap in the spectrum correspond to the topological transitions of the Fermi surface:ﬁrstly the two isotropic and independent FSs coalesce (Fig.4c),and then they form two inclosed surfaces (Fig.4e).It is known that the conductivity and thermopower of the electron system is strongly modiﬁed at the points of the topological tran-sitions (N s =N ′∆,N ′′∆)4,7.In our case we see a strong decrease of the linear MC at these points.The exact theory of MC for complicated FS is not developed.However,if one assumes that the screening theory 8,9can still be applied at the boundaries of the minigap,our results indicate that the spin susceptibility sharply decreases in the points of the topological tran-sitions.Continuing this logic,it is important to note that previous investigations 11have shown that the den-sity of states at the minigap boundaries changes only within 10%,which would correspond to a small change in the eﬀective mass.This implies that it is mainly the g-factor that is aﬀected by the topological transitions in the 2DEG spectrum of the vicinal system.An increase of the g-factor,caused by enhanced ex-change interaction,is well known 16.In contrast,in our case a signiﬁcant decrease of g ∗(by a factor of two)is observed.This eﬀect could possibly be caused by the strong inter-valley interaction in the vicinal struc-ture (giving rise also to the “Ω”and “W”features in the conductivity 3).We have to say,however,that the above speculations are based on the assumption that the screening theory 8,9is applicable within the minigap.An appropriate theory for such a case does not exist at the moment,and we hope that our experiments will stimu-late its development.This work was supported by Royal Society,RFBR (grant 02-02-16516),INTAS (project 01-0014),Russian Ministry of Education (program “Integration”)and RAS (program “Low dimensional quantum structures”),EP-SRC and ORS scheme.*Current address:Physics Department,Royal Hol-loway,University of London,Egham,Surrey,TW200EX,U.K.1E.Abrahams et al.,Rev.Mod.Phys.73,251(2001).2L.J.Sham et al.,Phys.Rev.Lett.40,472(1978).3T.Ando,A.Fowler,F.Stern.Rev.Mod.Phys.,54,437(1982).4V.A.Volkov et al.,p.23,375(1980).5T.G.Matheson and R.J.Higgins,Phys.Rev.B 25,2633(1982).6R.Kaplan,Phys.Semicond.(Inst.Phys.Conf.Ser.Lnd.)No.43,1351(1979).7N.V.Zavaritsky,Z.D.Kvon,JETP Lett.,39,71,(1984).8V.T.Dolgopolov and A.Gold,JETP Lett.71,27(2000).9A.Gold and V.T.Dolgopolov,Physica E 17,280(2003).10G.Zala et al.,Phys.Rev.B 65,020201(2001).11A.A.Bykov et al.,Sov.Phys.Semicond.22,1077(1988).12B.L.Altshuler et al.,Phys.Rev.Lett.82,145(1999);Y.Meir,Phys.Rev.Lett.83,3506(1999);S.Das Sarma and E.H.Hwang,Phys.Rev.Lett.84,5596(2000);I.F.Herbut,Phys.Rev.B 63,113102(2001);V.I.Kozub and N.V.Agrinskaya,Phys.Rev.B 64,245103(2001).13F.F.Fang and P.J.Stiles,Phys.Rev.174,823(1968).14V.M.Pudalov et al.,Phys.Rev.Lett.88,196404(2002).15T.Okamoto et al.,Phys.Rev.Lett.82,3875(1999).16G.-H.Chen and M. E.Raikh,Phys.Rev.B 60,4826(1999),and references therein.。

核磁共振波普仪器专业词汇英汉翻译

APT Attached Proton Test 质子连接实验ASIS Aromatic Solvent Induced Shift 芳香溶剂诱导位移BBDR Broad Band Double Resonance 宽带双共振BIRD Bilinear Rotation Decoupling 双线性旋转去偶（脉冲）COLOC Correlated Spectroscopy for Long Range Coupling 远程偶合相关谱COSY ( Homonuclear chemical shift ) COrrelation SpectroscopY （同核化学位移）相关谱CP Cross Polarization 交叉极化CP/MAS Cross Polarization / Magic Angle Spinning 交叉极化魔角自旋CSA Chemical Shift Anisotropy 化学位移各向异性CSCM Chemical Shift Correlation Map 化学位移相关图CW continuous wave 连续波DD Dipole-Dipole 偶极-偶极DECSY Double-quantum Echo Correlated Spectroscopy 双量子回波相关谱DEPT Distortionless Enhancement by Polarization Transfer 无畸变极化转移增强2DFTS two Dimensional FT Spectroscopy 二维傅立叶变换谱DNMR Dynamic NMR 动态NMRDNP Dynamic Nuclear Polarization 动态核极化DQ(C) Double Quantum (Coherence) 双量子（相干）DQD Digital Quadrature Detection 数字正交检测DQF Double Quantum Filter 双量子滤波DQF-COSY Double Quantum Filtered COSY 双量子滤波COSY DRDS Double Resonance Difference Spectroscopy 双共振差谱EXSY Exchange Spectroscopy 交换谱FFT Fast Fourier Transformation 快速傅立叶变换FID Free Induction Decay 自由诱导衰减H,C-COSY 1H,13C chemical-shift COrrelation SpectroscopY 1H,13C 化学位移相关谱H,X-COSY 1H,X-nucleus chemical-shift COrrelation SpectroscopY1H,X-核化学位移相关谱HETCOR Heteronuclear Correlation Spectroscopy 异核相关谱HMBC Heteronuclear Multiple-Bond Correlation 异核多键相关HMQC Heteronuclear Multiple Quantum Coherence异核多量子相干HOESY Heteronuclear Overhauser Effect Spectroscopy 异核Overhause效应谱HOHAHA Homonuclear Hartmann-Hahn spectroscopy 同核Hartmann-Hahn谱HR High Resolution 高分辨HSQCHeteronuclear Single Quantum Coherence 异核单量子相干INADEQUATE Incredible Natural Abundance Double Quantum Transfer Experiment 稀核双量子转移实验（简称双量子实验，或双量子谱）INDOR Internuclear Double Resonance 核间双共振INEPT Insensitive Nuclei Enhanced by Polarization 非灵敏核极化转移增强INVERSE H,X correlation via 1H detection 检测1H的H,X核相关IR Inversion-Recovery 反（翻）转回复JRES J-resolved spectroscopy J-分解谱LIS Lanthanide (chemical shift reagent ) Induced Shift 镧系（化学位移试剂）诱导位移LSR Lanthanide Shift Reagent 镧系位移试剂MAS Magic-Angle Spinning 魔角自旋MQ(C) Multiple-Quantum ( Coherence ) 多量子（相干）MQF Multiple-Quantum Filter 多量子滤波MQMAS Multiple-Quantum Magic-Angle Spinning 多量子魔角自旋MQS Multi Quantum Spectroscopy 多量子谱NMR Nuclear Magnetic Resonance 核磁共振NOE Nuclear Overhauser Effect 核Overhauser效应（NOE）NOESY Nuclear Overhauser Effect Spectroscopy 二维NOE谱NQR Nuclear Quadrupole Resonance 核四极共振PFG Pulsed Gradient Field 脉冲梯度场PGSE Pulsed Gradient Spin Echo 脉冲梯度自旋回波PRFT Partially Relaxed Fourier Transform 部分弛豫傅立叶变换PSD Phase-sensitive Detection 相敏检测PW Pulse Width 脉宽RCT Relayed Coherence Transfer 接力相干转移RECSY Multistep Relayed Coherence Spectroscopy 多步接力相干谱REDOR Rotational Echo Double Resonance 旋转回波双共振RELAY Relayed Correlation Spectroscopy 接力相关谱RF Radio Frequency 射频ROESY Rotating Frame Overhauser Effect Spectroscopy 旋转坐标系NOE谱ROTO ROESY-TOCSY Relay ROESY-TOCSY 接力谱SC Scalar Coupling 标量偶合SDDS Spin Decoupling Difference Spectroscopy 自旋去偶差谱SE Spin Echo 自旋回波SECSY Spin-Echo Correlated Spectroscopy自旋回波相关谱SEDOR Spin Echo Double Resonance 自旋回波双共振SEFT Spin-Echo Fourier Transform Spectroscopy (with J modulation)（J-调制）自旋回波傅立叶变换谱SELINCOR Selective Inverse Correlation 选择性反相关SELINQUATE Selective INADEQUATE 选择性双量子（实验）SFORD Single Frequency Off-Resonance Decoupling 单频偏共振去偶SNR or S/N Signal-to-noise Ratio 信 / 燥比SQF Single-Quantum Filter 单量子滤波SR Saturation-Recovery 饱和恢复TCF Time Correlation Function 时间相关涵数TOCSY Total Correlation Spectroscopy 全（总）相关谱TORO TOCSY-ROESY Relay TOCSY-ROESY接力TQF Triple-Quantum Filter 三量子滤波WALTZ-16 A broadband decoupling sequence 宽带去偶序列WATERGATE Water suppression pulse sequence 水峰压制脉冲序列WEFT Water Eliminated Fourier Transform 水峰消除傅立叶变换ZQ(C) Zero-Quantum (Coherence) 零量子相干ZQF Zero-Quantum Filter 零量子滤波T1 Longitudinal (spin-lattice) relaxation time for MZ 纵向（自旋-晶格）弛豫时间T2 Transverse (spin-spin) relaxation time for Mxy 横向（自旋-自旋）弛豫时间tm mixing time 混合时间τc rotational correlation time 旋转相关时间。

