简易英语物理实验报告report
大学物理实验报告英文版--声速测量
Physical Lab Report : Measurement of speed of soundWriter: No.Experiment date: 31.10.2012&7.11.2012Report date:10.11.2012In this class,we start to do an experiment b y only one person,which is named“measurement of speed of sound”.In fact,we are required to measure the wavelength and the frequency at the same same according to the formula“λf v =” .We can measure the frequency using the oscilloscope.And there are several about 15 minutes,I become familiar with them and begin operating my experiment.Experiment ing the resonance methodIn order to make the error smaller,I first move S2 to the position about mm x 100= ,then ,I move the S2 until first received amplitude reaches maximum.At the same time,I set the digital indicator to “mm 0”and record it,which makes following records easier.When f =38.629Hz,the records are as followed:There are two methods available to get an average distance from which we calculate the wavelength.The average,49.42mm =so mm 98.9=λ.then,m/s mm f v 346.898.98Hz 629.38=⨯==λ.The averagemm 48.42=.so ./12.34696.8Hz 629.38,96.8s m mm f v mm =⨯===λλCombining the method A and B,the average speed of sound is m/s 346.51v 1=.Experiment ing phase comparison methodIn this experiment,I was excited to see the so-called Lissajous curves.But I met a problem when I try to read the position of S 2 when the curv es collapses into straight line to “ ”,while it is OK to read when it shows“ ”.Thus,I found a solution to deal with this problem-----I only recorded the position of S 2 when the Lissajous curve showed “ ”.Then I must be careful that the phase between two record is 2π when doing data analysis later.Also,there are two methods to get the wavelength:A.Successive subtraction method:x 9-x 1 x 10-x 2 x 11-x 3 x 12-x 4x 13-x 5x 14-x 6x 15-x 7x 16-x 8Unit(mm ) 79.26 80.64 80.73 80.85 80.47 82.55 82.64 83.05 )(8mm x∆=λ 9.9010.0810.0910.1010.0510.3210.3310.38The average mm 15.10=λ.then,m/s mm f v 350.8115.01Hz 563.34=⨯==λ.e a linear fit x i -x 1=(i -1)λ/2i2 3 4 5 6 7 8 9 10 11 12 13141516)(11mm i x x i --=λ8.9 9.90 9.83 9.99 9.77 9.84 9.86 9.90 9.96 10.05 10.0310.0310.1110.1210.14The average ./17.34290.9Hz 563.34,90.9s m mm f v mm =⨯===λλCombining the method A and B,the average speed of sound is m/s 346.49v 2=Experiment ing timing methodIn fact,timing method is the first method I thought of when I want to measure the speed of sound.Because the basic formula “tLv ∆∆=”is almost the first physical formula we have learned. Now comes the problem that how to calculate the v since we have the formula as a principle.Then I recalled the first experiment we did to measure the spring constant.We made a linear fit of ∆x vs m ,the slope of which is just the k.Similarly,I collect all the data and then make a linear fit of L ∆ vs ∆t,the slope of which is just the speed of sound.The data recorded is as followed: t/μs 404 433 460 490 519 546 575 605 634 L/mm100110120130140150160170180After putting all the data to SI unit ,the form is: t/s 0.000404 0.000433 0.00046 0.00049 0.000519 0.000546 0.000575 0.000605 0.000634 L/m0.10.110.120.130.140.150.160.170.18Then I use a mathematic tool to make a linear fit of L vs t ,the graph is :According to the graph,we see R 2=0.9999,indicating that L and t are quite linearly correlative.Besides,we know the slope is the speed of sound,i.e,we conclude that m/s 348.40v 3=.Experiment ing timing method to measure the speed of sound in waterAfter finishing the first three experiments measuring the speed of sound in air,I filled the apparatus with water,and did the experiment similar to the experiment 3 to measure the sound speed in water. The data recorded is as followed: t/μs 94 100 107 114 121 127 134 141 148 L/mm100110120130140150160170180After putting all the data to SI unit ,the form is: t/s 0.00094 0.000100 0.000107 0.000114 0.000121 0.000127 0.000134 0.000141 0.000148 L/m0.10.110.120.130.140.150.160.170.18Then I use the mathematic tool to make a linear fit of L vs t ,the graph is :Also,from the graph,I see R 2=0.9997,indicating that L and t in water are also well linearly correlative.Similarly,weconclude that the speed of sound in water m/s 1477.4v water =.Discussion and conclusionThere are several factors contributing to the errors:①The distance between S1 and S2 is not always appropriate.For example,maybe I set the initial distance to be 100mm,but as I move S2 slowly away from S1,the distance become larger,which may make the transmission less sensitive,causing errors in the time.②In the experiment using resonance method,we need to judge that the oscillation amplitude in the detected signal reaches the maximum.Thus comes the problem how to judge.It ’s all up to ourselves!And this is also where errors come.③During a method,I had to keep the frequency unchanging,however,though I had try my best to keep it constant,it still changed,which can ’t be avoided by person.④As a matter of fact,when the sound transmit for a short distance,it may not strictly obey a simple harmonic wave,but we simplify the complexity when doing data analysis.Conclusion for the experimentwe use three methods to measure the sound of speed in air,the results are: m/s 346.51v 1= , m/s 346.49v 2= , m/s 348.40v 3= Besides the speed of sound in water is m/s 1477.4v water =.That is to say,the speed in water is approximately 4.3 times of that in air.In fact,this is very important in life.For example ,sonar is an application.It can measure the distance as well as explore things in water.This confirms that physics is always around our life and very useful .。
关于反应速度的物理实验报告 physics report regarding reaction time
Brief introduction: this is a report about a reaction test, we do the experiment a few times and try to improve the precision of the test. Each time we test how far the ruler fall, and use the formula: s=1/2g（9.8n/s）t(square) to calculate the reaction time of each person. And we also find some differences between right hand and left time in reaction time. And the apparatus we used was a wooden ruler(about 100cm long). I made a hypothesis that right hand might have a less reaction time than the one of the left hand.We do the first test about AAAAA’s reaction time(student id:19089), and it turned out AAAAA successfully catch the ruler after it had fallen approximately 37cm when using his right hand to grab, and about 30cm when using his left hand. Hence AAAAA’s reaction time is about 0.27s for right hand.However, we found that our data would not be accurate since we haven’t controlled original speed. So we decide to do this again and limited the height between the hand and the ruler. We lifted the ruler for 26cm and drop it without warning in order to test AAAAA’s reaction time. And the result turned out the ruler fell 40cm when using the right hand to grab, but it only fell approximately 25cm when using his left hand to grab. And his reaction time for left hand and the right hand was 0.22s and 0.28s.Next we tested BBBBB’s reaction time. We decided to set the original speed into 0 by putting the ruler just on top of his hands and to test few more times in order to make the results more accurate. And the results are:Right hand 15cm 14cm 15cm average 14.6 0.17sLeft hand 19cm 15cm 18cm average 17.3 0.19sIn conclusion, due to experiments we have done, we are able to argue that the reaction time of the left and right hand is different among different people maybe because some people are left-handed and the others are right-handed. However researches have shown that usually the left hand should have less reaction time because the left hand is controlled by the right brain which is responsible for perceptual space and perceptual function of the body.Independent value: the distance between hand and rulerDependent value: the reaction time。
Lab-report-物理实验报告(英文)
IntroductionCapacitor is widely used in a variety of fields as it can store electric energy, such as Filtering, resonant circuit and moving phase. Different capacitors have different abilities to store energy, which is due to the difference of capacitance. Capacitance is the ability of a capacitor to store charge in an electric field, it is also a measure of the amount of electric potential energy stored (or separated) for a given electric potential. This report is going to investigate the capacitance of a capacitor made from the experiment by using different DC methods. Before the capacitor made from the experiment is measured, three DC methods will be tested to verify whether these methods are efficient by measuring the capacitance of the known capacitor. In addition, after measuring the unknown capacitor, the whole capacitors will be connected in parallel and the total size of capacitance will be measured.Theory Capacitance can be found by using:dA C r ⨯⨯=εε0. This is for two flat plates. As for the formula, C is the capacitance of a capacitor, A is the area of flat plates, d is the distance between the two flat plates, 0ε is the permittivity of vacuum, r ε is the relative permittivity. Permittivity is constant of proportionality that relates the electric field in a material to the electric displacement in that material and relative permittivity is the ratio of the permittivity of a substance tothat of free space or vacuum. Different materials have different relative permittivity, the behind table includes the relative permittivity of some different material:Source: (The Engineering Tool Box, 2011.) When two capacitors are placed in series, the charge on each plate is of equalof charges on plate and V is the voltage across the capacitor). When ais the initial voltage adding on the capacitor, e is a constant and it is 2.718, R is resistance, C is capacitance and 0I is the initial current flowing through the capacitor). Analogously, when a capacitor is discharged, it flows RC t e V V -=0and RC t eI I -=0.MethodsApparatus :Power supply, leads, ruler, calipers, clips, known capacitor, aluminum foil,。
大学物理实验报告 英文版
大学物理实验报告Ferroelectric Control of Spin PolarizationControlling the spin degree of freedom by purely electrical means is currently an important challenge in spintronics (1, 2). Approaches based on spin-transfer torque (3) have proven very successful in controlling the direction of magnetization in a ferromagnetic layer, but they require the injection of high current densities. An ideal solution would rely on the application of an electric field across an insulator, as in existing nanoelectronics. Early experiments have demonstrated the volatile modulation of spin-based properties with a gate voltage applied through a dielectric. Notable examples include the gate control of the spin-orbit interaction in III-V quantum wells (4), the Curie temperature T C (5), or the magnetic anisotropy (6) in magnetic semiconductors with carrier-mediated exchange interactions; for example, (Ga,Mn)As or (In,Mn)As. Electric field–induced modifications of magnetic anisotropy at room temperature have also been reported recently in ultrathin Fe-based layers (7, 8).A nonvolatile extension of this approach involves replacing the gate dielectric by a ferroelectric and taking advantage of the hysteretic response of its order parameter (polarization) with an electric field. When combined with (Ga,Mn)As channels, for instance, a remanent control of T C over a few kelvin was achieved through polarization-driven charge depletion/accumulation (9, 10), and the magnetic anisotropy was modified by the coupling of piezoelectricity and magnetostriction (11, 12). Indications of an electrical control of magnetization have also been provided in magnetoelectric heterostructures at room temperature (13–17).Recently, several theoretical studies have predicted that large variations of magnetic properties may occur at interfaces between ferroelectrics and high-T C ferromagnets such as Fe (18–20), Co2MnSi (21), or Fe3O4 (22). Changing the direction of the ferroelectric polarization has been predicted to influence not only the interfacial anisotropy and magnetization, but also the spin polarization. Spin polarization [., the normalized difference in the density of states (DOS) of majority and minority spin carriers at the Fermi level (E F)] is typically the key parameter controlling the response of spintronics systems, epitomized by magnetic tunnel junctions in which the tunnel magnetoresistance (TMR) is related to the electrode spin polarization by the Jullière formula (23). These predictions suggest that the nonvolatile character of ferroelectrics at the heart of ferroelectric random access memory technology (24) may be exploited in spintronics devices such as magnetic random access memories or spin field-effect transistors (2). However, the nonvolatile electrical control of spin polarization has not yet been demonstrated.We address this issue experimentally by probing the spin polarization of electrons tunneling from an Fe electrode through ultrathin ferroelectric BaTiO3 (BTO) tunnel barriers (Fig. 1A). The BTO polarization can be electrically switched to point toward or away from the Fe electrode. We used a half-metallic (25) bottom electrode as a spin detector in these artificial multiferroic tunnel junctions (26, 27). Magnetotransport experiments provide evidence for a large and reversible dependence of the TMR on ferroelectric polarization direction.Fig. 1(A) Sketch of the nanojunction defined by electrically controlled nanoindentation. A thin resist is spin-coated on the BTO(1 nm)/LSMO(30 nm) bilayer. The nanoindentation is performed with a conductive-tip atomic force microscope, and the resulting nano-hole is filled by sputter-depositing Au/CoO/Co/Fe. (B) (Top) PFM phase image of a BTO(1 nm)/LSMO(30 nm) bilayer after poling the BTO along 1-by-4–μm stripes with either a negative or positive (tip-LSMO) voltage. (Bottom) CTAFM image of an un poled area of a BTO(1 nm)/LSMO(30 nm) bilayer. Ω, ohms. (C) X-ray absorption spectra collected at room temperature close to the Fe L3,2 (top), Ba M5,4 (middle), and Ti L3,2 (bottom) edges on an AlO x nm)/Al nm)/Fe(2 nm)/BTO(1 nm)/LSMO(30 nm)(D) HRTEM and (E) HAADF images of the Fe/BTO interface in a Ta(5 nm)/Fe(18 nm)/BTO(50 nm)/LSMO(30 nm)The white arrowheads in (D) indicate the lattice fringes of {011} planes in the iron layer. [110] and [001] indicate pseudotetragonal crystallographic axes of the BTO perovskite.The tunnel junctions that we used in this study are based on BTO(1 nm)/LSMO(30 nm) bilayers grown epitaxially onto (001)-oriented NdGaO3 (NGO) single-crystal substrates (28). The large (~180°) and stable piezoresponse force microscopy (PFM) phase contrast (28) between negatively and positively poled areas (Fig. 1B, top) indicates that the ultrathin BTO films are ferroelectric at room temperature (29). The persistence of ferroelectricity for such ultrathin films of BTO arises from the large lattice mismatch with the NGO substrate (–%), which is expected to dramatically enhance ferroelectric properties in this highly strained BTO (30). The local topographical and transport properties of the BTO(1 nm)/LSMO(30 nm) bilayers were characterized by conductive-tip atomic force microscopy (CTAFM) (28). The surface is very smooth with terraces separated by one-unit-cell–high steps, visible in both the topography (29) and resistance mappings (Fig. 1B, bottom). No anomalies in the CTAFM data were observed over lateral distances on the micrometer scale.We defined tunnel junctions from these bilayers by a lithographic technique based on CTAFM (28, 31). Top electrical contacts of diameter ~10 to 30 nm can be patterned by this nanofabrication process. The subsequent sputter deposition of a 5-nm-thick Fe layer, capped by a Au(100 nm)/CoO nm)/Co nm) stack to increase coercivity, defined a set of nanojunctions (Fig. 1A). The same Au/CoO/Co/Fe stack was deposited on another BTO(1 nm)/LSMO(30 nm) sample for magnetic measurements. Additionally, a Ta(5 nm)/Fe(18 nm)/BTO(50 nm)/LSMO(30 nm) sample and a AlO x nm)/Al nm)/Fe(2 nm)/BTO(1 nm)/LSMO(30 nm) sample were realized for structural and spectroscopic characterizations.We used both a conventional high-resolution transmission electron microscope (HRTEM) and the NION UltraSTEM 100 scanning transmission electron microscope (STEM) to investigate the Fe/BTO interface properties of the Ta/Fe/BTO/LSMO sample. The epitaxial growth of the BTO/LSMO bilayer on the NGO substrate was confirmed by HRTEM and high-resolution STEM images. The low-resolution, high-angle annular dark field (HAADF) image of the entire heterostructure shows the sharpness of the LSMO/BTO interface over the studied area (Fig. 1E, top). Figure 1D reveals a smooth interface between the BTO and the Fe layers. Whereas the BTO film is epitaxially grown on top of LSMO, the Fe layer consists of textured nanocrystallites. From the in-plane (a) and out-of-plane (c) lattice parameters in the tetragonal BTO layer, we infer that c/a = ± , in good agreement with the value of found with the use of x-ray diffraction (29). The interplanar distances for selected crystallites in the Fe layer [., ~ Å (Fig. 1D, white arrowheads)] are consistent with the {011} planes of body-centered cubic (bcc) Fe.We investigated the BTO/Fe interface region more closely in the HAADF mode of the STEM (Fig. 1E, bottom). On the BTO side, the atomically resolved HAADF image allows the distinction of atomic columns where the perovskite A-site atoms (Ba) appear as brighter spots. Lattice fringes with the characteristic {100} interplanar distances of bcc Fe (~ Å) can be distinguished on the opposite side. Subtle structural, chemical, and/or electronic modifications may be expected to occur at the interfacial boundary between the BTO