巨磁电阻传感器

The magnetoresistance is the change of electrical resistance of a conductor when subjected to an external magnetic field. In bulk ferromagnetic conductors, the leading contribution to the magnetoresistance is due to the anisotropic magnetoresistance (AMR) discovered in 1857 by W. Thomson (Lord Kelvin) (Proc. R. Soc. London A8, 546 (1857)). This originates from the spin-orbit interaction, which leads to a different electrical resistivity for a current direction parallel or perpendicular to the magnetization direction. As a magnetic field is applied, misoriented magnetic domains tend to align their magnetization along the field direction, giving rise to a resistance change of the order of a few percent. Magnetoresistive effects are of great interest for industrial applications, and the AMR has been applied for making magnetic sensors and read-out heads for magnetic disks. Until 1988, the 130 years old AMR remained the most important contribution to the magnetoresistance of ferromagnets. The situation at that time is best summarized by the following pessimistic quotation, taken from an authorative treatise on magnetic sensor technology written in 1988: “More t han t wo decades of research and development have established the principle of magnetoresistive sensors. (...). It is doubtful, however, whether magnet oresist ive layers t hemselves will be improved considerably in t he coming years.”(From“Sensors, A Comprehensive Survey, Vol. 5: Magnetic Sensors”, VCH (1989)).It was therefore a great sensation when, in 1988, Albert Fert and Peter Grünberg independently discovered that a much greater magnetoresistive effect (hence dubbed “giant magnetoresistance” or GMR) can be obtained in magnetic multilayers. These systems essentially consist of an alternate stack of ferromagnetic (e.g., Fe, Co, Ni, and their alloys) and non-ferromagnetic (e.g., Cr, Cu, Ru, etc.) metallic layers. Each individual layer in these multilayers is only a few atomic layers thick. Fert and Grünberg discovered that when the relative orientation of the magnetization of the successive ferromagnetic layers is changed from antiparallel to parallel by applying an external magnetic field, the electrical resistance of the multilayers is reduced by as much as 50% as shown schematically in Figure 1.Fig. 1. Schematic description of the giant magnetoresistance effect. Blue curve:magnetization of the multilayer versus applied magnetic field. Red curve:electricalresistance of the multilayer. The insets indicate the magnetic configuration of themultilayer in zero field and at positive and negative saturation fields.The phenomenon of GMR results from a combination of two physically distinct new effects. The first one is the very fact that the electrical resistance of the multilayer varies considerably as the configuration is switched from parallel (P) to antiparallel (AP). This effect arises as a consequence of the spin-dependent scattering of electrons in ferromagnetic layers, which in the 70’s has been intensively studied by Albert Fert in bulk ferromagnets and ferromagnetic alloys. This effect is shown schematically in Figure 2.The second important new effect is the antiferromagnetic interlayer exchange coupling (discovered by Peter Grünberg in 1986), which leads to an antiparallel orientation of the magnetizations of successive ferromagnetic layers in absence of an external field; this effect allows one (by applying an external magnetic field) to effectively switch from the AP configuration to the P configuration, and thus to reveal the GMR phenomenon.Fig. 2. Schematic description of the spin-dependent scattering mechanism for thegiant magnetoresistance. Electrons are strongly scattered in magnetic layers withmagnetizations (white arrows) antiparallel to their spin (black arrows), and weaklyscattered in magnetic layers with magnetizations parallel to their spin. This results ina short-circuit effect in the P configuration, where half of the electrons are seldomscattered, yielding a lower net resistance.The GMR has originally been discovered in the “current-in-plane” (CIP) configuration, which is the easiest to study experimentally. Later, it was shown that an even larger effect takes place in the “current-perpendicular-to-plane” (CPP) configuration.3. Scientific contributions of Albert FertLong before the discovery of giant magnetoresistance, the study of spin-polarized electronic transport in magnetic materials has been a major research topic of Albert Fert. In the 70’s, together with I.A. Campbell, he performed pioneering studies on the resistivity of ferromagnetic alloys (Phys. Rev. Lett. 21, 1190 (1968)∗; J. de Physique C1-32, 1 (1971); J. Phys. F 6, 849 (1976)). In these studies, he developed the concepts of spin-dependent currents (originally suggested by Mott), of spin-dependent resistivity and spin-dependent scattering, which later became the key conceptual ingredients of the GMR effect.∗The references marked in blue are linked via internet to the corresponding paper. Depending on the online subscription of your institution, you may either have access to the full text or only to the abstract.In the mid-80’s, Albert Fert started working on magnetic multilayers, and his experience with spin-polarized transport in magnetic alloys prompted him to focus on their electronic transport properties. He soon realized that the effect of spin-dependent scattering would give rise to magnetoresistance effects of unprecedented magnitude, provided one finds a mean to switch the relative orientation of the magnetization of successive magnetic layers in a multilayer from parallel to antiparallel. That this idea was indeed correct was further suggested by observations of J.-P. Renard’s group who reported small but striking anomalies in the resistivity of uncoupled Co/Au magnetic multilayers at the coercive field (Physica Scripta T19, 405 (1987); Phys. Rev. B 37, 668 (1988)). The missing link for obtaining a strong magnetoresistance was provided by exploiting Grünberg’s discovery of antiferromagnetic exchange coupling in magnetic multilayers (Phys. Rev. Lett. 57, 2442 (1986)).In 1988, Albert Fert and his coworkers discovered a giant magnetoresistance effect (about 50% change in resistance) in Fe/Cr multilayers (see Figure 3) (Phys. Rev. Lett. 61, 2472 (1988)). Fert’s article reporting the discovery of the giant magnetoresistance has been cited about 2500 times in the literature. The same effect was also discovered independently and simultaneously by Peter Grünberg (Phys. Rev. B 39, 4828 (1989)) (see next Section). Later on, by using more complex multilayers comprising materials of suitable spin-asymmetric scattering, Fert and his coworkers were able to produce an inverse GMR effect (Phys. Rev. Lett. 72, 408 (1994)).Besides the experimental discovery of the GMR, Albert Fert was also very active in developing theoretical concepts to explain the GMR effect. Together with P.M. Levy and S.F. Zhang, he worked out the first quantum mechanical theory of the GMR (Phys. Rev. Lett.65, 1643 (1990)). He also proposed a theory of the CPP-GMR (Phys. Rev. B 48, 7099 (1993)) (now a classic known as the Valet-Fert model), in which he pointed out the importance of spin-flip processes and of the concept of spin accumulation. Those ideas were confirmed experimentally by investigating the magnetoresistance of multilayered nanowires in collaboration with L. Piraux (Appl. Phys. Lett. 65, 2484 (1994)).Albert Fert and his coworkers also made important contributions on the topic of tunneling magnetoresistance: they were the first to show that the tunneling magnetoresistance can reach huge values when the electrodes consist of half-metallic materials (J. Magn. Magn. Mater.199,1 (1999)) and that the sign and amplitude of the tunneling magnetoresistanceratio do not only depend on the electrodes, but also on the barrier material (Science286, 507 (1999)).From the theoretical point of view, Albert Fert (together with J. Barnas) considered the interplay between tunneling magnetoresistance and the Coulomb blockade in magnetic nanostructures and predicted striking new effects (Phys. Rev. Lett. 80, 1058 (1998)), thereby opening a new direction of development for single electron transistors (SET).Fig.3.Giant magnetoresistance of Fe/Cr multilayers, reported by Albert Fert’s group(Phys. Rev. Lett. 61, 2472 (1988)).Most recently, Albert Fert’s group addressed the problem spin-current-induced magnetic switching (Appl. Phys. Lett. 78, 3663 (2001)), one of the new hot topics in spin-electronics.4. Scientific Contributions of Peter GrünbergPrior to 1986 Peter Grünberg had a long-standing record of improving the growth and of characterizing the properties of magnetic layers. In particular he developed the Brillouin scattering technique to such a precision, that he could detect surface magnons and standing spinwaves down to monolayer thicknesses. Based on this experience, he started studying the exchange coupling of two ferromagnetic iron layers separated by non-magnetic metallic interlayers. This culminated 1986 in the pioneering letter (Phys. Rev. Lett.57, 2442 (1986)) reporting the discovery of interlayer exchange coupling in transitionmetal systems. Using Brillouin scattering he could unambiguously show that two Fe layers separated by a Cr interlayer couple for certain Cr thicknesses antiparallel to each other and can be aligned parallel to each other by applying an external magnetic field. All previous experiments had obtained only ferromagnetic coupling due to Fe “pinholes” penetrating the Cr layers.Fig. 4. Giant magnetoresistance of Fe/Cr/Fe bilayers, reported by Peter Grünberg’sgroup (Phys. Rev. B 39, 4828 (1989)). Upper panel: Magnetization curve (theBrillouin spectra in inset show the AP configuration of Fe layers in zero field). Lowerpanel:Electrical resistance (the lower curve shows the much smaller AMR of a singleFe layer).This discovery initiated substantial experimental and theoretical studies. Two years later, Peter Grünberg and his co-workers discovered, independently and simultaneously with the Fert group, the Giant Magnetoresistance (GMR) effect in Fe/Cr layers (Phys. Rev. B 39, 4828 (1 March 1989), received there already 31 May, 1988). Contrary to Fert, who studied an Fe/Cr multilayer, Grünberg investigated an Fe/Cr/Fe trilayer and obtained therefore a smaller GMR value of 1.5 % at room temperature (see Figure 4). Grünberg’spapers reporting the discoveries of the antiferromagnetic interlayer coupling (1986) and of the giant magnetoresistance (1989) have received more than 800 and 650 citations, respectively.While Albert Fert directly offered in his publication the correct explanation of the GMR effect in terms of spin-dependent scattering, Peter Grünberg immediately realized the prospect of interesting technological applications and applied for a patent, firstly (1988) in Germany (DE 3820475), then in Europe (0346817) and the USA (4,949,039). It turned out to be a very comprehensive patent, which has been acknowledged worldwide by all major companies, and which is now seen as the key patent for Magnetoelectronics. How farsighted Grünberg’s ideas were, shows up by the long time span of seven years, before first license fees came in. How important the patent is, shows up in the strong increase of license fees, which up to 2001 amounted to a total of 10.5 million $. At present there exist worldwide about thousand patents in the field of Magnetoelectronics/Spin-electronics. This best characterizes the rich technological harvest expected in this field, all originating from the discovery of the GMR effect.The antiparallel arrangement of the two ferromagnetic layers, which is essential for the GMR effect, can also be realized in the non-coupling case, as was demonstrated by Grünberg and co-workers (Phys. Rev. B 42, 8110 (1990)) as well as C. Dupas et al. (J. Appl. Phys. 67, 5680 (1990)) and T. Shinjo et al. (J. Phys. Soc. Japan 59, 3061 (1990)) by using hard and soft magnetic layers. Another realization consists in using an antiferromagnet in direct contact, known as “exchange biasing”. In the literature these systems are referred to as “spin valve systems”, although there is no difference with respect to the GMR effect.Another important contribution of Grünberg, this time achieved in collaboration with the group of A. Hubert, was the discovery of the bi-quadratic coupling (phys. stat. sol. (a) 125, 635 (1991)). This is an anharmonic exchange interaction being quadratic in the scalar product M1.M2 of the two moments and is particularly important for layered systems. It can favor a 90° alignment of the magnetic layers and shows up in a region of spacer thicknesses between the ferro- and antiferromagnetic coupling. There are several other important contributions by Peter Grünberg. For instance, he was one of the firsts toobserve the short period of interlayer coupling in Fe/Cr and first reported multiperiodic oscillatory coupling in Fe/Au/Fe systems.Present work of Grünberg includes silicon and silicide interlayers (Phys. Rev. Lett., 87, 157202 (2001)) which can mediate surprisingly strong antiferromagnetic interlayer coupling.5. Emergence of a new field: Spin ElectronicsIn the aftermath of the discovery of the giant magnetoresistance, a tremendous research activity has been initiated, both in academic and industry institutes, involving several thousands of researchers worldwide, in order to exploit the potential revealed by Fert and Grünberg. A number of important discoveries, which will be briefly reviewed below, followed rapidly. This new field of research has been named spin electronics (also magnetoelectronics, or spintronics). In its most precise definition, spin electronics refers to new phenomena of electronic transport, in which the spin of the electron plays a central active role (in contrast to conventional electronics, for which the electron spin is essentially irrelevant). In practice, a somehow looser definition is frequently accepted (including new phenomena not directly related to transport). While it is fair to mention that some of the topics listed below already started before 1988, the discovery of the GMR undoubtedly contributed in a decisive manner to reveal their great potential and to reach their full impact.Oscillatory interlayer exchange couplingThe most spectacular development in the field of interlayer exchange coupling is due to S.S.P. Parkin who discovered that the interlayer coupling exhibits a remarkable oscillatory behavior as a function of the interlayer thickness (Phys. Rev. Lett. 64, 2304 (1990);Phys. Rev. Lett. 67, 3598 (1991)). This discovery stimulated an important experimental and theoretical activity. It culminated with impressive experiments by J. Unguris et al.(Phys. Rev. Lett. 67, 140 (1991);Phys. Rev. Lett. 79, 2734 (1997)). Theoretically, this effect, which is related to the Ruderman-K ittel-K asuya-Yosida (RK K Y) interaction between magnetic impurities in a non-magnetic metal, could be successfully interpreted as a quantum size effect due to spin-dependent electron confinement, and excellentquantitative agreement between theoretical predictions and experimental observations was obtained. From the practical point of view, the oscillatory interlayer coupling provides an outstanding tool for the quantum engineering of the magnetic properties of multilayers.Tunneling magnetoresistanceGiant magnetoresistance effects have also been found in systems comprising an insulating tunneling junction sandwiched between two ferromagnetic metallic electrodes. Early pioneering investigations on the problem of spin-dependent tunneling were performed in the 70’s by P.M. Tedrow and R. Meservey (Phys. Rev. B 7, 318 (1973)), by M. Jullière (Phys. Lett. 54A, 225(1975)), and by S. Maekawa and U. Gäfvert (IEEE Trans. Magn.18, 707 (1982)). However, they attracted little attention for more almost 20 years. Renewed interest was triggered recently, on one hand by the progress in technology (allowing to fabricate reliable and reproducible tunnel junctions without pinholes), and on the other hand by the discovery of GMR in metallic multilayers. Large magnetoresistance in magnetic tunnel junctions were observed at room temperature by J.S. Moodera (Phys. Rev. Lett. 74, 3273 (1995)) and T. Miyazaki (J. Magn. Magn. Mater. 139, L231 (1995)), followed by many other groups. On the theoretical point of view, the mechanism was explained on the basis of a simple model originally proposed by Jullière, and later developed by other authors. Modern theoretical approaches, based upon sophisticated ab initio methods now allow accurate quantitative predictions. The industrial potential of the tunneling magnetoresistance will be presented in the next Section below.Colossal magnetoresistanceIn 1994, S. Jin et al. discovered an even larger magnetoresistive effect in mixed valence manganese perovskites (Science264, 413 (1994)). The change of resistance under magnetic field reaches several orders of magnitudes in this class of materials, so that the effect was dubbed colossal magne oresis ance (CMR). Although the materials were known since the 50’s, and in spite of important pioneering contributions by Zener and de Gennes, their extraordinary magnetoresistive property remained elusive for almost half a century. The discovery of the CMR attracted a considerable attention, and a large part of the scientific community working on high-temperature superconductivity moved to this newfield. This class of materials reveals an exceptionally rich variety of physical properties, in which electronic correlations, spin and orbital ordering play an essential role.Half-metallic materialsThe efficiency of spin electronic effects depend strongly on the degree of spin-polarization of the density of states of the magnetic materials at the Fermi energy: the higher the spin-polarization, the stronger the magneto-electronic effects. It is therefore of great interest to find materials with a high spin-polarization. In 1983, de Groot et al. theoretically predicted the existence of a new class of materials, called half-metallic ferromagnets, in which one spin-subband is metallic and the other spin-subband is insulating (Phys. Rev. Lett. 50, 2024 (1983)). Those materials therefore have 100% spin-polarization at Fermi energy. Soon after the discovery of the GMR, the interest of half-metallic ferromagnets for spin-electronics became obvious. Half-metallic character was first confirmed experimentally for CrO2(Phys. Rev. Lett. 59, 2788 (1987);Phys. Rev. Lett. 86, 5585 (2001)). Enhanced magnetoresistance was indeed reported for half-metallic CrO2 (Science278, 1607 (1997)).Magnetic semiconductorsIn order to fully exploit the potential of spin electronics, it is desirable to have some materials that are simultaneously semiconducting and magnetic. As soon as this was realized, people started to search actively for magnetic semiconductors with high Curie temperature (ideally, the latter should be well above 300 K). Major progress in this field was achieved by the group of H. Ohno, who reached a Curie temperature of 110 K in (Ga,Mn)As (Science281, 951 (1998)) and proved the possibility of an electric control of the Curie temperature by means of a gate voltage (Nature408, 944 (2000)). Intense research (both experimental and theoretical) on this problem, which is considered to be of major importance, is currently going on.Spin injectionWhen electrons are injected from a ferromagnet into a non-magnetic material they can retain their spin polarization over a certain distance. This effect is called spin-injection and can be used to create new electronic devices. This was first demonstrated by M. Johnsonwho, after some pioneering work in the mid-80’s (Phys. Rev. Lett. 55, 1790 (1985)), succeeded in operating an all-metal bipolar spin t ransist or(Science260, 320 (1993)). Later on, a great effort was devoted to performing spin injection from a metallic ferromagnet into a semiconductor. This turned out to be extremely difficult, and an important obstacle was indicated; nevertheless, very recently, H.J. Zhu et al. (Phys. Rev. Lett.87, 016601 (2001)) and A.T. Hanbicki et al. (Appl. Phys. Lett. 80, 1240 (2002)) could overcome this problem and demonstrated successful spin-injection from Fe into GaAs.Spin injection into a semiconductor from a magnet ic semiconductor was alsodemonstrated by R. Fiederling et al. (Nature402, 787 (1999)) and by Y. Ohno et al. (Nature402, 790 (1999)), but this requires very low temperatures and/or an external magnetic field.Spin transport in semiconductorsA further aspect of great importance is whether spin-polarized electrons can be transported through semiconductors without losing their spin polarization. Major progress on this problem was achieved in particular by the group of D.D. Awshalom who demonstrated that electrons can retain their spin polarization over unexpectedly long times and distances (Science277, 1284 (1997);Nature411, 770 (2001);Science292, 2458 (2001)).Magnetic switching induced by spin-currentIn 1996, J.C. Slonczewski (J. Magn. Magn. Mater. 159, L1 (1996)) and L. Berger (Phys. Rev. B 54, 9353 (1996)) theoretically pointed out that a spin-polarized current driven through a magnetic multilayer creates a torque on the magnetic layers, which can lead to a magnetization reversal. This provides a completely new method for writing information in a magnetic memory. The prediction was first confirmed experimentally by E.B. Myers et al. (Science285, 867 (1999)), J.A. Katine et al. (Phys. Rev. Lett. 84, 3149 (2000)), and F.J. Albert et al. (Appl. Phys. Lett. 77, 3809 (2000)).6. Industrial ApplicationsIt is unusual that a basic effect like GMR leads in less than a decade after discovery to commercial applications. A decisive step for applications was Parkin’s discovery that GMR with a large magnetoresistance ratio at room temperature can be obtained in multilayers prepared by sputtering (Phys. Rev. Lett. 66, 2152 (1991);Appl. Phys. Lett. 58, 2710 (1991)). Magnetic field sensors based on GMR were already introduced as soon as 1996 by Non-Volatile Electronics and in 1997 by Siemens, aiming at applications in mechanical and automotive industries for monitoring machinery operations. For instance, if a GMR-sensor is placed close to a rotating ferrous gear, the moment direction of the soft magnetic sensor layer can switch every time a gear tooth passes the sensor, if the field induced by the gear exceeds a critical value. Such sensors can be used as a contactless potentiometer or to measure angles or distances. There are many other interesting applications of GMR sensors, e.g. in connection with a highly magnetostrictive layer as strain sensor or as actuator, or as magnetocouplers for the galvanic separation of signals, presently the domain of optocouplers. A particular interesting application is the use in biochips. Here magnetic particles are coated with a suitable antibody that will only bind to a specific analyte (virus, bacteria, etc.). By using an array of GMR sensors individually coated with the specific antibody of interest, the analyte will bind to the sensor, carrying with it the magnetic particle, the magnetic fringing field of which will rotate the magnetization of the sensor layer and thus change the resistance.The most important application of GMR sensors is the use as read-out heads in computer hard-disk drives (see Figure 5), being introduced in 1997 by IBM. These sensors have now replaced the AMR (Anisotropic Magnetoresistance) - based heads, because the GMR effect is larger and moreover scales better. At present they have a storage density of more than 50 Gbit/in2 (see Figure 6) and a total market volume of around $ 1 billion per year. Another fascinating invention of IBM is the Microdrive. The latest model packs 1 Gbyte of storage capacity on a disk the size of an U.S. quarter (see Fig. 7). These miniature devices aim at another mass market, i.e. handheld electronic products like digital cameras, video cameras, personal digital assistants (PDAs), etc.Fig. 5. Schematic description of a GMR read head for magnetic disks.Fig. 6. Recent evolution of the storage density of magnetic disks.Fig. 7. IBM’s ``quarter dollar´´ 1 GB Microdrive.At present the most ambitious project with potentially large economic impact is the use of magnetic tunnel junctions as non-volatile magnetic random access memories (MRAM). The present semiconductor-based memories (DRAM, SRAM, ...) are nonpermanent (volatile) and the information is lost, when the computer is switched off. An MRAM consists of two perpendicular arrays of conducting wires being connected by a tunnel junction at the crossing points (see Figure 8). The wires allow both to read the information stored in the junctions by the TMR effect as well as to switch the magnetization by the magnetic field induced by the currents. In addition to being non-volatile, MRAMs have some further advantages with respect to DRAMS, such as lower energy consumption and higher scalability, which make them particularly well suited for computers and mobile phones. The total market, at which the MRAM development aims, is huge; alone the volume of DRAM was $ 29 billion in 2000. Industrial MRAM projects exist in the USA, in Europe (Infineon in collaboration with IBM) and Japan (Hitachi, Toshiba and NEC).The two leading companies, IBM/Infineon and Motorola, plan to introduce first commercial MRAM products in 2004. In parallel to these projects also GMR-based MRAMs have been developed for aerospace applications, primarily because of their radiation hardness. Also high-density GMR-MRAM for computer applications are in development, but the TMR-based MRAMs seem to be more promising.Fig. 8. Schematic description of a magnetic random access memory (MRAM).With GMR read-out heads in widespread use and MRAM devices soon to reach the market, there are many more visionary projects, which could have a strong impact on our future electronics. The TMR or GMR sensor is already a simple logic gate, where the two magnetizations can be used to define its function as an AND, OR, NAND or NOR gate. For a set of such magnetoresistive elements, these functions can then be altered, ``on the fly´´, by merely resetting the magnetization on the appropriate elements, which could form the basis of a reprogrammable logic technology. This would basically result in a universal processor, which can be optimized for any calculational step. There are even more visionary ideas, e.g. for quantum computing. Only time can show how these visions can be transformed into real products, leading to a true spin electronics industry.SummaryThe Giant Magnetoresistance effect found independently by Albert Fert and Peter Grünberg represents the most important achievement in the field of magnetism during the last decades. It has led to a whole series of important discoveries and opened the door for a new field: spin electronics. Within the unusually short time of seven years, the fundamental discovery turned into commercially available products with huge market share. Without doubt spin electronics will be a major topic in the physics of the 21st century and will have a strong impact on information technology.。