perovskite-type structure and the Fe layer. These effects may lead to interdiffusion of Fe, Ba, and O atoms over less than 1 nm, or the local modification of the Fe DOS close to E F, consistent with ab initio calculations of the BTO/Fe interface (18–20).To characterize the oxidation state of Fe, we performed x-ray absorption spectroscopy (XAS) measurements on a AlO x nm)/Al nm)/Fe(2 nm)/BTO(1 nm)/LSMO(30 nm) sample (28). The probe depth was at least 7 nm, as indicated by the finite XAS intensity at the La M4,5 edge (28), so that the entire Fe thickness contributed substantially to the signal. As shown in Fig. 1C (top), the spectrum at the Fe L2,3 edge corresponds to that of metallic Fe (32). The XAS spectrum obtained at the Ba M4,5 edge (Fig. 1C, middle) is similar to that reported for Ba2+ in (33). Despite the poor signal-to-noise ratio, the Ti L2,3 edge spectrum (Fig. C, bottom) shows the typical signature expected for a valence close to 4+ (34). From the XAS, HRTEM, and STEM analyses, we conclude that the Fe/BTO interface is smooth with no detectable oxidation of the Fe layer within a limit of less than 1 nm.After cooling in a magnetic field of 5 kOe aligned along the [110] easy axis of pseudocubic LSMO (which is parallel to the orthorhombic [100] axis of NGO), we characterized the transport properties of the junctions at low temperature K). Figure 2A (middle) shows a typical resistance–versus–magnetic field R(H) cycle recorded at a bias voltage of –2 mV (positive bias corresponds to electrons tunneling from Fe to LSMO). The bottom panel of Fig. 2A shows the magnetic hysteresis loop m(H) of a similar unpatterned sample measured with superconducting quantum interference device (SQUID) magnetometry. When we decreased the magnetic field from a large positive value, the resistance dropped in the –50 to –250 Oe range and then followed a plateau down to –800 Oe, after which it sharply returned to the high-resistance state. We observed a similar response when cycling the field back to large positive values. A comparison with the m(H) loop indicates that the switching fields in R(H) correspond to changes in the relative magnetic configuration of the LSMO and Fe electrodes from parallel (at high field) to antiparallel (at low field). The magnetically softer LSMO layer switched at lower fields (50 to 250 Oe) compared with the Fe layer, for which coupling to the exchange-biased Co/CoO induces larger and asymmetric coercive fields (–800 Oe, 300 Oe). The observed R(H) corresponds to a negative TMR = (R ap–R p)/R ap of –17%[R p and R ap are the resistance in the parallel (p) and antiparallel (ap) magnetic configurations, respectively; see the sketches in Fig. 2A]. Within the simple Jullière model of TMR (23) and considering the large positive spin polarization of half-metallic LSMO (25), this negative TMR corresponds to a negative spin polarization for bcc Fe at the interface with BTO, in agreement with ab initio calculations (18–20).Fig. 2(A) (Top) Device schematic with black arrows to indicate magnetizations. p, parallel; ap, antiparallel. (Middle) R(H) recorded at –2 mV and K showing negative TMR. (Bottom) m(H) recorded at 30 K with a SQUID magnetometer. emu, electromagnetic units. (B) (Top) Device schematic with arrows to indicate ferroelectric polarization. (Bottom) I(V DC) curves recorded at K after poling the ferroelectric down (orange curve) or up (brown curve). The bias dependence of the TER is shown in the inset.As predicted (35–38) and demonstrated (29) previously, the tunnel current across a ferroelectric barrier depends on the direction of the ferroelectric polarization. We also observed this effect in our Fe/BTO/LSMO junctions. As can be seen in Fig. 2B, after poling the BTO at K to orient its polarization toward LSMO or Fe (with a poling voltage of VP–≈ –1 V or VP+≈ 1 V, respectively; see Fig. 2B sketches), current-versus-voltage I(V DC) curves collected at low bias voltages showed a finite difference corresponding to a tunnel electroresistance as large as TER = (I VP+–I VP–)/I VP–≈ 37% (Fig. 2B, inset). This TER can be interpreted within an electrostatic model (36–39), taking into account the asymmetric deformation of the barrier potential profile that is created by the incomplete screening of polarization charges by different Thomas-Fermi screening lengths at Fe/BTO and LSMO/BTO interfaces. Piezoelectric-related TER effects (35, 38) can be neglected as the piezoelectric coefficient estimated from PFM experiments is too small in our clamped films (29). TER measurements performed on a BTO(1 nm)/LSMO(30 nm) bilayer with the use of a CTAFM boron-doped diamond tip as the top electrode showed values of ~200% (29). Given the strong sensitivity of the TER on barrier parameters and barrier-electrode interfaces, these two values are not expected to match precisely. We anticipate that the TER variation between Fe/BTO/LSMO junctions and CTAFM-based measurements is primarily the result of different electrostatic boundary conditions.Switching the ferroelectric polarization of a tunnel barrier with voltage pulses is also expected to affect the spin-dependent DOS of electrodes at a ferromagnet/ferroelectric interface. Interfacial modifications of the spin-dependent DOS of the half-metallic LSMO by the ferroelectric BTO are not likely, as no states are present for the minority spins up to ~350 meV above E F (40, 41). For 3d ferromagnets such as Fe, large modifications of the spin-dependent DOS are expected, as charge transfer between spin-polarized empty and filled states is possible. For the Fe/BTO interface, large changes have been predicted through ab initio calculations of 3d electronic states of bcc Fe at theinterface with BTO by several groups (18–20).To experimentally probe possible changes in the spin polarization of the Fe/BTO interface, we measured R(H) at a fixed bias voltage of –50 mV after aligning the ferroelectric polarization of BTO toward Fe or LSMO. R(H) cycles were collected for each direction of the ferroelectric polarization for two typical tunnel junctions of the same sample (Fig. 3, B and C, for junction #1; Fig. 3, D and E, for junction #2). In both junctions at the saturating magnetic field, high- and low-resistance states are observed when the ferroelectric polarization points toward LSMO or Fe, respectively, with a variation of ~ 25%. This result confirms the TER observations in Fig. 2B.Fig. 3(A) Sketch of the electrical control of spin polarization at the Fe/BTO interface. (B and C) R(H) curves for junction #1 (V DC = –50 mV, T = K) after poling the ferroelectric barrier down or up, respectively.(D and E) R(H) curves for junction #2 (V DC = –50 mV, T= K) after poling the ferroelectric barrier down or up, respectively.More interestingly, here, the TMR is dramatically modified by the reversal of BTO polarization. For junction #1, the TMR amplitude changes from –17 to –3% when the ferroelectric polarization is aligned toward Fe or LSMO, respectively (Fig. 3, B and C). Similarly for junction #2, the TMR changes from –45 to –19%. Similar results were obtained on Fe/BTO nm)/LSMO junctions (28). Within the Jullière model (23), these changes in TMR correspond to a large (or small) spin polarization at the Fe/BTO interface when the ferroelectric polarization of BTO points toward (or away from) the Fe electrode. These experimental data support our interpretation regarding the electrical manipulation of the spin polarization of the Fe/BTO interface by switching the ferroelectric polarization of the tunnel barrier.To quantify the sensitivity of the TMR with the ferroelectric polarization, we define a term, the tunnel electromagnetoresistance, as TEMR = (TMR VP+–TMR VP–)/TMR VP–. Large values for the TEMR are found for junctions #1 (450%) and #2 (140%), respectively. This electrical control of the TMR with the ferroelectric polarization is repeatable, as shown in Fig. 4 for junction #1 where TMR curves are recorded after poling the ferroelectric up, down, up, and down, sequentially (28).Fig. 4TMR(H) curves recorded for junction #1 (V DC = –50 mV, T = K) after poling the ferroelectric up (VP+), down (VP–), up (VP+), and down (VP–).For tunnel junctions with a ferroelectric barrier and dissimilar ferromagnetic electrodes, we have reported the influence of the electrically controlled ferroelectric barrier polarization on the tunnel-current spin polarization. This electrical influence over magnetic degrees of freedom represents a new and interfacial magnetoelectric effect that is large because spin-dependent tunneling is very sensitive to interfacial details. Ferroelectrics can provide a local, reversible, nonvolatile, and potentially low-power means of electrically addressing spintronics devices. Supporting Online Materialand MethodsFigs. S1 to S5ReferencesReceived for publication 30 October 2009.Accepted for publication 4 January 2010.References and NotesC. Chappert, A. Fert, F. N. Van Dau, The emergence of spin electronics in data storage. Nat. Mater. 