关于电磁场的英文作文

关于电磁场的英文作文英文回答：Electromagnetic fields are a fundamental aspect of our modern world. They are all around us, from the electricity that powers our homes to the signals that allow us to communicate wirelessly. Understanding electromagneticfields is essential for many aspects of our daily lives.One of the key concepts in electromagnetism is the idea of electric and magnetic fields. These fields are invisible, but they have a significant impact on the world around us. Electric fields are created by electric charges, such asthe positive and negative charges in a battery. Magnetic fields, on the other hand, are created by moving electric charges, such as the current flowing through a wire.These fields interact with each other and with charged particles, creating a wide range of phenomena. For example, when an electric field and a magnetic field areperpendicular to each other, they can produce a force that causes a charged particle to move in a circular path. Thisis the principle behind the operation of a particle accelerator.Electromagnetic fields also play a crucial role in the transmission of information. Radio waves, for instance, are a type of electromagnetic wave that carries signals fromone place to another. We use radio waves to listen to music, talk on our cell phones, and watch television. Without electromagnetic fields, these technologies would not be possible.In addition to their practical applications, electromagnetic fields also have some interesting properties. For example, they can be described by mathematical equations known as Maxwell's equations. These equations provide a comprehensive description of howelectric and magnetic fields behave and interact with each other. They have been instrumental in the development of modern physics and engineering.中文回答：电磁场是我们现代世界的一个基本方面。

MagnTek MT6816 高分辨率无延迟磁场角度位置传感器IC说明书

Features and Benefits￭Based on advanced AMR Technology with 0~360°Full Range Angle Sensing ￭14 bit Core Resolution￭Maximum Rotation Speed 25,000 RPM ￭Output Propagation Delay <2 us￭-40~125℃ Industry Operating Temperature Range￭Output Interface: ABZ、UVW，PWM or SPI ￭Incremental ABZ Resolution 1~1024 Pulses per Revolution User Programmable ￭UVW Output Resolution 1~16 Pole-Pairs per Revolution User Programmable ￭SOP-8 PackageGeneral DescriptionTheMagnTekrotarypositionsensorMT6816is an IC based on advanced AMR technology.A rotating magnetic field in the x-y sensor plane delivers two sinusoidal output signals which indicating the angle(α)between the sensor and the magneticfield direction.The sensor is only sensitive to the magnetic field direction in x-y plane as the sensing element output is specially designed to be independent from the magnet field strength.This allows the device to be less sensitive to magnet variations,stray magnetic fields,air gap changes and off-axis misalignment.TheincrementalABZoutputmodeisavailable in this sensor series,making thechip suitable to replace various optical encoders.The maximum resolution is 4096steps or 1024pulses per revolutionA standard SPI (3-Wire or 4-Wire)interface allows a host microcontroller to read out the 14-bit absolute angle position data from MT6816.The absolute angle position is also provided as a 12bit PWM output.Applications￭Absolute Angle Position Sensor ￭BLDC Motor Control ￭Servo Motor Control ￭Stepping Motor Control ￭Optical EncoderReplacementTable of ContentsFeatures and Benefits (1)Applications (1)General Description (1)1Pin Configuration (3)2Function Diagram (4)3Absolute Maximum Ratings (5)4Operating Conditions (5)5Electrical Characteristics (6)6Magnetic Input Specifications (8)7Output Mode (9)7.1I/O Pin Configuration (9)7.2Reference Circuit for ABZ,UVW and PWM Mode (10)7.3Quadrature A,B and Zero-Position Output Signal(ABZ Mode) (11)7.4UVW Output Mode (15)7.5Pulse Width Modulation(PWM)Output Mode (16)7.6SPI Interface (17)7.6.1SPI Reference Circuit (17)7.6.2SPI Timing Diagram (18)7.6.34-Wire SPI (19)7.6.43-Wire SPI (20)7.6.5SPI Read Angle Register (21)8MTP Programming (23)9Magnet Placement (24)10Mechanical Angle Direction (25)11Package Information (26)12Copy Rights and Disclaimer (27)13Revision History (28)1. Pin Configuration3Figure 1: Pin Configuration of MT6816(SOP-8) PackagePart Number DescriptionMT6816CTSOP-8 Package, Tube Pack (100pcs/Tube) or Tape & Reel Pack (3000pcs/Reel)Family MembersPin List*SOP-8 Reflow Sensitivity Classification: MSL-3Sensing Center at Geometry Center12348765Name #Type Description CSN 1Digital Input SPI Chip SelectionHVPP 2Power Supply OTP Programming Supply（7V）or SPI Enable OUT 3Digital Output PWM Output VDD 4Power Supply 3.3~5.0V SupplyA/U 5Digital Input/output Incremental Signal A/U or SPI MOSI(4-Wire), SDAT(3-Wire)B/V 6Digital Input/output Incremental Signal B/V or SPI MISO(4-Wire)Z/W 7Digital Input Incremental Signal Z/W or SPI Clock GND8GroundGround2. Functional DiagramFigure 2: Block DiagramThe MT6816is manufactured in a CMOS standard process and uses advanced magnet sensing technology to sense the magnetic field distribution across the surface of the chip.The integrated magnetic sensing element array is placed around the center of the device and delivers a voltage representation of the magnetic field at the surface of the IC.Figure 2shows a simplified block diagram of the chip,consisting of the magnetic sensing element modeled by two interleaved Wheatstone bridges to generate cosine and sine signals,gain stages,analog-to-digital converters (ADC)for signal conditioning,and a digital signal processing (DSP)unit for encoding.Other supporting blocks such as LDO,etc.are also included.G GADCADCDSPLDO CalibrationNVMABZ /-A-B-ZPWMVDD HVPPA B ZOUTCSNM U XOSCSPIUVWVSS Angle CalculationInterpolatorMagnetic Sensing ElementI/V REF3. Absolute Maximum Ratings (Non-Operating)ParameterMin.Max.Unit NotesDC Voltage at Pin VDD -0.5 6.5V DC Voltage at Pin HVPP-0.58V Terminal Voltage at Input and Output Pins -0.5VDD V ABZ,OUT Output Current at Output Pins -2020mA ABZ, OUT Storage Temperature-55150℃Electrostatic Discharge (CDM)-±1.0KV Electrostatic Discharge (HBM)-±3.0KVStresses beyond those listed under “Absolute Maximum Ratings”may cause permanent damage to the device.These are stress ratings only.Functional operation of the device at these or any other conditions beyond those indicated under “Operating Conditions”is not implied.Exposure to absolute maximum rating conditions for extended periods may affect device reliability.4. Operating ConditionsParameterMin.Max.Unit DC Voltage at Pin VDD3.0 5.5V DC Voltage at Pin HVPP (If Used) 6.757.25V Magnetic Flux Density Range 301,000mT Rotation Speed -25,000RPM Operating Temperature-40125℃5. Electrical CharacteristicsOperation conditions:Ta=-40to 125℃,VDD=3.0~5.5V unless otherwise noted.Symbol1Parameter Conditions/Notes Min.Typ.Max.Unit VDD Supply Voltage - 3.0 3.3~5.0 5.5V HVPP Supply Voltage - 6.757.07.25V Idd Supply Current -51015mA LSB Resolution (ABZ Mode)N Steps per Cycle -360°/N -°INL Integral Non-Linearity Note(1)-±0.75±1.5°DNL Differential Non-Linearity (ABZ Mode), Figure 3@1000 PPR-±0.01-°TN Transition Noise (ABZ Mode)25℃, HYST=4 Note(2)-0.01-°rms Hyst Hysteresis (ABZ Mode)HYST=0 Note(2)-0.022-°T PwrUp Power-Up Time VDD Ramp<10us-16-ms T DelayPropagation Delay-13usPWM Output Characteristics Conditions/Notes Min.Typ.Max.Unit FPWM PWM Frequency Programmable -971.1/485.6-Hz T Rise Rising Time C L =1nF --1us T FallFalling TimeC L =1nF--1usNote (1):The typical error value can be achieved at room temperature and with no off-axis misalignment error.The maximum error value can be achieved over operation temperature range,at maximum air gap and with worst-case off-axis misalignment error.Note (2):HYST could be set to:0=1LSB,1=2LSB,2=4LSB,3=8LSB,4=0LSB,5=0.25LSB,6=0.5LSB,7=1LSB.Here 1LSB=360°/214=0.022°.Digital I/O Characteristics(Push-Pull Type in Normal Mode)Symbol Parameter Conditions/Notes Min.Typ.Max.Unit V IH High Level Input Voltage-0.7*VDD--V V IL Low Level Input Voltage---0.3*VDD V V OH GPIO Output High Level Push-pull (Iout=2mA)VDD-0.25--V V OL GPIO Output Low Level Push-pull(Iout=2mA)--0.25VFigure 3: Drawing Illustration INL, DNL and TN (for 10 bit case)6. Magnetic Input SpecificationsOperation conditions:Ta=-40to 125℃,VDD=3.0~5.5V unless otherwise noted,two-pole cylindrical diametrically magnetized source.Symbol ParameterConditions/Notes Min.Typ.Max.UnitDmag Diameter of Magnet Recommended Magnet: Ø10mm x 2.5mm for Cylindrical Magnets -10-mmTmag Thickness of Magnet -- 2.5-mm Bpk Magnetic Input Field Amplitude Measure at the IC Surface 30-1,000mT AG Air Gap Magnetic to IC Surface Distance- 2.0 3.0mm RSRotation Speed--25,000RPMDISPOff Axis MisalignmentMisalignment ErrorBetween Sensor Sensing Center and Magnet Axis (See Figure 4)--0.3mmTCmag1Recommended Magnet Material and Temperature Drift CoefficientNdFeB (Neodymium Iron Boron)--0.12-%/℃TCmag2SmCo (Samarium Cobalt)--0.035-Figure 4: Magnet ArrangementAir GapOff-axis MisalignmentN S7. Output ModeThe MT6816provides ABZ,UVW and PWM signals at output pins,and also 14-bit absolute angle position data could be transferred by SPI interface (Both 3-Wire and 4-Wire modes).7.1 I/O Pin ConfigurationPin#3-Wire SPI4-Wire SPIABZ+PWMUVW+PWM1CSN CSN VDD VDD 3PWM PWM PWM PWM 5SDAT MOSI A U 6-MISO B V 7SCKSCKZWI/O Pin Configuration For SOP-8package,ABZ,UVW,PWM and SPI Interface are configured as below table.Figure 5: ABZ, UVW and PWM Output Reference Circuit w/o MTP Programming7.2 Reference Circuit for ABZ, UVW and PWM ModeFigure 6: ABZ, UVW and PWM Output Reference Circuit w/i MTP Programming12348765A/UB/V Z/W VDDTVS(6V)0.1ufPWM NC12348765A/UB/V Z/W VDDTVS(6V)0.1ufPWM HVPP1uf NC7.3 Quadrature A,B and Zero-Position Output (ABZ Mode)As shown in Figure 7,when the magnet rotates counter-clock-wise (CCW),output B leads output A by 1/4cycle,when the magnet rotates clock-wise (CW),output A leads output B by 1/4cycle (or 1LSB).Output Z indicates the zero position of the magnet.After chip power-on,the ABZ output is blocked for 16ms to guarantee proper output.Figure 7: ABZ output with VDD power onAZCCWB360°VDDCW16msOutput Z indicates the zero position of the magnet and the pulse width of Z is selectable as 1,2,4,8,12,16LSBs and 180°as shown in Figure 8and Figure 9.It is guaranteed that one Z pulse is generated for every rotation.The zero position is user programmable。

“电磁学”英汉对照专业词汇

第一章electric field 电场（强度）electric potential 电势potential difference 电势差charge 电荷volume charge density 体电荷密度term 术语find 求uniformly distribute 均匀分布located at 位于circular arc 圆弧semicircle 半圆radius 半径magnitude 大小，数量direction 方向conducting 导电的spherical shell 球壳positive 正negative 负value 值grounded sphere 接地球vacuum 真空electrostatic potential 静电势第二章 / 第三章spherical capacitor 球形电容器concentric spherical shells 同心球壳capacitance 电容量reduce 简化parallel-plate capacitor 平板电容器dielectrics 电介质area 面积separation 间隔，间距battery 电池disconnected 断开连接slab 厚板thickness 厚度dielectric constant 介电常数，电容率calculate 计算energy 能量neglect 忽略ignore 忽略end effects 边缘效应edge effects 边缘效应surface charge density 面电荷密度interface 分界面cylindrical capacitor 圆柱形电容器nonconducting material 非导电材料force 力fringing fields 边缘场第四章Current 电流steady current 稳恒电流current density 电流密度resistor 电阻器resistance 电阻resistivity 电阻率conductivity 电导率wire 电线assume 假定，设想truncated 切去顶端的right-circular cone 正圆锥altitude 高度length 长度taper 锥度，坡度cross section 横截面special case 特殊情况closed circuit 闭合电路magnetic dipole moment 磁偶极矩mass 质量lead 导线，铅第五章 / 第六章magnetic field 磁场tension 张力rectangular loop 矩形回路N close-packed turns N密绕匝coil of n turns n 匝线圈rotate 旋转long straight wire 长直导线copper rod 铜棒horizontal rails 水平轨道coefficient of static friction 静摩擦系数vertical 竖直，垂直slide 滑动switch 电键，开关function 函数，功能coaxial cable 同轴电缆cylinder 圆柱体per unit length 单位长度self-inductance 自感mutual inductance 互感diameter 直径perpendicular to 垂直于angular velocity 角速度externally applied torque 外加力矩maintain 保持rotation 旋转transient effects 暂态效应axis 轴beam of particles 粒子束momentum 动量impinge on 撞击focus to 聚焦于approximation 近似scatter 散射focal length 焦距第八章Power 功率Cycle 周期Qualitatively 定量地Semi-infinite 半无限electrical network 电路网络inductance 感应terminal 终端alternating voltage 交流电压winding 绕组transformer 变压器第九章Circular 圆形的Voltage 电压Retardation 延迟Maxwell’s equations 麦克斯韦方程组Symmetry 对称region 区域discontinuity 不连续surface current 面电流emit 发射pulse 脉冲frequency 频率dispersion 扩散interstellar medium 星际介质measure 测量distance 距离hint 暗示response 响应。