6,813 (2007).I. Žutić, J. Fabian, S. Das Sarma, Spintronics: Fundamentals and applications. Rev. Mod. Phys. 76,323 (2004).J. C. Slonczewski, Current-driven excitation of magnetic multilayers. J. Magn. Magn. Mater. 159, L1(1996).J. Nitta, T. Akazaki, H. Takayanagi, T. Enoki, Gate control of spin-orbit interaction in an inverted heterostructure. Phys. Rev. Lett. 78, 1335 (1997).H. Ohno et al., Electric-field control of ferromagnetism. Nature 408, 944 (2000).D. Chiba et al., Magnetization vector manipulation by electric fields. Nature 455, 515 (2008).M. Weisheit et al., Electric field–induced modification of magnetism in thin-film ferromagnets. Science315, 349 (2007).T. Maruyama et al., Large voltage-induced magnetic anisotropy change in a few atomic layers of . Nanotechnol. 4, 158 2009).S. W. E. Riester et al., Toward a low-voltage multiferroic transistor: Magnetic (Ga,Mn)As under ferroelectric control. Appl. Phys. Lett. 94, 063504 (2009).I. Stolichnov et al., Non-volatile ferroelectric control of ferromagnetism in (Ga,Mn)As. Nat. Mater. 7, 464(2008).C. Bihler et al., Ga1−x Mn x As/piezoelectric actuator hybrids: A model system for magnetoelasticmagnetization manipulation. Phys. Rev. B 78, 045203 (2008).M. Overby, A. Chernyshov, L. P. Rokhinson, X. Liu, J. K. Furdyna, GaMnAs-based hybrid multiferroic memory device. Appl. Phys. Lett. 92, 192501 (2008).C. Thiele, K. Dörr, O. Bilani, J. Rödel, L. Schultz, Influence of strain on the magnetization and magnetoelectric effect in 75, 054408 (2007).W. Eerenstein, M. Wiora, J. L. Prieto, J. F. Scott, N. D. Mathur, Giant sharp and persistent converse magnetoelectric effects in multiferroic epitaxial heterostructures. Nat. Mater. 6, 348 (2007).T. Kanki, H. Tanaka, T. Kawai, Electric control of room temperature ferromagnetism in a Pb field-effect transistor. Appl. Phys. Lett. 89, 242506 (2006).. Chu et al., Electric-field control of local ferromagnetism using a magnetoelectric multiferroic. Nat. Mater. 7, 478 2008).S. Sahoo et al., Ferroelectric control of magnetism in BaTiO3∕Fe heterostructures via interface strain coupling. Phys. Rev. B 76, 092108 (2007).. Duan, S. S. Jaswal, E. Y. Tsymbal, Predicted magnetoelectric effect in Fe/BaTiO3 multilayers: Ferroelectric control of magnetism. Phys. Rev. Lett. 97, 047201 (2006).M. Fechner et al., Magnetic phase transition in two-phase multiferroics predicted from first . Rev.B 78, 212406 (2008).J. Lee, N. Sai, T. Cai, Q. Niu, A. A. Demkov, preprint available at abs/.K. Yamauchi, B. Sanyal, S. Picozzi, Interface effects at a half-metal/ferroelectric junction. Appl. Phys. Lett. 91, 062506 (2007).M. K. Niranjan, J. P. Velev, . Duan, S. S. Jaswal, E. Y. Tsymbal, Magnetoelectric effect at the Fe3O4/BaTiO3 (001) interface: A first-principles study. Phys. Rev.B 78, 104405 (2008).M. Jullière, Tunneling between ferromagnetic films. Phys. Lett. A 54, 225 (1975).J. F. Scott, Applications of modern ferroelectrics. Science 315, 954 (2007).M. Bowen et al., Nearly total spin polarization in La2/3Sr1/3MnO3 from tunneling experiments. Appl. Phys. Lett. 82, 233 (2003).J. P. Velev et al., Magnetic tunnel junctions with ferroelectric barriers: Prediction of four resistance states from first principles. Nano Lett. 9, 427 (2009).F. Yang et al., Eight logic states of tunneling magnetoelectroresistance in multiferroic tunnel . Appl. Phys. 102, 044504 (2007).Materials and methods are available as supporting material on Science Online.V. Garcia et al., Giant tunnel electroresistance for non-destructive readout of ferroelectric states. Nature460, 81 (2009).K. J. Choi et al., Enhancement of ferroelectricity in strained BaTiO3 thin films. Science 306, 1005(2004). K. Bouzehouane et al., Nanolithography based on real-time electrically controlled indentation with an atomic force microscope for nanocontact elaboration. Nano Lett. 3, 1599 (2003).T. J. Regan et al., Chemical effects at metal/oxide interfaces studied by x-ray-absorption . Rev.B 64, 214422 (2001).N. Hollmann et al., Electronic and magnetic properties of the kagome systems YBaCo4O7 and YBaCo3M O7 (M=Al, Fe). Phys. Rev. B 80, 085111 (2009).M. Abbate et al., Soft-x-ray-absorption studies of the location of extra charges induced by substitution in controlled-valence materials. Phys. Rev. B 44, 5419 (1991).E. Y. Tsymbal, H. Kohlstedt, Tunneling across a ferroelectric. Science 313, 181 (2006).M. Ye. Zhuravlev, R. F. Sabirianov, S. S. Jaswal, E. Y. Tsymbal, Giant electroresistance in ferroelectric tunnel junctions. Phys. Rev. Lett. 94, 246802 (2005).M. Ye. Zhuravlev, R. F. Sabirianov, S. S. Jaswal, E. Y. Tsymbal, Erratum: Giant electroresistance in ferroelectric tunnel junctions. Phys. Rev. Lett. 102, 169901 2009).H. Kohlstedt, N. A. Pertsev, J. Rodriguez Contreras, R. Waser, Theoretical current-voltage characteristics of ferroelectric tunnel junctions. Phys. Rev. B 72, 125341 (2005).M. Gajek et al., Tunnel junctions with multiferroic barriers. Nat. Mater. 6, 296 (2007).M. Bowen et al., Spin-polarized tunneling spectroscopy in tunnel junctions with half-metallic . Rev. Lett. 95, 137203 (2005).J. D. Burton, E. Y. Tsymbal, Prediction of electrically induced magnetic reconstruction at the manganite/ferroelectric interface. Phys. Rev. B 80, 174406 (2009).We thank R. Guillemet, C. Israel, M. E. Vickers, R. Mattana, . George, and P. Seneor for technical assistance, and C. Colliex for fruitful discussions on the microscopy measurements. This study was partially supported by the . Partenariat Hubert Curien Alliance program, the French Réseau Thématique de Recherche Avancée Triangle de la Physique, the European Union (EU) Specific Targeted Research Project (STRep) Manipulating the Coupling in Multiferroic Films, EU STReP Controlling Mesoscopic Phase Separation, . Engineering and Physical Sciences Research Council grant EP/E026206/I, French C-Nano Île de France, French Agence Nationale de la Recherche (ANR) Oxitronics, French ANR Alicante, the European Enabling Science and Technology through European Elelctron Microscopy program, and the French Microscopie Electronique et Sonde Atomique network. .acknowledges support from Comissionat per a Universitats i Recerca (Generalitat de Catalunya).。
英语作文物理电学实验报告
英语作文物理电学实验报告Physics Experiment Report on Electric Circuits。
Introduction。
Electric circuits are important in our daily lives as they form the basis of all electrical devices. In this experiment, we investigated the behavior of electric circuits, including Ohm's law, Kirchhoff's laws, and the behavior of resistors in series and parallel.Materials。
Power supply。
Ammeter。
Voltmeter。
Resistors (varying values)。
Wires。
Breadboard。
Procedure。
1. Set up the circuit as shown in the diagram below, using a breadboard to connect the components.2. Measure the voltage across the resistor using the voltmeter and record the value.3. Measure the current flowing through the resistor using the ammeter and record the value.4. Repeat steps 2-3 for different values of resistors.5. Connect resistors in series and parallel and measure the voltage and current across each resistor.Results。
大学物理实验报告 英文版
大学物理实验报告Ferroelectric Control of Spin PolarizationABSTRACTA current drawback of spintronics is the large power that is usually required for magnetic writing, in contrast with nanoelectronics, which relies on “zero-current,” gate-controlled operations. Efforts have been made to control the spin-relaxation rate, the Curie temperature, or the magnetic anisotropy with a gate voltage, but these effects are usually small and volatile. We used ferroelectric tunnel junctions with ferromagnetic electrodes to demonstrate local, large, and nonvolatile control of carrier spin polarization by electrically switching ferroelectric polarization. Our results represent a giant type of interfacial magnetoelectric coupling and suggest a low-power approach for spin-based information control.Controlling the spin degree of freedom by purely electrical means is currently an important challenge in spintronics (1, 2). Approaches based on spin-transfer torque (3) have proven very successful in controlling the direction of magnetization in a ferromagnetic layer, but they require the injection of high current densities. An ideal solution would rely on the application of an electric field across an insulator, as in existing nanoelectronics. Early experiments have demonstrated the volatile modulation of spin-based properties with a gate voltage applied through a dielectric. Notable examples include the gate control of the spin-orbit interaction in III-V quantum wells (4), the Curie temperature T C (5), or the magnetic anisotropy (6) in magnetic semiconductors with carrier-mediated