电磁场词汇汉英对照表

电磁场微波词汇汉英对照表二端口网络two port network二重傅立叶级数double Fourier series入射场incident field入射波incident wave小波wavelet无功功率reactive power无限（界）区域unbound region无源网络passive network互易性reciprocity互阻抗mutual impedance互耦合mutual coupling互连interconnect天线antennas天线方向性图pattern of antenna匹配负载matched load孔aperture孔（缝）隙天线aperture antennas内阻抗internal impedance介电常数permittivity介质dielectric介质波导dielectric guide介质损耗dielectric loss介质损耗角dielectric loss angle介电常数dielectric constant反射reflection反射系数reflection coefficient分离变量法separation of variables五画主模dominant mode正交性orthogonality正弦的sinusoidal右手定则right hand rule平行板波导parallel plate waveguide平面波plane wave功率密度density of power功率流（通量）密度density of power flux布魯斯特角Brewster angle本征值eigen value本征函数eigen function边值问题boundary value problem四端口网络four terminal network矢量位vector potential电压voltage电压源voltage source电导率conductivity电流元current element电流密度electric current density电荷守恒定律law of conservation of charge 电荷密度electric charge density电容器capacitor电路尺寸circuit dimension电路元件circuit element电场强度electric field intensity电偶极子electric dipole电磁兼容electromagnetic compatibility 矢量vector矢径radius vector失真distortions平移translation击穿功率breakdown power节点node安培电流定律Ampere’s circuital law传播常数propagation constant亥姆霍兹方程Helmholtz equation动态场dynamic field共轭问题conjugate problem共面波导coplanar waveguide （CPW）有限区域finite region有源网络active network有耗介质lossy dielectric导纳率admittivity同轴线coaxial line全反射total reflection全透射total transmission各向同性物质isotropic matter各向异性nonisotropy行波traveling wave光纤optic fiber色散dispersion网格mesh全向天线omnidirectional antennas阵列arrays串扰cross-talk回波echo良导体good conductor均匀平面波uniform plane wave均匀传输线uniform transmission line近场near-field麦克斯韦方程Maxwell equation克希荷夫电流定律Kirchhoff’s current law环行器circulator贝塞尔函数Bessel function时谐time harmonic时延time delay位移电流electric displacement current 芯片chip芯片组chipset远场far-field变分法variational method定向耦合器directional coupler取向orientation法拉第感应定律Faraday’s law of induction 实部real part空间分量spatial components波导waveguide波导波长guide wave length波导相速度guide phase velocity波阻抗wave impedance波函数wave function波数wave number泊松方程Poisson’s equation拉普拉斯方程Laplace’s equation坡印亭矢量Poynting vector奇异性singularity阻抗矩阵impedance matrix表面电阻surface resistance表面阻抗surface impedance表面波surface wave直角坐标rectangular coordinate极化电流polarization current极点pole非均匀媒质inhomogeneous media非可逆器件nonreciprocal devices固有（本征）阻抗intrinsic impedance单位矢量unit vector单位法线unit normal单位切线unit tangent单极天线monopole antenna单模single mode环行器circulator驻波standing wave驻波比standing wave ratio直流偏置DC bias九画标量位scalar potential品质因子quality factor差分法difference method矩量法method of moment洛伦兹互易定理Lorentz reciprocity theorem屏蔽shield带状线stripline标量格林定理scalar Green’s theorem面积分surface integral相对磁导率relative permeability相位常数phase constant相移器phase shifter相速度phase velocity红外频谱infra-red frequency spectrum矩形波导rectangular waveguide柱面坐标cylindrical coordinates脉冲函数impulse function复介电常数complex permittivity复功率密度complex power density复磁导率complex permeability复矢量波动方程complex vector wave equation 贴片patch信号完整性signal integrity信道channel寄生效应parasite effect指向天线directional antennas喇叭天线horn antennas十画准静态quasi-static旁路电流shunt current高阶模high order mode高斯定律Gauss law格林函数Green’s function连续性方程equation of continuity耗散电流dissipative current耗散功率dissipative power偶极子dipole脊形波导ridge waveguide径向波导radial waveguide径向波radial wave径向模radial mode能量守恒conservation of energy能量储存energy storage能量密度power density衰减常数attenuation constant特性阻抗characteristic impedance特征值characteristic value特解particular solution勒让德多项式Legendre polynomial积分方程integral equation涂层coating谐振resonance谐振长度resonance length十一画混合模hybrid mode部分填充波导partially filled waveguide递推公式recurrence formula探针馈电probe feed接头junction基本单位fundamental unit理想介质perfect dielectric理想导体perfect conductor唯一性uniqueness虚部imaginary part透射波transmission wave透射系数transmission coefficient球形腔spherical cavity球面波spherical wave球面坐标spherical coordinate终端termination终端电压terminal voltage射频radio frequency探针probe十二画涡旋vortices散度方程divergence equation散射scattering散杂电容stray capacitance散射矩阵scattering matrix斯托克斯定理Stoke’s theorem斯涅尔折射定律Snell’s law of refraction阴影区shadow region超越方程transcendental equation超增益天线supergain antenna喇叭horn幅角argument最速下降法method of steepest descent趋肤效应skin effect趋肤深度skin depth微扰法perturbational method等相面equi-phase surface等幅面equi-amplitude surface等效原理equivalence principle短路板shorting plate短截线stub傅立叶级数Fourier series傅立叶变换Fourier transformation第一类贝塞耳函数Bessel function of the first kind第二类汉克尔函数Hankel function of the second kind 解析函数analytic function激励excitation集中参数元件lumped-element场方程field equation场源field source场量field quantity遥感remote sensing振荡器oscillators滤波器filter十三画隔离器isolator雷达反射截面radar cross section （RCS）损耗角loss angle感应电流induced current感应场induction field圆波导circular waveguide圆极化circularly polarized圆柱腔circular cavity铁磁性ferromagnetic铁氧体陶瓷ferrite ceramics传导电流conducting current传导损耗conduction loss传播常数propagation constant传播模式propagation mode传输线模式transmission line mode传输矩阵transmission matrix零点Zero静态场static field算子operator输入阻抗input impedance椭圆极化elliptically polarized微带microstrip微波microwave微波单片集成电路microwave monolithic integrated circuit MMIC毫米波单片集成电路millimeter wave monolithic integrated circuit M3IC十四画漏电电流leakage current渐进表示式asymptotic expression模式mode模式展开mode expansion模式函数mode模式图mode pattern截止波长cut off wavelength截止频率cut off frequency鞍点saddle频谱spectrum线性极化linearly polarized线积分line integral磁矢量位magnetic vector potential磁通magnetic flux磁场强度magnetic intensity磁矩magnetic moment磁损耗角magnetic loss angle磁滞损耗magnetic hysteresis磁导率permeability十五画辐射radiate增益gain横电场transverse electric field横电磁波transverse electromagnetic wave劈wedge十六画雕落场evanescent field雕落模式evanescent mode霍尔效应Hall effect辐射电阻radiation resistance辐射电导radiation conductance辐射功率radiation power辐射方向性图radiation pattern谱域方法spectral method十七画以上瞬时量insaneous quantity镜像image峰值peak value函数delta function注：本词汇表参考了《正弦电磁场》（哈林顿著孟侃译）。

一磁场(magnetic field)

2π r
I B
I
X
B
半无限长载流长直导线的磁场半无限长载流长直导线的磁场
π θ1 → 2 θ 2 →π
青岛科技大学
BP =
µ0I
4π r
I
o
r
* P
大学物理讲义
例2 圆形载流导线的磁场. 圆形载流导线的磁场真空中 , 半径为R 的载流导线 , 通有电流I , 称圆电流. 的磁感强度的方向和大小. 电流求其轴线上一点 p 的磁感强度的方向和大小
大学物理讲义
z
青岛科技大学
带电粒子在磁场中沿 v 其他方向运动时 F 垂直 v 于 v 与特定直线所组成的平面. 的平面当带电粒子在磁场中垂直于此特定直线运动时受力最大. 受力最大 v v v
Fmax qv
v v v 将大小与 q , v 无关时，受力 Fmax ,将vFmax × v 方
3、7点：dB 、点 +3
+
7
v Idl
R
6 5
青岛科技大学
=
µ 0 Id l
4π R
2
2、4、6、8 点：、、、
+4
dB =
µ 0 Idl
4π R
sin 450 2
大学物理讲义
四
毕奥---萨伐尔定律应用举例毕奥萨伐尔定律应用举例萨伐尔定律载流长直导线的磁场. 例1 载流长直导线的磁场
B
π β1 = , β 2 = 0 2 1 B = µ 0 nI 2
µ0nI
x
大学物理讲义
1 µ 0 nI 2
O青岛科技大学z源自v Idlv' r
o
R
θ

大学英文版电磁学讲义1-9

9.2 Magnetization and Bound Currents 磁化和束缚电流
The volume density of bound current(束缚电流体密度): J x =∇ ×M x . The surface density of bound current(束缚电流面密度): K b x = M x × n . (9.13) (9.12)
J by =−∂ M z /∂ x .
. => J b =∇× M For M = M k Fig. 9.8.
K =M × n M= n m k
increasing in the Fig. 9.9 M z x k +x direction. The bound current is ∂M z J b =∇ × M=− j ∂x
9.4 Problems Involving Free Currents and Magnetic Materials 包含自由电流和磁介质的问题
Using Ampere's law of H, we can solve some problems in magnetic material with symmetry. Example 5: An infinite slab of a conducting material(无穷大导体平板) with magnetic susceptibility m carries a certain current distribution. The slab is parallel to the x y plane, between z = −a and z = a. It carries a free i . Above the x y plane the current volume current density J f z = J 0 z / a is out of the page, below it is into the page.

一磁场magnetic field

毕奥---萨伐尔定律应用举例
青岛科技大学大学物理讲义
0 I B 4 r0

2
1
. B 的方向沿 x 轴的负方向电流 I 的指向与磁场 B 的方
向形成右手螺旋关系。
0 I sin d i （cos 2 cos 1 ） i 4 r0
z
D
2
无限长载流长直导线的磁场.
青岛科技大学大学物理讲义
1）若线圈有 N 匝
（ 1） I （2 ）
R B x 0 I 0 o B0 2R
I
（ 4）
0 I BA 4π d
d *A
R1 R2
R
o （ 3） I R
B0
0 I
4R
（ 5） I
*o
B0
o
0 I
8R
B0
0 I
4 R2

0 I
4 R1

大学物理讲义
y R cos z R sin
青岛科技大学
r xi R cos j sin k dl R sin j cos k 0 IR dB sin j cos k 3 4 r xi R cos j sin k d 0 IR Ri x cos j x sin k d 3 4 r 2 0 IR 线圈电流 I 的指向与磁场 B 的方 B i 3 向形成右手螺旋关系。 2 2 2 2 （x R ）
7 2 真空磁导率0 4π 10 N A
r
(magnetic permeability)
任意载流导线在点 P 处的磁感强度
磁感强度叠加原理

17-1基础物理学讲义Magnetic Field

magnetic field along the axis
of a rotating charged disc
with surface density .
Solution: Divide the disc into
d
many rings as show in the figure. The electric current on a
Bz
dBz
0
R 0
3d (z2 2)3
2
0
2z2 R2
(
z
2
R2
)1
2
2
z
.
Example 17.6 Suppose the earth’s magnetic field is produced by a current circling around underneath the equator at an average distance of 5000km from the center. What would be the value of it if the field at either pole is about 10-4T(1 gauss).
( sin
)d .
The resultant field can be obtained by integrating
from one end of the solenoid to the other, i. e. ,
Bz
μ 0nI 2
2
sin d
1
μ 0nI 2
(cos2
cos1).
For an infinite solenoid, 1 and 2 0 respectively. The result is Bz 0nI.

210978225_不同表面基团的纤维素纳米晶体薄膜在不同磁场下的光学特性响应

王天卉，卢舒瑜，周宇星，等. 不同表面基团的纤维素纳米晶体薄膜在不同磁场下的光学特性响应[J]. 食品工业科技，2023，44（7）：226−233. doi: 10.13386/j.issn1002-0306.-2022060021WANG Tianhui, LU Shuyu, ZHOU Yuxing, et al. Effect of Magnetic Field on Optical Properties of CNC Films with Different Surface Groups[J]. Science and Technology of Food Industry, 2023, 44(7): 226−233. (in Chinese with English abstract). doi:10.13386/j.issn1002-0306.-2022060021· 包装与机械 ·不同表面基团的纤维素纳米晶体薄膜在不同磁场下的光学特性响应王天卉1,2,3，卢舒瑜1,2,3，周宇星1,2,3，马　涛1,2,3, *，宋　弋1,2,3（1.中国农业大学食品科学与营养工程学院，北京 100083；2.农业农村部果蔬加工重点实验室，北京 100083；3.国家果蔬加工工程技术研究中心，北京 100083）摘　要：本文探究了磁场对不同表面基团的纤维素纳米晶体（Cellulose Nanocrystal ，CNC ）薄膜光学特性的影响。

以硫酸化纤维素纳米晶体（S-CNC ）为原料，通过2,2,6,6-四甲基哌啶-1-氧基自由基（TEMPO ）氧化制备表面带有羧基的纳米纤维素（T-CNC ），并采用傅里叶红外光谱、扫描电子显微镜和Zeta 电位对其基本结构进行表征。

并在无磁场、垂直磁场、倾斜磁场、水平磁场四种模式下观察磁场对不同表面电荷CNC 薄膜的影响。

结果表明，T-CNC 表面带有羧基，S-CNC 表面带有硫酸酯基。

英语偏旁部首(词根词缀)范文

英语中的偏旁部首词根词缀就相当于英文单词的偏旁部首，单词都是由字母组合而成的，所以你记忆单词的时候要懂得把它按照词根词缀分开。

就像我们记忆汉字的时候，是按照偏旁部首进行的，记英文单词也可以有类似的办法，就是用词根词缀记单词。

只要掌握好词根词缀所代表的相应含义，．就可以方便轻松的记住单词。

希望大家在学习词根词缀的过程当中，尽量通过老单词来学习认识词缀，然后再用词缀学习新的词汇，用已知来助词未知.如：①Representative。

re在英语里是一个偏旁部首，它是“回来”的意思；pre也是一个偏旁部首，是“向前”的意思；sent也是一个偏旁部首，是“发出去、派出去”的意思；a仅是偏旁部首之间的一个“连接件”，没了它两个辅音字母t就要连在一起了，发音会分不开，会费劲，因此用一个元音字母a隔开一下；tive也是一个偏旁部首，是“人”的意思。