exchange interactions; for example, (Ga,Mn)As or (In,Mn)As. Electric field–induced modifications of magnetic anisotropy at room temperature have also been reported recently in ultrathin Fe-based layers (7, 8).A nonvolatile extension of this approach involves replacing the gate dielectric by a ferroelectric and taking advantage of the hysteretic response of its order parameter (polarization) with an electric field. When combined with (Ga,Mn)As channels, forinstance, a remanent control of T C over a few kelvin was achieved through polarization-driven charge depletion/accumulation (9, 10), and the magnetic anisotropy was modified by the coupling of piezoelectricity and magnetostriction (11, 12). Indications of an electrical control of magnetization have also been provided in magnetoelectric heterostructures at room temperature (13–17).Recently, several theoretical studies have predicted that large variations of magnetic properties may occur at interfaces between ferroelectrics and high-T C ferromagnets such as Fe (18–20), Co2MnSi (21), or Fe3O4 (22). Changing the direction of the ferroelectric polarization has been predicted to influence not only the interfacial anisotropy and magnetization, but also the spin polarization. Spin polarization [i.e., the normalized difference in the density of states (DOS) of majority and minority spin carriers at the Fermi level (E F)] is typically the key parameter controlling the response of spintronics systems, epitomized by magnetic tunnel junctions in which the tunnel magnetoresistance (TMR) is related to the electrode spin polarization by the Jullière formula (23). These predictions suggest that the nonvolatile character of ferroelectrics at the heart of ferroelectric random access memory technology (24) may be exploited in spintronics devices such as magnetic random access memories or spin field-effect transistors (2). However, the nonvolatile electrical control of spin polarization has not yet been demonstrated.We address this issue experimentally by probing the spin polarization of electrons tunneling from an Fe electrode through ultrathin ferroelectric BaTiO3 (BTO) tunnel barriers (Fig. 1A). The BTO polarization can be electrically switched to point toward oraway from the Fe electrode. We used a half-metallic La0.67Sr0.33MnO3(LSMO) (25) bottom electrode as a spin detector in these artificial multiferroic tunnel junctions (26, 27). Magnetotransport experiments provide evidence for a large and reversible dependence of the TMR on ferroelectric polarization direction.Fig. 1(A) Sketch of the nanojunction defined by electrically controlled nanoindentation. A thin resist is spin-coated on the BTO(1 nm)/LSMO(30 nm) bilayer. The nanoindentation is performed with a conductive-tip atomic force microscope, and the resultingnano-hole is filled by sputter-depositing Au/CoO/Co/Fe. (B) (Top) PFM phase image of a BTO(1 nm)/LSMO(30 nm) bilayer after poling the BTO along 1-by-4–μm stripes with either a negative or positive (tip-LSMO) voltage. (Bottom) CTAFM image of an unpoled area of a BTO(1 nm)/LSMO(30 nm) bilayer. Ω, ohms. (C) X-ray absorption spectra collected at room temperature close to the Fe L3,2 (top), Ba M5,4 (middle), and TiL3,2 (bottom) edges on an AlO x(1.5 nm)/Al(1.5 nm)/Fe(2 nm)/BTO(1 nm)/LSMO(30 nm)//NGO(001) heterostructure. (D) HRTEM and (E) HAADF images of the Fe/BTO interface in a Ta(5 nm)/Fe(18 nm)/BTO(50 nm)/LSMO(30 nm)//NGO(001) heterostructure. The white arrowheads in (D) indicate the lattice fringes of {011} planes in the iron layer. [110] and [001] indicate pseudotetragonal crystallographic axes of the BTO perovskite.The tunnel junctions that we used in this study are based on BTO(1 nm)/LSMO(30 nm) bilayers grown epitaxially onto (001)-oriented NdGaO3 (NGO) single-crystal substrates (28). The large (~180°) and stable piezoresponse force microscopy (PFM) phase contrast (28) between negatively and positively poled areas (Fig. 1B, top) indicates that the ultrathin BTO films are ferroelectric at room temperature (29). The persistence of ferroelectricity for such ultrathin films of BTO arises from the large lattice mismatch with the NGO substrate (–3.2%), which is expected to dramatically enhance ferroelectric properties in this highly strained BTO (30). The local topographical and transport properties of the BTO(1 nm)/LSMO(30 nm) bilayers were characterized by conductive-tip atomic force microscopy (CTAFM) (28). The surface is very smooth with terraces separated by one-unit-cell–high steps, visible in both the topography (29) and resistance mappings (Fig. 1B, bottom). No anomalies in the CTAFM data were observed over lateral distances on the micrometer scale.We defined tunnel junctions from these bilayers by a lithographic technique based on CTAFM (28, 31). Top electrical contacts of diameter ~10 to 30 nm can be patterned by this nanofabrication process. The subsequent sputter deposition of a 5-nm-thick Fe layer, capped by a Au(100 nm)/CoO(3.5 nm)/Co(11.5 nm) stack to increase coercivity, defined a set of nanojunctions (Fig. 1A). The same Au/CoO/Co/Fe stack was deposited on another BTO(1 nm)/LSMO(30 nm) sample for magnetic measurements. Additionally, a Ta(5 nm)/Fe(18 nm)/BTO(50 nm)/LSMO(30 nm) sample and a AlO x(1.5 nm)/Al(1.5nm)/Fe(2 nm)/BTO(1 nm)/LSMO(30 nm) sample were realized for structural and spectroscopic characterizations.We used both a conventional high-resolution transmission electron microscope (HRTEM) and the NION UltraSTEM 100 scanning transmission electron microscope (STEM) to investigate the Fe/BTO interface properties of the Ta/Fe/BTO/LSMO sample. The epitaxial growth of the BTO/LSMO bilayer on the NGO substrate was confirmed by HRTEM and high-resolution STEM images. The low-resolution, high-angle annular dark field (HAADF) image of the entire heterostructure shows the sharpness of theLSMO/BTO interface over the studied area (Fig. 1E, top). Figure 1D reveals a smooth interface between the BTO and the Fe layers. Whereas the BTO film is epitaxially grown on top of LSMO, the Fe layer consists of textured nanocrystallites. From the in-plane (a) and out-of-plane (c) lattice parameters in the tetragonal BTO layer, we infer that c/a = 1.016 ± 0.008, in good agreement with the value of 1.013 found with the use of x-ray diffraction (29). The interplanar distances for selected crystallites in the Fe layer [i.e.,~2.03 Å (Fig. 1D, white arrowheads)] are consistent with the {011} planes ofbody-centered cubic (bcc) Fe.We investigated the BTO/Fe interface region more closely in the HAADF mode of the STEM (Fig. 1E, bottom). On the BTO side, the atomically resolved HAADF image allows the distinction of atomic columns where the perovskite A-site atoms (Ba) appear as brighter spots. Lattice fringes with the characteristic {100} interplanar distances of bcc Fe (~2.86 Å) can be distinguished on the opposite side. Subtle structural, chemical, and/or electronic modifications may be expected to occur at the interfacial boundarybetween the BTO perovskite-type structure and the Fe layer. These effects may lead to interdiffusion of Fe, Ba, and O atoms over less than 1 nm, or the local modification of the Fe DOS close to E F, consistent with ab initio calculations of the BTO/Fe interface (18–20).To characterize the oxidation state of Fe, we performed x-ray absorption spectroscopy (XAS) measurements on a AlO x(1.5 nm)/Al(1.5 nm)/Fe(2 nm)/BTO(1 nm)/LSMO(30 nm) sample (28). The probe depth was at least 7 nm, as indicated by the finite XAS intensity at the La M4,5 edge (28), so that the entire Fe thickness contributed substantially to the signal. As shown in Fig. 1C (top), the spectrum at the Fe L2,3 edge corresponds to that of metallic Fe (32). The XAS spectrum obtained at the Ba M4,5 edge (Fig. 1C, middle) is similar to that reported for Ba2+ in (33). Despite the poor signal-to-noise ratio, the Ti L2,3 edge spectrum (Fig. C, bottom) shows the typical signature expected for a valence close to 4+ (34). From the XAS, HRTEM, and STEM analyses, we conclude that theFe/BTO interface is smooth with no detectable oxidation of the Fe layer within a limit of less than 1 nm.After cooling in a magnetic field of 5 kOe aligned along the [110] easy axis of pseudocubic LSMO (which is parallel to the orthorhombic [100] axis of NGO), we characterized the transport properties of the junctions at low temperature (4.2K). Figure 2A (middle) shows a typical resistance–versus–magnetic field R(H) cycle recorded at a bias voltage of –2 mV (positive bias corresponds to electrons tunneling from Fe to LSMO). The bottom panel of Fig. 2A shows the magnetic hysteresisloop m(H) of a similar unpatterned sample measured with superconducting quantuminterference device (SQUID) magnetometry. When we decreased the magnetic field from a large positive value, the resistance dropped in the –50 to –250 