所以re-pre-sent-a-tive，就是“回来-向前-派出去-的人”，即“回来征求大家的意见后又被派出去替大家讲话的人”，这不就是“代表”的意思吗！这么去认识一个单词才是真正“认识”了这个单词，把它认识到了骨子里。

②psychology。

psy=sci，是一个偏旁部首，是“知道”的意思；cho是一个偏旁部首，是“心”的意思；lo是一个偏旁部首，是“说”的意思；gy是一个偏旁部首，是“学”的意思，logy合起来是“学说”的意思。

因此psy-cho-logy连起来就是“知道心的学说”，因此就是“心理学”的意思。

依此类推，不多举例了，所要表达的观点已经清楚了，那就是，不要去死记硬背单词的汉语意思，而要用识别“偏旁部首”的方法去真正认识一个单词，真正认识了单词后，你会发现单词表里的汉语翻译原来其实很勉强，有时甚至根本翻译不出来，因为汉语和英语是两种不同的文字体系，两者在文字上本来就不是一一对应的，只背英语单词的汉字意思是不能真正认识这个单词的，会造成很多的后续学习困难，会造成你一辈子看英语单词如雾里看花，永远有退不掉的陌生感。

MAGNETICRESONANCEIMAGING(MRI)BASICS磁共振成像MRI基础

preceding increased blood flow – Working on imaging other substances
Subtractive Logic
• Most of the brain is active during most events
• Try to isolate regions that are specific to some aspect of the event of interest
• As nuclei settle back into alignment with fixed field, they emit measurable EM energy themselves
– Variations in how long it takes the nuclei to de-phase & to settle back to original wobble in fixed field
MRI Magnetic Fields Cont’d
• After a few seconds in a magnetic field, the spin axes of a small fraction of the relevant nuclei align with each other
– = Axes all wobble in same way – Strength of the magnetic field determines how big the fraction is – Spin axes are aligned, but not precessing in phase at this point – Alignment of spin axis of nuclei causes the whole magnetic field

电磁感应-电磁场英文名词

附录
6
物理学
第五版
物理学
第五版
磁化曲线磁滞磁滞回线磁滯损耗剩磁退磁
物理学名词中英文对照
magnetization curve hysteresis hysteresis loop hysteresis loss remanent magnetization demagnetization
第五版
物理学
第五版
物理学名词中英文对照
电磁阻尼自感自感电动势自感系数互感互感电动势互感系数
electromagnetic damping self-inductance self-induced emf self-induced coefficient mutual inductance emf of mutual induction mutual induction coefficient
附录
7
物理学
第五版
物理学
第五版
铁磁质磁场强度
相对磁导率传导电流磁化电流磁畴
物理学名词中英文对照
ferromagnetic material magnetic field intensity Relative permeability conduction current magnetization current magnetic domain
物理学
第五版
楞次楞次定律动生电动势
感生电动势
有旋电场涡流
物理学名词中英文对照
Lenz Lenz law motional electromotive force induced electromotive force curl electric field eddy current

航海及海运专业英语词汇(M1)

航海及海运专业英语词汇(M1)航海及海运专业英语词汇(M1)航海及海运专业英语词汇(M1)m-curve m曲线m-station 主台m-tooth m形锯齿m-type single-pull hatchcover 斜置型舱口盖macadam 碎石macaroni 通心粉macassar oil 马卡沙油mace 豆寇肉macglashan tank 边水柜mach angle 马赫角mach number 马赫数mach shock 马赫波mach wave 马赫波mach 马赫mach 马赫数machi 镇machicolated form 凹凸形machinability rating 可加工性指数machinability 可加工性machinable 可加工的machinable 可以机械加工的machine assembly 机器装配machine attendance 机器保养machine attention 机器保养machine available time 机器可用时间machine base 机器底座machine building 机器制造machine building 机器制造业machine casting 机器铸造machine casting 机器铸造机器铸件machine check interrupt 机器校验中断machine check interruption 机器检查中断machine check 自动校核machine code programming 手编程序machine code 机器代码;指令码machine code 机器代码指令码machine component 机器零件machine construction 机器构造machine cover 机器护罩machine cut 机床切削machine cutting tool 机床切削工具machine cycle 机器工作周期machine design 机器设计machine drawing 机械图machine drawing 机械图机械制图machine drill 钻床机用钻头machine driven switching system 机动制自动电话交换机machine efficiency 机器效率machine element 机件machine element 机器零件machine element 机械零件machine error 机器误差machine factory 机器厂machine fault 机器故障machine finish allowance 机械加工留量machine finish 机械精加工machine finishing 机械精加工machine finshing 机械精加工machine foundation 机器底座machine frame 机架machine hand 机械手machine handle 机器手柄machine house 机器房machine instruction 机器说明书machine language 机器语言machine language 计算机语言machine maintenance 机器保养machine maintenance 机器维护machine member 机器零件machine molding 机械造型machine net weight 机器净重machine of normal series 标准型机器machine oil 机油machine operation 机器操作machine oriented language 面向机器语言machine parts 机器零件machine pin 机用销machine plant 机器厂machine press-packing 机器打包machine program control 机器程序控制machine program control 机器程序控制机床程序控制machine program 机器程序machine repair shop 机修车间machine riveting 机铆machine riveting 机器铆接machine riveting 机器铆接;机械紧固machine riveting 机械紧固machine riveting 机械铆接machine room 机舱machine saw 机锯machine series 机器系列machine shop 机械车间machine space zero people 无人机舱machine specification 机器说明书machine spoiled time 机器故障时间machine switched off 机器关闭machine switching telephone system 机动制自动电话machine telegraph 车钟machine tool 机床machine unit 运算装置machine up 机械加工machine upkeep 机器保养machine vice 机床虎钳machine washing 机械洗舱machine welding 机械焊接machine welding 机械化焊接machine welding 自动焊machine winding 电机绕组machine word 计算机字machine work 机械加工machine works 机械厂machine workshop 机械车间machine 机器machine 机器机床机械machine-dependent 与机器有关的machine-hour 一台机器在一小时内的工作量machine-independent 与机器无关的machine-language coding 机器语言编码machine-made 机制的machine-made 机制的机械的machine-oriented language 面向机器语言machine-readable 机器可读的machine-sensible 机器可读的machineacoustic efficiency 机声效率machined surface 机械加工面machined-spoiled time 机器浪费时间machinemolding 机械造型machinery afterward 尾机machinery -aft ship 尾机舱船machinery -aft 尾机舱machinery aft ship 尾机舱船machinery aft 尾机舱machinery aft 尾机型船machinery alarm system 机舱警报系统machinery and boilers are classed by british standard 按英国标准定级的机械和锅炉;按英国标准定级的机械设备和锅炉machinery arrangement 机舱布置machinery arrangement 机舱设备布置machinery bed 机器底座machinery bilge 机舱舱底machinery breakdown insurance 机器损坏保险machinery breakdown 机器故障machinery bronze 机用青铜machinery bulkhead 机舱舱壁machinery casing 机舱棚machinery casulty control 机械设备损害管制machinery certificate 机器证书机械设备合格证书machinery certificate 机械设备合格证书machinery charge qualification 机械负荷合格证机械负荷合格证明machinery charge qualification 机械负荷合格证明machinery charge qualification 机械负荷合格证明机械负荷合格证machinery chock 机器防震木垫块machinery class notation 轮机标志machinery class notion 机械装置入级标志machinery class 劳埃德船级社机械设备级别证书machinery classfication and inspection record 船机入级记录和检验报告machinery classification certificate 轮机入级证书machinery classification certificate 机械设备入级证书machinery classification certificate 轮机入级证书machinery compartment 机舱machinery control and surveillance 机舱控制与监视machinery control center 机舱集控中心machinery control compartment 机舱操纵室machinery control console 船机控制台machinery control console 机械控制台machinery control console 机械控制台船机控制台machinery control room 机舱控制machinery controls 机械控制装置machinery damage 机器损坏machinery data-logging installation 机械设备数据自动记录装置machinery drainage system 机舱泄水系统machinery efficiency 机器效率machinery efficiency 机械效率machinery fitted aft 尾机machinery fitting 机械设备安装machinery forward 机舱在船首machinery foundations 机械设备底座machinery horse-power 机器马力machinery in ns class 具有推进动力的ns级符号machinery index 机械目录machinery installation 机械装置machinery items 机械零件machinery layout 机械设备布置machinery layout 机械设备布置图machinery monitoring system 机器监控系统machinery monitoring system 机器监视系统machinery nippon standard 日本一级机动船级machinery noise 机器噪声machinery noise 机械噪声machinery number 主机数machinery number 主机特征数machinery numeral 主机数machinery numeral 主机特征数machinery performance monitoring 机械工况监测machinery place zero people 无人机舱machinery plant 机械装置machinery remote monitoring 机舱遥控监视machinery repairman 机械修配工machinery room arrangement 机舱布置machinery room 机舱machinery space boundary 机器处所限界面machinery space bulkhead 机舱壁machinery space bulkhead 机舱壁;机器处所舱壁machinery space bulkhead 机械处所舱壁machinery space discharge 机器处所排放machinery space of category a a 类机器处所machinery space ventilation 机舱通风machinery space zero ship 无人机舱船machinery space 机舱machinery space 机舱;机器处所machinery specification 机器说明书machinery specification 机械设备说明书machinery surveillance system 机舱监视系统machinery survey 机器检查machinery survey 机器检验machinery survey 机器检验机械检验machinery surveyed 机器检验完毕machinery trial 机器试车machinery trial 机器试车主机试车machinery ventilation 机舱通风machinery vibration analysis 机械振动分析machinery weight 机器重量machinery wieght 机器重量机械设备重量machinery 机器machinery 机械machinery 机械装置machinery 机械装置;机器;机械machinery 联合装置machinery-aft ship 尾机舱船machinery-aft 尾机舱machinery-unmanned 无人机舱machinerybulkhead 机舱舱壁machining accuracy 机械加工精度machining allowance 机械加工余量machining dimension 机械加工尺寸machining drawing 机械加工图纸machining of metals 金属切削加工machining symbol 机械加工符号machining time 机械加工时间machining 机械加工machinist 机工machinist 技工machmeter m表machmeter 马赫数表mack bridge 烟囱桅瞭望台mack bridge 烟囱桅了望台mack 烟囱桅mackerel sky 鱼鳞天mackerel breeze 鲭风mackerel gale 同上mackerel gale 鲭风mackerel pocket 鲐鱼舷张网mackerelsky 鱼鳞天mackintosh 轻而薄的防水织物macomb strainer 泄水总管上的网状过滤器macrame work 水手编织法的一种macro etched for examination 宏观浸蚀检查macro examination 宏观检查macro modular computer 宏模组件计算机macro 长macro- 表示宏观的macro-algae 大藻类macro-corrosion 大量腐蚀macro-crack 宏观缝macro-molecule 大分子macro-molecule=macromolecule 大分子macroalgae 、硬壳虫macroclimate 大气候macrocode 宏代码macrocoding 宏编码macrocontract 总合同macrofouler 大型污底生物macrofouler 大型污底生物(包括贻贝macrographic examination 宏观检验macrography 宏观检查macrography 宏观图macromolecular 大分子macromolecule 大分子macroquake 大地震macroscopic test 宏观检查macroscopic test 肉眼检查macroscopic 宏观的macroscopic 肉眼可见的macrostructure 宏观结构mactaggart telemotor 遥控电动传动装置maculosus 斑状madder root 茜根made block 组合滑车made eye 绕匝索环made eye 绕匝索环绕匝索环made good course 直航航路made in china 中国制造的made keelblock 组合龙骨墩made mast 组合桅made merchantable 可销售made merchantable 可销售使成商品made 制的made 制造的made 制造的制成的made-to-order 定制的made-up 人工的madrepore 石蚕madrepore 石蚕石珊瑚石珊瑚底madrepore 石珊瑚mae nam 河mae nam 河河mae vest 气胀式救生衣大三角帆maelstrom 大旋涡maestro 亚得里亚海夏天的一种西北风mag-dynamo 永磁发电机高压永磁发电机直流发电机组mag-dyno 永磁发电机高压永磁发电机直流发电机组magamp 磁性放大器magazine cock 火药舱船底塞magazine screen 火药舱防闪帆布帘magazine tool holder 库房工具架magazine 库房magazine 杂志;箱;仓库;弹药库magazine 杂志库房magazine 杂志库房料斗胶卷盒magazing 火药库magdynamo 永磁发电机高压永磁发电机直流发电机组magellan jacket 厚羊毛值班大衣magellanic clouds 麦哲伦云magic eye 电眼magic eye 电眼光调谐指示管光调谐指示器magic eye 电眼光调谐指示器magic hand 机械手magic lantern 幻灯magic t t型波导支路;混合接头magic t t型波导支路混合接头magmeter 直读式频率计magnaflux inspection 磁力检验magnaflux inspection 磁力探伤magnaflux inspection 磁力探伤检查magnaflux method 磁力线法magnaflux powder 磁力探伤用铁粉magnaflux powder 磁性探伤用铁粉magnaflux test 磁力探伤magnaflux test 磁力探伤检查magnaflux 磁力探伤法magnaflux 磁通量磁力探伤法magnaflux 电磁探测法magnafluxinspection 磁力检验magnalium 镁铝合金magnasil 镁氧水泥甲板敷料magnavox 美国米罗华公司magnesia brick 镁砖magnesia dead-burned 重烧镁magnesia unslacked 轻烧镁magnesia 氧化镁magnesite clinker 重烧镁magnesite 菱镁矿magnesite 菱镁矿;镁氧水泥甲板敷料magnesite 菱镁矿镁氧水泥甲板敷料magnesium alloy 镁合金magnesium carbonate 碳酸镁magnesium chloride 氯化镁magnesium hydroxide 氢氧化镁magnesium oxide slurry inhibitor 氧化镁悬浮状抑制剂magnesium phosphate 磷酸镁magnesium sulphate 硫酸镁magnesium 镁magnesium alloy 镁合金magnesium anode 镁阳极magnesium carbonate 碳酸镁magnesium chloride 氯化镁magnesium flat cell 镁扁平型电池magnesium hydroxide 氢氧化镁magnesium nitrate 硝酸镁magnesium oxide slurry inhibitor 氧化镁悬浮状抑制剂magnesium sulphate 硫酸镁magnesium 镁magnesiumalloy 镁合金magnesiumcarbonate 碳酸镁magnesiumchloride 氯化镁magnesiumhydroxide 氢氧化镁magnesiumoxide slurry inhibitor 氧化镁悬浮状抑制剂magnesiumphosphate 磷酸镁magnesiumsulphate 硫酸镁magnesyn compass 远距离指示磁罗经magnesyn repeater 磁罗经复示器magnesyn 磁电式自动同步机magnesyn 永磁自动同步机magnesyn 永磁自整角机magnet band 磁带magnet call telephone exchange 磁石式电话交换机magnet carrier 带磁体magnet catch 电磁制动器magnet chamber 磁铁柜magnet coil 电磁铁线圈magnet core 磁心magnet crane 磁力起重机magnet crane 电磁吸盘式起重机magnet electric display instrument 磁电式显示仪表magnet housing 磁铁壳magnet meter 磁通计magnet pole 磁极magnet reed switch 磁性舌簧开关magnet separator 磁力分离器magnet steel 磁钢magnet stopper 电磁制动器magnet valve 电磁阀magnet wire 磁线magnet 磁石magnet 磁体magnet 磁铁magnet 控制磁铁调向磁铁magnetic pilot 磁罗经自动操舵magnetic strength 磁场强度magnetic -core memory 磁心存储器magnetic -core switch 磁心开关magnetic -coupling flowmeter 磁耦合式流量表magnetic -field pattern 磁场特性magnetic -film memory 磁膜存储器magnetic -mechanical 磁-机械的magnetic -synchro 磁同步的magnetic abatement 消磁magnetic abnormal detection 地磁异常探测magnetic action 磁力作用magnetic adhesion 磁吸附magnetic aging 磁老化magnetic alloy 磁性合金magnetic amplifier 磁放大器magnetic amplifier 磁放大器磁性放大器magnetic amplifier 磁性放大器magnetic analysis 磁分析法magnetic anisotropy 磁各向异性magnetic annealing effect 磁致冷却效应magnetic annual change 地磁年变量magnetic anomaly detection 磁性异常探测magnetic anomaly 地磁异常magnetic athwartships deviation 横向磁场航向差magnetic attraction 磁吸引magnetic attraction 磁吸引力magnetic auto-steering gear 磁性自动操舵装置magnetic autosteering gear 磁性自动操舵装置magnetic axis 磁轴magnetic azimuth 磁方位magnetic azimuth 磁方位磁方位磁方位角magnetic azimuth 磁方位角magnetic balance type 磁性平衡式magnetic bar 磁棒magnetic bearing 磁方位magnetic bearing 磁方位磁方位magnetic bias 磁偏magnetic biasing 磁偏magnetic blow-out circuit breaker 磁吹断路器磁性灭弧断路器magnetic blow-out circuit breaker 磁吹灭弧断路器magnetic blow-out circuit breaker 磁吹灭弧断路器磁吹断路器磁性灭弧断路器magnetic blow-out 磁性灭弧magnetic body 磁体magnetic brake 磁力制动器magnetic brake 磁闸magnetic bridge 导磁率电桥magnetic bubble device 磁泡器件magnetic bubble memory 磁泡存储器magnetic bubble 磁泡magnetic card unit 磁卡片机magnetic cartridge recorder 磁带记录器magnetic cartridge 电磁式拾音头magnetic character figure 地磁特性图magnetic characteristic 磁特性magnetic charge 磁荷magnetic chart 地磁图magnetic chart 电磁图magnetic chuck 电磁吸盘magnetic circuit 磁路magnetic clutch 磁离合器magnetic clutch 电磁离合器magnetic clutch 电磁离合器磁离合器magnetic cluth 磁性离合器magnetic coefficient 磁化系数magnetic coefficient 磁化系数自差系数magnetic coefficient 自差系数magnetic compass pilot 磁罗经导航magnetic compass pilot 磁罗经驾驶仪magnetic compass pilot 磁罗经驾驶仪磁罗经导航磁罗经自动舵magnetic compass pilot 磁罗经自动舵magnetic compass table 磁罗经自差表magnetic compass table 磁罗经自差表磁罗经)自差表magnetic compass table 自差表magnetic compass 磁罗经magnetic compensator 磁补偿器magnetic compensator 磁性补偿器magnetic compensator 校正磁铁magnetic conductance 磁导magnetic conductivity 导磁率magnetic contactor 磁接触器magnetic contactor 磁接触器磁接触器magnetic control relay 磁控继电器magnetic controller 磁控制器magnetic core memory 铁心存储器magnetic core 磁心magnetic coupling 磁耦合magnetic coupling 电磁联轴节magnetic coupling 电磁联轴器磁耦合magnetic course 磁航向magnetic course 磁航向磁航向magnetic crack detection 磁力探伤magnetic crane 电磁吸盘式起重机magnetic crotchet 磁鼻magnetic damper 磁性阻尼器magnetic damping 磁性阻尼magnetic damping 磁阻尼magnetic declination 磁差magnetic declination 磁差;地磁变化magnetic declination 磁偏magnetic deflection 磁偏转magnetic deflection 磁致偏转magnetic deformation 磁性变形magnetic degree 磁角度magnetic delay-line 磁延迟线magnetic detection monitor 磁性探测监视器magnetic detection 磁性探测magnetic detection 磁性探伤magnetic detector 磁性检波器magnetic detector 磁性检波器磁性探伤仪magnetic deviation 磁差magnetic deviation 自差magnetic dial gauge 磁性指示表magnetic dip pole 磁极magnetic dip 磁倾角magnetic dipole 磁偶极子magnetic direction 磁航向magnetic disc head 磁盘磁头magnetic disc memory 磁盘存储器magnetic disc 磁盘magnetic disk memory 磁盘存储器magnetic dispersion 磁漏magnetic displacement 磁移magnetic distrubance 磁扰magnetic disturbance 磁扰magnetic domain 磁畴magnetic double coil 双铁芯线圈magnetic drag-type tachometer 磁感应式转速表magnetic drill press 电磁钻床magnetic drive 磁力传动magnetic drive 磁力传动带电磁离合器的传动装置magnetic drum memory capacity 磁鼓存储容量magnetic drum memory 磁鼓存储器magnetic drum receiving equipment 磁鼓接收设备magnetic drum recorder 磁鼓记录器magnetic drum storage 磁鼓存储器magnetic drum 磁鼓magnetic element for lubricating oil filter 润滑油滤器磁性元件magnetic element 磁性元件magnetic elements 地磁要素magnetic energy 磁能magnetic equator 无倾线magnetic fatigue 磁力疲劳magnetic fault detection 磁粉探伤magnetic feedthrough 通过外壳的磁场传动magnetic field coil 磁场线圈magnetic field intensity 磁场强度magnetic field 磁场magnetic film memory 磁膜存储器magnetic film 磁膜magnetic filter 磁性滤器magnetic flaw detecting 磁力探伤magnetic flaw detector 磁力探伤器magnetic flaw detector 磁力探伤仪magnetic float 磁性浮子magnetic floating valve 磁性浮子阀magnetic floating valve 电磁浮子阀magnetic flow meter 磁力式流量计magnetic flow 磁通量magnetic flux density 磁通密度magnetic flux linkage 磁链magnetic flux 磁通量magnetic flux 磁通量磁性熔剂磁性焊剂magnetic flux-density 磁通密度magnetic focusing 磁聚焦magnetic force 磁力magnetic friction clutch 磁性摩擦离合器magnetic gap 磁隙magnetic gate 磁门magnetic gear 磁力离合器magnetic gearing 电磁离合器magnetic head positioning construction 磁头定位机构magnetic head 磁头magnetic heading 磁船首向magnetic heading 磁航向magnetic heading 磁航向磁船首向magnetic holding device 电磁夹具magnetic hum 交流哼声magnetic hydraulic clutch 磁性液压离合器magnetic hysteresis loop 磁滞环线magnetic hysteresis 磁带magnetic hysteresis 磁滞magnetic ignition 磁石发电机点火magnetic inclination 磁偏角magnetic inclination 磁偏角磁力线偏转magnetic inclination 磁倾角magnetic induction density 磁感应强度magnetic induction flowmeter 磁感应式流量表magnetic induction gyroscope 磁感陀螺magnetic induction nuclear gyroscope 磁感应核陀螺magnetic induction 磁感应magnetic inductive capacity 磁感应能力magnetic inductive capacity 导磁率magnetic inductivity 导磁率magnetic ink character reader 磁墨水字符读出器magnetic inspection 磁力检查magnetic inspection 磁力探伤magnetic intensity 磁场强度magnetic intensity 磁强magnetic interference 磁场干扰magnetic interfering field 干扰磁场magnetic iron ore 磁铁矿石magnetic iron 磁铁magnetic lag 磁滞magnetic latitude 磁纬度magnetic leakage 磁漏magnetic levitation 用磁性飘浮空中magnetic lifting beam 电磁吸吊装置magnetic line of force 磁力线magnetic line 磁力线magnetic lines of force 磁力线magnetic linkage 磁链magnetic longitudinal deviation 纵向磁场航向差magnetic loop 磁性探测指示环magnetic loudspeaker 电磁式扬声器magnetic lubricating oil filter 润滑油磁性滤器magnetic magnetic s 磁学磁性元件magnetic map 地磁图magnetic material 磁性材料magnetic measurement 磁测量magnetic medium 磁介质magnetic meridian 磁子午线magnetic metal 磁性金属magnetic micrometer 磁性测微计magnetic mine 磁性水雷magnetic modulator 磁调制器magnetic moment 磁矩magnetic motive force 磁动力magnetic motive force 磁动势magnetic motive force 磁动势磁动力magnetic needle 磁针magnetic neutral line 磁中性线magnetic noise 磁力噪声magnetic north 磁北magnetic observation 磁力观测magnetic oil filter 磁性滤油器magnetic oil filter 磁性油滤器magnetic oil strainer 磁性滤油器magnetic oil strainer 磁性油滤器magnetic operational amplifier 磁运算放大器magnetic orientation 定磁方位magnetic parallel 等磁倾线magnetic parallel 等磁倾线等倾线的magnetic particle test 磁粉试验magnetic path 磁路magnetic permeability 导磁率magnetic permeance 磁导magnetic perturbation 磁扰动magnetic pick-up 电磁起吊器magnetic pick-up 电磁起吊器电磁式拾音器magnetic pickup 电磁起吊器magnetic pilot 磁罗经自动操舵magnetic plated wire memory 磁镀线存储器magnetic polarity 磁极性magnetic polarization 磁极化magnetic polarization 磁极化强度magnetic pole intensity 磁极化强度magnetic pole intensity 磁极强度magnetic pole 磁极magnetic potential difference 磁势位magnetic potential 磁势magnetic powder testing 磁粉检验magnetic prime vertical 磁东西圈magnetic properties 磁性magnetic pull 磁引力magnetic push-pull amplifier 磁力推挽式放大器magnetic range 校罗经叠标magnetic readwrite head 读写磁头magnetic record 磁带记录magnetic recorder 磁录音机magnetic recording head 磁头magnetic recording medium 磁记录媒体magnetic recording medium 磁性录音体magnetic recording system 磁记录装置magnetic regulator 磁力调节器magnetic relay timer 磁性继电定时器magnetic relay timer 磁性继电器定时器magnetic relay 磁性继电器magnetic reluctance 磁阻magnetic remanence 剩磁magnetic repulsion 磁拒斥magnetic repulsion 磁推斥magnetic resistance 磁阻magnetic retardation 磁滞magnetic retentivity 剩磁magnetic retentivity 顽磁性magnetic saturation 磁饱和magnetic screening 磁屏magnetic screening 磁屏蔽magnetic secular change 地磁长期变化magnetic semiconductor 磁性半导体magnetic sensor 磁性传感器magnetic separation 磁力分离magnetic shell 磁壳magnetic shielding 磁屏蔽magnetic shoal 具有磁干扰的浅水区magnetic shunt 磁分路magnetic silencer 电磁消声器magnetic silencer 电磁消音器magnetic sound recording film 磁性录音胶片magnetic sound recording 磁性录音magnetic south 磁南magnetic spark plug 电磁火花塞magnetic starter 磁力起动器magnetic steel 磁钢magnetic steel 磁性钢magnetic storage device 磁存储器magnetic storage 磁存储器magnetic storm 磁暴magnetic strain gauge 磁性应变仪magnetic strain 磁应变magnetic strainer 磁性滤器magnetic strength 磁场强度magnetic stress 磁应力magnetic substance 磁性材料magnetic surface storage 磁表面存储器magnetic survey 磁力探测magnetic susceptibility 磁化系数magnetic switch 磁力开关magnetic tachometer 磁力转速表magnetic tape buffer 磁带缓冲器magnetic tape cartridge 盒式磁带magnetic tape device 磁带装置magnetic tape driving system 磁带传动系统magnetic tape equipment 磁带装置magnetic tape head 磁带机磁头magnetic tape machine 磁带机magnetic tape memory 磁带存储器magnetic tape plotting system 磁带绘图系统magnetic tape reader 磁带读出器magnetic tape reader 磁带读数器magnetic tape recorder 磁带记录器magnetic tape start-stop time 磁带启停时间magnetic tape terminal equipment 磁带终端设备magnetic tape unit 磁带机magnetic tape unit 磁带机磁带装置magnetic tape unit 磁带装置magnetic tape 磁带magnetic test 磁力探伤magnetic thin film 磁性薄膜magnetic thrust bearing 磁性推力轴承magnetic tracing device 磁性跟踪装置magnetic track 磁道magnetic track 磁航迹向magnetic track 磁航迹向磁道magnetic transmission 磁力传动magnetic traveling crane 电磁吸盘式门式起重机magnetic traveling crane 电磁吸盘式门座起重机magnetic trip 电磁脱扣器magnetic type 磁铁型magnetic valve 电磁阀magnetic variation chart 磁偏差海图magnetic variation curves 磁差曲线magnetic variation 磁差magnetic variation 磁差;磁变化magnetic variation 磁罗经误差magnetic variation 磁性变化magnetic vice 磁力虎钳magnetic virgin state 未磁化状态magnetic viscosity 磁粘滞性magnetic water conditioner 磁性净水器magnetic wave 磁波magnetic wedge 磁性楔magnetic wire 磁线magnetic worktable 磁性工作台magnetic yoke 磁偏角系统magnetic yoke 磁轭magnetic yoke 磁轭;磁偏转系统magnetic yoke 磁轭磁偏角系统magnetic 磁的magnetic 磁的磁性的magnetic 磁的磁性的磁铁的magnetic 磁的磁性的磁性物质符号磁铁的magnetic 磁的磁性物质符号magnetic 磁性的magnetic-card unit 磁卡片机magnetic-core memory 磁心存储器magnetic-core switch 磁心开关magnetic-coupled 磁耦合的magnetic-coupling flowmeter 磁耦合式流量表magnetic-field pattern 磁场特性magnetic-film memory 磁膜存储器magnetic-mechanical 磁-机械的magnetic-particle inspection 磁粉探伤magnetic-synchro 磁同步的magneticabatement 消磁magneticaction 磁力作用magneticaging 磁老化magneticalloy 磁性合金magnetically suspended gyroscope 磁悬浮陀螺magneticamplifier 磁性放大器magneticanalysis 磁分析法magneticanisotropy 磁各向异性magneticannealing effect 磁致冷却效应magneticanomaly detection 磁性异常探测magneticattraction 磁吸引magneticautosteering gear 磁性自动操舵装置magneticbalance type 磁性平衡式magneticbiasing 磁偏magneticblow-out circuit breaker 磁吹灭弧断路器magneticblow-out 磁性灭弧magneticbody 磁体magneticbrake 磁力制动器magneticbridge 导磁率电桥magneticbubble device 磁泡器件magneticbubble 磁泡magneticcartridge 电磁式拾音头magneticcharacteristic 磁特性magneticcharge 磁荷magneticchart 电磁图magneticchuck 电磁吸盘magneticcircuit 磁路magneticclutch 电磁离合器magneticcoefficient 磁化系数magneticcompensator 磁性补偿器magneticconductance 磁导magneticconductivity 导磁率magneticcontactor 磁接触器magneticcontrol relay 磁控继电器magneticcontroller 磁控制器magneticcore 磁心magneticcoupling 电磁联轴器磁耦合magneticcrack detection 磁力探伤magneticcrane 电磁吸盘式起重机magneticdamper 磁性阻尼器magneticdamping 磁性阻尼magneticdeflection 磁致偏转magneticdeformation 磁性变形magneticdegree 磁角度magneticdelay-line 磁延迟线magneticdetection monitor 磁性探测监视器magneticdetection 磁性探伤magneticdetector 磁性检波器磁性探伤仪magneticdeviation 磁差magneticdial gauge 磁性指示表磁性千分表magneticdip 磁倾角magneticdipole 磁偶极子magneticdisc memory 磁盘存储器magneticdisc 磁盘magneticdispersion 磁漏magneticdisplacement 磁移magneticdistrubance 磁扰magneticdouble coil 双铁芯线圈magneticdrag-type tachometer 磁感应式转速表magneticdrill press 电磁钻床magneticdrive 磁力传动带电磁离合器的传动装置magneticdrum recorder 磁鼓记录器magneticdrum storage 磁鼓存储器magneticdrum 磁鼓magneticelement for lubricating oil 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generator 永磁发电机magneto microphone 电磁式送话器magneto resistance 磁阻magneto resistance=magnetoresistance 磁阻magneto switchboard 磁石式交换机magneto telephone 磁石式电话magneto 磁电机magneto 永磁发电机magneto-electric 磁电的magneto-gas dynamics 磁气体动力学magneto-ohmmeter 永磁发电机式电阻表magnetoconductivity 导磁率magnetocrystalline anisotropy 磁晶各向异性magnetocrystalline 磁晶magnetodynamo 直流发电机组高压永磁发电机magnetoelectric generator 磁电式发电机magnetoelectric machine 磁电式电机magnetoelectric machine 永磁电机magnetoelectric relay 磁电式继电器magnetoelectric tachometer 磁电式转速表magnetoelectric 磁电的magnetoelectric 电磁的magnetoelectrical 电磁的magnetoelectricity 磁电magnetoelectricity 磁电电磁学magnetogram 磁力图magnetogram 磁力图磁强记录图地磁记录图magnetogram 磁强图magnetograph 磁强记录仪magnetograph 地磁记录仪magnetographic inspection 磁力图示探伤magnetographic inspection 磁性图示探伤magnetohydrodynamic characteristic 磁流体动力特性magnetohydrodynamic generator 磁流体动力发电机magnetohydrodynamic gyroscope 磁流体动力陀螺仪magnetohydrodynamic plant 磁流体动力装置magnetohydrodynamic propulsion apparatus 磁流体动力推进装置magnetohydrodynamic propulsion plant 磁流体动力推进装置magnetohydrodynamic 磁流体动力的。