Oe range and then followed a plateau down to –800 Oe, after which it sharply returned to thehigh-resistance state. We observed a similar response when cycling the field back to large positive values. A comparison with the m(H) loop indicates that the switching fields in R(H) correspond to changes in the relative magnetic configuration of the LSMO and Fe electrodes from parallel (at high field) to antiparallel (at low field). The magnetically softer LSMO layer switched at lower fields (50 to 250 Oe) compared with the Fe layer, for which coupling to the exchange-biased Co/CoO induces larger and asymmetric coercive fields (–800 Oe, 300 Oe). The observed R(H) corresponds to a negative TMR = (R ap–R p)/R ap of –17% [R p and R ap are the resistance in the parallel (p) and antiparallel (ap) magnetic configurations, respectively; see the sketches in Fig. 2A]. Within the simple Jullière model of TMR (23) and considering the large positive spin polarization of half-metallic LSMO (25), this negative TMR corresponds to a negative spin polarization for bcc Fe at the interface with BTO, in agreement with ab initio calculations (18–20).Fig. 2(A) (Top) Device schematic with black arrows to indicate magnetizations. p, parallel; ap, antiparallel. (Middle) R(H) recorded at –2 mV and 4.2 K showing negative TMR. (Bottom) m(H) recorded at 30 K with a SQUID magnetometer. emu, electromagnetic units. (B) (Top) Device schematic with arrows to indicate ferroelectric polarization. (Bottom) I(V DC) curves recorded at 4.2 K after poling the ferroelectric down (orange curve) or up (brown curve). The bias dependence of the TER is shown in the inset.As predicted (35–38) and demonstrated (29) previously, the tunnel current across a ferroelectric barrier depends on the direction of the ferroelectric polarization. We also observed this effect in our Fe/BTO/LSMO junctions. As can be seen in Fig. 2B, after poling the BTO at 4.2 K to orient its polarization toward LSMO or Fe (with a poling voltage of VP–≈ –1 V or VP+≈ 1 V, respectively; see Fig. 2B sketches),current-versus-voltage I(V DC) curves collected at low bias voltages showed a finite difference corresponding to a tunnel electroresistance as large as TER = (I VP+–I VP–)/I VP–≈ 37% (Fig. 2B, inset). This TER can be interpreted within an electrostatic model (36–39), taking into account the asymmetric deformation of the barrier potential profile that is created by the incomplete screening of polarization charges by different Thomas-Fermi screening lengths at Fe/BTO and LSMO/BTO interfaces.Piezoelectric-related TER effects (35, 38) can be neglected as the piezoelectric coefficient estimated from PFM experiments is too small in our clamped films (29). TER measurements performed on a BTO(1 nm)/LSMO(30 nm) bilayer with the use of a CTAFM boron-doped diamond tip as the top electrode showed values of ~200%(29). Given the strong sensitivity of the TER on barrier parameters and barrier-electrode interfaces, these two values are not expected to match precisely. We anticipate that the TER variation between Fe/BTO/LSMO junctions and CTAFM-based measurements is primarily the result of different electrostatic boundary conditions.Switching the ferroelectric polarization of a tunnel barrier with voltage pulses is also expected to affect the spin-dependent DOS of electrodes at a ferromagnet/ferroelectric interface. Interfacial modifications of the spin-dependent DOS of the half-metallic LSMO by the ferroelectric BTO are not likely, as no states are present for the minority spins up to ~350 meV above E F (40, 41). For 3d ferromagnets such as Fe, large modifications of the spin-dependent DOS are expected, as charge transfer between spin-polarized empty and filled states is possible. For the Fe/BTO interface, large changes have been predicted through ab initio calculations of 3d electronic states of bcc Fe at the interface with BTO by several groups (18–20).To experimentally probe possible changes in the spin polarization of the Fe/BTO interface, we measured R(H) at a fixed bias voltage of –50 mV after aligning the ferroelectric polarization of BTO toward Fe or LSMO. R(H) cycles were collected for each direction of the ferroelectric polarization for two typical tunnel junctions of the same sample (Fig. 3, B and C, for junction #1; Fig. 3, D and E, for junction #2). In both junctions at the saturating magnetic field, high- and low-resistance states are observed when the ferroelectric polarization points toward LSMO or Fe, respectively, with a variation of ~ 25%. This result confirms the TER observations in Fig. 2B.Fig. 3(A) Sketch of the electrical control of spin polarization at the Fe/BTO interface.(B and C) R(H) curves for junction #1 (V DC = –50 mV, T = 4.2 K) after poling the ferroelectric barrier down or up, respectively. (D and E) R(H) curves for junction #2 (V DC = –50 mV, T= 4.2 K) after poling the ferroelectric barrier down or up, respectively.More interestingly, here, the TMR is dramatically modified by the reversal of BTO polarization. For junction #1, the TMR amplitude changes from –17 to –3% when the ferroelectric polarization is aligned toward Fe or LSMO, respectively (Fig. 3, B and C). Similarly for junction #2, the TMR changes from –45 to –19%. Similar results were obtained on Fe/BTO (1.2 nm)/LSMO junctions (28). Within the Jullière model (23), these changes in TMR correspond to a large (or small) spin polarization at the Fe/BTO interface when the ferroelectric polarization of BTO points toward (or away from) the Fe electrode. These experimental data support our interpretation regarding the electrical manipulation of the spin polarization of the Fe/BTO interface by switching the ferroelectric polarization of the tunnel barrier.To quantify the sensitivity of the TMR with the ferroelectric polarization, we define a term, the tunnel electromagnetoresistance, as TEMR = (TMR VP+–TMR VP–)/TMR VP–. Largevalues for the TEMR are found for junctions #1 (450%) and #2 (140%), respectively. This electrical control of the TMR with the ferroelectric polarization is repeatable, as shown in Fig. 4 for junction #1 where TMR curves are recorded after poling the ferroelectric up, down, up, and down, sequentially (28).Fig. 4TMR(H) curves recorded for junction #1 (V DC = –50 mV, T = 4.2 K) after poling the ferroelectric up (VP+), down (VP–), up (VP+), and down (VP–).For tunnel junctions with a ferroelectric barrier and dissimilar ferromagnetic electrodes, we have reported the influence of the electrically controlled ferroelectric barrier polarization on the tunnel-current spin polarization. This electrical influence over magnetic degrees of freedom represents a new and interfacial magnetoelectric effect that is large because spin-dependent tunneling is very sensitive to interfacial details. Ferroelectrics can provide a local, reversible, nonvolatile, and potentially low-power means of electrically addressing spintronics devices.Supporting Online Material/cgi/content/full/science.1184028/DC1Materials and MethodsFigs. S1 to S5References∙Received for publication 30 October 2009.∙Accepted for publication 4 January 2010.References and Notes1. C. Chappert, A. Fert, F. N. Van Dau, The emergence of spin electronics indata storage. Nat. Mater. 6,813 (2007).2.I. Žutić, J. Fabian, S. Das Sarma, Spintronics: Fundamentals andapplications. Rev. Mod. Phys. 76,323 (2004).3.J. C. Slonczewski, Current-driven excitation of magnetic multilayers. J.Magn. Magn. Mater. 159, L1(1996).4.J. Nitta, T. Akazaki, H. Takayanagi, T. Enoki, Gate control of spin-orbit interaction in an inverted In0.53Ga0.47As/In0.52Al0.48Asheterostructure. Phys. Rev. Lett. 78, 1335 (1997).5.H. Ohno et al., Electric-field control offerromagnetism. Nature 408, 944 (2000).6. D. Chiba et al., Magnetization vector manipulation by electricfields. Nature 455, 515 (2008).7.M. Weisheit et al., Electric field–induced modification of magnetism inthin-film ferromagnets. Science315, 349 (2007).8.T. Maruyama et al., Large voltage-induced magnetic anisotropy changein a few atomic layers of iron.Nat. Nanotechnol. 4, 158 2009).9.S. W. E. Riester et al., Toward a low-voltage multiferroic transistor:Magnetic (Ga,Mn)As under ferroelectric control. Appl. Phys.Lett. 94, 063504 (2009).10.I. Stolichnov et al., Non-volatile ferroelectric control of ferromagnetismin (Ga,Mn)As. Nat. Mater. 7, 464(2008).11. C. Bihler et al., Ga1−x Mn x As/piezoelectric actuator hybrids: A modelsystem for magnetoelastic magnetization manipulation. Phys. Rev.B 78, 045203 (2008).12.M. Overby, A. Chernyshov, L. P. Rokhinson, X. Liu, J. K. Furdyna, GaMnAs-based hybrid multiferroic memory device. Appl. Phys.Lett. 92, 192501 (2008).13. C. Thiele, K. Dörr, O. Bilani, J. Rödel, L. Schultz, Influence of strain on themagnetization and magnetoelectric effect inLa0.7A0.3MnO3∕PMN-PT(001)(A=Sr,Ca). Phys.Rev.B 75, 054408 (2007).14.W. Eerenstein, M. Wiora, J. L. Prieto, J. F. Scott, N. D. Mathur, Giantsharp and persistent converse magnetoelectric effects in multiferroic epitaxial heterostructures. Nat. Mater. 