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The Fermi contour of the antibonding subband changes its shape, shrinks and, at a critical ﬁeld Bc,1, disappears. All electrons occupy only the bonding subband and form a wide single layer. The magnetoresistance approaches a pronounced minimum as the density of states (DOS) is halved and, therefore, also the electron scattering rate.
The aim of this paper is to study the inﬂuence of front- and back-gate voltages on the above mentioned critical ﬁelds.
Two samples grown by MBE were studied. The Sam-
Two types of structures with similar bonding and antibonding energy levels can be prepared: (i) The barrier is far from the interface and only a small part of electrons is in the triangular well. (ii) The barrier is close to the interface and the majority of electrons is in the triangular well.
Strongly asymmetric double-well structures were prepared (by MBE method) by inserting a thin Al0.3Ga0.7As barrier into the GaAs buﬀer layer of standard modulation-doped GaAs/Al0.3Ga0.7As heterostructures. The resulting double-well system consists of a nearly rectangular well and of a triangular well. The bonding and antibonding subbands are formed by tunnel-coupling of the ground states in individual wells.
The response of a structure to the applied in-plane magnetic ﬁeld depends on its type.
For both types the Fermi contours are two concentric circles at B = 0. The in-plane ﬁeld B induces a transfer of antibonding electrons to the bonding subband and the shift of the centre of mass of the electron layer closer to the interface [4].
Upon further increasing B , the system undergoes a transition from a single-layer to a bilayer state. A neck in the peanut-like Fermi contour becomes narrower and, at B = Bc,2, the contour splits into the Fermi lines of two independent electron sheets localized in the rectangular and triangular wells. At this second critical ﬁeld, the DOS has a logarithmic singularity and the magnetoresistance reaches a sharp maximum.
The occupancy of the wells can be further modiﬁed by applying front- or back-gate voltage. The back-gate voltage will inﬂuence strongly the structures of the ﬁrst type while the samples of the second type will be more sensitive to the front-gate voltage.
Abstract
We have investigated experimentally the magnetoresistance of strongly asymmetric double-wells. The structures were prepared by inserting a thin Al0.3Ga0.7As barrier into the GaAs buﬀer layer of a standard modulation-doped GaAs/Al0.3Ga0.7As heterostructure. The resulting double-well system consists of a nearly rectangular well and of a triangular well coupled by tunneling through the thin barrier. With a proper choice of the barrier parameters one can control the occupancy of the two wells and of the two lowest (bonding and antibonding) subbands. The electron properties can be further inﬂuenced by applying front- or back-gate voltage.
1
∆ρxx/ρxx(0)
0.5
∆g/g(0)
0−0.5Fra bibliotek−1 0
Bc1 5
1 Corresponding author. E-mail: smrcka@fzu.cz
Preprint submitted to Physica E
to the single layer state due to depletion of the triangular well.
2. Experiments
Key words: Double-layer two-dimensional electron system, Magnetotransport, Gate voltage PACS: 74.40.Xy, 71.63.Hk
1. Introduction
A magnetic ﬁeld B applied parallel to the quasi-twodimensional systems of electrons conﬁned in doublewell structures is known to couple strongly to the electron orbital motion and to change dramatically the electron energy spectra. The magnetoresistance oscillation observed on coupled double quantum wells represents a striking manifestation of van Hove singularities in the B -dependent density of states, corresponding to the depopulation of the antibonding subband at a critical ﬁeld B = Bc,1, and to the splitting of the Fermi sea into two separated electron sheets at a second critical ﬁeld Bc,2 [1,2,3,4]. There can also be the third critical ﬁeld Bc,3 [5] at which the system returns
aInstitute of Physics ASCR, Cukrovarnick´a 10, 162 53 Praha 6, Czech Republic bGrenoble High Magnetic Field Laboratory, Boˆıte Postale 166 , 38042 Grenoble Cedex 09, France
The resulting separation of the bonding and antibonding levels depends on the position and on the
2 February 2008
∆g/g(0) (%) ∆ρxx/ρxx(0) (%)
thickness of the barrier. The minimum separation is achieved if the barrier is located close to the center of mass of the two-dimensional electron layer. With the barrier closer to or farer from the interface the bonding and antibonding subbands become more separated.