6, 348 (2007).15.T. Kanki, H. Tanaka, T. Kawai, Electric control of room temperatureferromagnetism in a Pb(Zr0.2Ti0.8)O3/La0.85Ba0.15MnO3 field-effect transistor. Appl.Phys. Lett. 89, 242506 (2006).16.Y.-H. Chu et al., Electric-field control of local ferromagnetism using amagnetoelectric multiferroic. Nat. Mater. 7, 478 2008).17.S. Sahoo et al., Ferroelectric control of magnetism in BaTiO3∕Feheterostructures via interface strain coupling. Phys. Rev. B 76, 092108 (2007). 18. C.-G. Duan, S. S. Jaswal, E. Y. Tsymbal, Predicted magnetoelectric effectin Fe/BaTiO3 multilayers: Ferroelectric control of magnetism. Phys. Rev.Lett. 97, 047201 (2006).19.M. Fechner et al., Magnetic phase transition in two-phase multiferroicspredicted from first principles.Phys. Rev. B 78, 212406 (2008).20.J. Lee, N. Sai, T. Cai, Q. Niu, A. A. Demkov, preprint availableat /abs/0912.3492v1.21.K. Yamauchi, B. Sanyal, S. Picozzi, Interface effects at ahalf-metal/ferroelectric junction. Appl. Phys. Lett. 91, 062506 (2007).22.M. K. Niranjan, J. P. Velev, C.-G. Duan, S. S. Jaswal, E. Y. Tsymbal, Magnetoelectric effect at the Fe3O4/BaTiO3 (001) interface: A first-principles study. Phys. Rev. B 78, 104405 (2008).23.M. Jullière, Tunneling between ferromagnetic films. Phys. Lett.A 54, 225 (1975).24.J. F. Scott, Applications of modern ferroelectrics. Science 315, 954 (2007).25.M. Bowen et al., Nearly total spin polarization in La2/3Sr1/3MnO3 fromtunneling experiments. Appl. Phys. Lett. 82, 233 (2003).26.J. P. Velev et al., Magnetic tunnel junctions with ferroelectric barriers:Prediction of four resistance states from first principles. Nano Lett. 9, 427 (2009).27. F. Yang et al., Eight logic states of tunneling magnetoelectroresistancein multiferroic tunnel junctions.J. Appl. Phys. 102, 044504 (2007).28.Materials and methods are available as supporting materialon Science Online.29.V. Garcia et al., Giant tunnel electroresistance for non-destructivereadout of ferroelectric states. Nature460, 81 (2009).30.K. J. Choi et al., Enhancement of ferroelectricity in strained BaTiO3 thinfilms. Science 306, 1005(2004).31.K. Bouzehouane et al., Nanolithography based on real-time electricallycontrolled indentation with an atomic force microscope for nanocontactelaboration. Nano Lett. 3, 1599 (2003).32.T. J. Regan et al., Chemical effects at metal/oxide interfaces studied byx-ray-absorption spectroscopy.Phys. Rev. B 64, 214422 (2001).33.N. Hollmann et al., Electronic and magnetic properties of the kagomesystems YBaCo4O7 and YBaCo3M O7 (M=Al, Fe). Phys. Rev. B 80, 085111 (2009).34.M. Abbate et al., Soft-x-ray-absorption studies of the location of extracharges induced by substitution in controlled-valence materials. Phys. Rev.B 44, 5419 (1991).35. E. Y. Tsymbal, H. Kohlstedt, Tunneling across aferroelectric. Science 313, 181 (2006).36.M. Ye. Zhuravlev, R. F. Sabirianov, S. S. Jaswal, E. Y. Tsymbal, Giantelectroresistance in ferroelectric tunnel junctions. Phys. Rev.Lett. 94, 246802 (2005).37.M. Ye. Zhuravlev, R. F. Sabirianov, S. S. Jaswal, E. Y. Tsymbal, Erratum:Giant electroresistance in ferroelectric tunnel junctions. Phys. Rev.Lett. 102, 169901 2009).38.H. Kohlstedt, N. A. Pertsev, J. Rodriguez Contreras, R. Waser, Theoreticalcurrent-voltage characteristics of ferroelectric tunnel junctions. Phys. Rev.B 72, 125341 (2005).39.M. Gajek et al., Tunnel junctions with multiferroic barriers. Nat.Mater. 6, 296 (2007).40.M. Bowen et al., Spin-polarized tunneling spectroscopy in tunneljunctions with half-metallic electrodes.Phys. Rev. Lett. 95, 137203 (2005).41.J. D. Burton, E. Y. Tsymbal, Prediction of electrically induced magneticreconstruction at the manganite/ferroelectric interface. Phys. Rev.B 80, 174406 (2009).42.We thank R. Guillemet, C. Israel, M. E. Vickers, R. Mattana, J.-M. George,and P. Seneor for technical assistance, and C. Colliex for fruitful discussions on the microscopy measurements. This study was partially supported by theFrance-U.K. Partenariat Hubert Curien Alliance program, the French RéseauThématique de Recherche Avancée Triangle de la Physique, the European Union (EU) Specific Targeted Research Project (STRep) Manipulating the Coupling inMultiferroic Films, EU STReP Controlling Mesoscopic Phase Separation, U.K. Engineering and Physical Sciences Research Council grant EP/E026206/I, French C-Nano Île de France, French Agence Nationale de la Recherche (ANR) Oxitronics, French ANR Alicante, the European Enabling Science and Technology through European Elelctron Microscopy program, and the French Microscopie Electronique et Sonde Atomique network. X.M.acknowledges support from Comissionat per a Universitats i Recerca (Generalitat de Catalunya).。
英文实验报告
英文实验报告Experimental Report。
Introduction。
The purpose of this experiment was to investigate the effects of different temperatures on the rate of enzyme activity. Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are sensitive to changes in temperature, and this experiment aimed to explore how temperature affects the activity of the enzyme catalase.Materials and Methods。
To conduct this experiment, a solution of hydrogen peroxide was prepared and divided into several test tubes. Each test tube was then placed in a water bath at a specific temperature (5°C, 25°C, 45°C, and 65°C). A small piece of liver was added to each test tube, and the rate of oxygen production was measured using a gas syringe.Results。
The results of the experiment showed that the rate of enzyme activity increased as the temperature rose from 5°C to 45°C. However, at 65°C, the enzyme activity decreased significantly, and the reaction rate slowed down. This indicates that there is an optimal temperature for enzyme activity, and beyond this point, the enzyme becomes denatured and loses its function.Discussion。
物理实验报告英文版7
iv
Table of Contents
Title Page Authorization Page Signature Page Acknowledgements Table of Contents List of Figures List of Tables Abstract Chapter1 Introduction 1.1 Structure of Carbon Nanotubes . . . . . . . . . . . . . . . . . . . . 1.2 Electronic properties of Carbon Nanotubes . . . . . . . . . . . . . . Chapter2 Superconductivity in 0.4nm Carbon Nanotubes array 2.1 The band structure of 0.4nm Carbon Nanotubes . . . . . . . . . . 2.2 Meissner effect in 0.4nm Carbon Nanotubes array . . . . . . . . . 2.3 The model of coupled one-dimensional superconducting wires . . . 2.4 Motivation and scope of the thesis . . . . . . . . . . . . . . . . . . i ii iii iv v vii xi xii 1 3 4 8 9 9 12 13
July 2008, Hong Kong
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简单的英语实验报告
简单的英语实验报告Title: Simple English Experiment ReportIntroductionIn this experiment, we aimed to test the effects of different types of fertilizer on plant growth. We hypothesized that plants treated with organic fertilizer would grow taller and healthier compared to those treated with chemical fertilizer. Materials and MethodsWe selected 20 pots and filled them with equal amounts of soil. We then planted the same type of seeds in each pot. Ten pots were treated with organic fertilizer, while the other ten were treated with chemical fertilizer. We watered the plants regularly and measured their height and health status every week for a period of one month.ResultsAfter one month, we observed that the plants treated with organic fertilizer grew taller and appeared healthier compared to those treated with chemical fertilizer. The organic fertilizer seemed to provide better nutrients for the plants, resulting in stronger and more vibrant growth.DiscussionOur results support our hypothesis that organic fertilizer is more beneficial for plant growth compared to chemical fertilizer. This could be due to the natural nutrients present in organic fertilizer, which may be more easily absorbed by plants. Further research could explore the specific nutrients present in each typeof fertilizer and their effects on plant growth.ConclusionIn conclusion, our experiment demonstrates the positive effects of organic fertilizer on plant growth. This information could be valuable for farmers and gardeners looking to maximize the health and productivity of their plants.。
大学物理实验 4-2实验报告(英文版)
1 0.0512 0.0511
2 0.0511 0.0510
3 0.0513 0.0512
4 0.0512 0.0511
5 0.0515 0.0514
6 0.0513 0.0512
������0 = 0.0001������������ ������������������ =0.0512cm Data analysis: 1.������������ = ������ 2 + ∆2 ������������ = 0.004������������ 2.������������ = 1������������������������ = 5������������������������ = 0.02������������ ������������������ ± ������������ =0.512±0.004mm L± ������������ =83.25±0.5cm D± ������������ = 298.72 ± 1cm l± ������������ = 7.55 ± 0.02cm 3.
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can be known by counting the number of the weights. L can be measuredby the tape; A can be counted by using the microcalliper.∆L is too small to measure directly, we must use the Elastic modulus instrument. Light lever principle is used to measurethe small change amplification. By using reflector we can make the small length change big, in the end, we get E=8DLmg/π������ 2 l(X-������0 ). D is the distance between the reflector and the ruler, l is the length of light leverage. L is the primitive length of the steel, d is the radius of it. Procedure: 1. Adjusting instrument device Adjusting the reflector and then we can see the ruler through the telescope. Adjusting the telescope so that we can see the scale on the ruler clearly. 2. Put eight weights on the hook; write down the X on the ruler
写一份简单的实验报告英语作文
写一份简单的实验报告英语作文Experimental Report。
Introduction:The purpose of this experiment was to investigate the effect of temperature on the rate of enzyme activity. Enzymes are biological catalysts that speed up chemical reactions in living organisms. The rate of enzyme activity is influenced by various factors, including temperature. Understanding the relationship between temperature and enzyme activity is important in fields such as medicine and biochemistry.Materials and Methods:1. Materials:Amylase enzyme solution。
Starch solution。
Test tubes。
Thermometer。
Water bath。
Iodine solution。
Stopwatches。
2. Procedure:1. Label six test tubes as A, B, C, D, E, and F.2. Add 2 mL of amylase enzyme solution to each test tube.3. Place test tubes A, B, and C in a water bath at 10°C, test tubes D and E at 30°C, and test tube F at 50°C.4. Add 2 mL of starch solution to each test tube.5. Start the stopwatch and mix the contents of each test tube gently.6. At 30-second intervals, remove a drop of the mixture from each test tube and place it on a white tile.7. Add a drop of iodine solution to each drop of the mixture on the white tile.8. Observe the color change. A blue-black color indicates the presence of starch, while a yellow-brown color indicates the absence of starch.9. Record the time taken for the color change to occur in each test tube.10. Repeat the experiment three times for each temperature.Results:The following table shows the time taken for the color change to occur in each test tube:Test Tube Temperature (°C) Time for Color Change (seconds)。
大学物理实验报告英文版--全息照相
physical lab report:HolographyWriter:[Backgrounds]Lights are electromagnetic waves.A monochromatic optical wave can be mathematically expressed as a waveequation:2cos()r x A tπωφλ=+-where A is the amplitude and)2(λπϕωrt-+carries phase information. The way we viewany given object is to observe the brightness (amplitude), color (wavelength), and shape/distance (phase).A conventional photograph records the focused image of an object on a photographic film or plate. A hologram is a photographic recording of an optical interference pattern. The amplitude and phase of light coming from the object are stored in the hologram. The phase information enables us to reconstruct the original wavefront and hence obtain a three-dimensional image in space.The holography you experience in this lab will consist of two steps, a) recording: the amplitude and phase information of an object is recorded on a film, b) viewing: illuminating the film to reconstruct the object that was being filmed.This experiment uses a 658nm diode laser as a source of coherent light which irradiates the objects, and also provides a reference beam of uniform amplitude and phase. [Process]1.RecordingAt the very beginning,we prepare light path according to Fig. First,we have a dark environment .Then we adjust the path length of the reference and object beam, so that the path difference is small. Then,we adjust the devices so that both the object and reference beams are irradiating the film area uniformly.Teacher told us that the ratio between the object and reference beams should better be between 1:1 to 1:10. Then my partner keep adjusting the optics till these conditions are met. Successfully we get an optical film (wrapped in black paper) and mount it onto the holder. Then ,we expose the film to light for about 0.5 second, then dismount the film.Figure 1: recording of a hologram2.Film developmentAfter getting a film,we take it to the dark room to develop. There are three bath basins: developer, stop bath (water), and fixer. According to the instructor, we immerse the film into development liquid. My partner flip the film up and down with the tweezers and we wait till the gray-scale is similar to the color on the bottom of the basin. This usually takes 2 minutes and 25 seconds.Later,we rinse the film in the water basin for 25 seconds, and we take it to the fixer. I immerse it in the fixer for 3 minutes. We take the film to the viewing room and dry the film.3.ViewingThe principle to reconstruct image from a hologram is via light diffraction. If a laser beam irradiates onto the film exactly like the object beam, diffraction will happen on the pattern recorded on the hologram. See figure below.Figure 2: illustration of image reconstruction in hologram..We are all excited to get ready to view the film. Before viewing, we have a high expectation about it.We Use a viewing beam to irradiate the film. After having made sure the emulsion side is facing the beam, we adjust our viewing angle on the other side of the film to observe an expected 3-D image of the object.HOWEVER unfortunately,we are unlucky to find the image.No matter what angle we try,we can’t find it.We suppose it is because the angle is too large to find.So we try once again,LUCKLY,we finally find the 3-D image! -------A lovely white horse!![Feeling]In this experiment,we have a deep impression of the 3-D image. I think this experience is very unforgettable.In deed,this is where physics is attractive to us.。
简单的实验报告英语作文
简单的实验报告英语作文Experimental Report: The Effect of Temperature on the Rate of Enzyme Activity。
Introduction。
Enzymes are proteins that catalyze biochemicalreactions in living organisms. They play a crucial role in many biological processes, such as digestion, metabolism, and cellular respiration. Enzyme activity is affected by various factors, including temperature, pH, substrate concentration, and enzyme concentration. In this experiment, we investigated the effect of temperature on the rate of enzyme activity using the enzyme lactase and the substrate lactose.Materials and Methods。
Materials:Lactase solution。
Lactose solution。
Test tubes。
Thermometer。
Water bath。
Timer。
Spectrophotometer。
Methods:1. Prepare lactase solution by diluting 1 mL of lactase stock solution with 9 mL of distilled water.2. Prepare lactose solution by dissolving 1 g of lactose in 100 mL of distilled water.3. Label six test tubes as follows: 0°C, 20°C, 30°C, 40°C, 50°C, and 60°C.4. Add 2 mL of lactase solution to each test tube.5. Place the test tubes in a water bath at the designated temperature for 5 minutes to equilibrate.6. Add 2 mL of lactose solution to each test tube and start the timer.7. Mix the contents of each test tube by gently swirling.8. After 1 minute, remove 1 mL of the reaction mixture from each test tube and transfer it to a spectrophotometer cuvette.9. Measure the absorbance of each sample at 540 nm using a spectrophotometer.10. Repeat steps 8-9 every minute for 5 minutes.11. Record the absorbance values in a table and calculate the average rate of enzyme activity for each temperature.Results。
实验报告英文版
实验报告英文版Experiment ReportThe purpose of this experiment was to investigate the influence that various temperature levels have on the reaction rate of a chemical reaction. The experiment was conducted in a laboratory and seven different temperatures were tested, ranging from 20°C to 90°C.The reaction was carried out using a beaker filled with 100ml of water and 20ml of a solution containing 0.01 mol/L sodium thiosulphate. 10ml of 1 mol/L hydrochloric acid was added to the beaker and the time it took for the reaction to take place was then measured.The results of the experiment indicated that the higher the temperature of the reaction, the shorter the time it took for the reaction to take place. For example, when the reaction took place at 20°C, the time taken was 13 minutes and 37 seconds, whereas when it took place at 90°C, the time taken was only 2 minutes and 47 seconds.These results demonstrate that increasing the temperature of a chemical reaction will lead to an increase in the rate at which the reaction takes place. This is due to the fact that the molecules present in the reaction are moving faster and therefore are able to collide more frequently and with greater force.Overall, the experiment showed that the rate of a chemical reaction can be affected significantly by changing the temperature at which the reaction takes place. Increasingthe temperature can lead to a significant decrease in the time it takes for a reaction to take place.。
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Ruby Tan
Partner: Kathryn Zhu
04/19/12
LAB#24SL:Musical Intervals
Objective:
To determine the frequency ratios for common musical intervals. Procedure:
Come into the lab, open DataStudio, switch on the interface, select Create Experiment, then Sound Creator. Change simultaneous tones to 2. Then put on the headphone to listen the voice, changing the wave of a sound to a longer wave(lower tones). Hum the indicated for a specified interval and find the pitch for the 2nd note. Do it for 5 times with 5 different songs.
Ruby Tan
Partner: Kathryn Zhu
09/29/11
LAB#24SL:Musical Intervals
Conclusion
In this lab, we know the wave of the songs concern with the tones of it. Shorter period waves have a lower tones. Amplitude cause the loudness of the songs. This lab is good for us to analyze the notes of all the songs.
Kathryn Zhu
Partner: Ruby Tan
04/19/2012
LAB#24SL:Musical Intervals
Objective
To determine the frequency ratios for common musical intervals. Procedure
First, start Datastudio,choose Create Experiment, then Sound Creator. Then, Change simultaneous tones to 2. Next, put the headphone on and started to find our voice tones. Next, hum 5 songs in key:C,D,E,F,G. Finish the 5 songs and finally, record the data in calculation table.
Kathryn Zhu
Partner: Ruby Tan
04/19/2012
LAB#24SL:Musical Intervals
Conclusion
This lab is about sounds. I am very appreciated that our school have these devices to let us to test voices by myself. To measure the sound of mine is difficult because when i was on the headphone, I couldn't hear my voice clearly. Finally I change the length of the voice on the computer to a high key then fix the problem.
Beckman Zhuang
Partner: Christian
19/04/12
LAB#24SL:Musical Intervals
Objective
To determine the frequency ratios for common musical intervals. Procedure
Enter the lab room and switch on the computer, then open the DataStudios and set up Create Experiment, Sound Creator, and change simultaneous Tab to 2 and choose Period view. Then change the Amplitude handle and wavelength to a perfect place. Then start to hum the songs that require, try to use some different key to measure what cause the sound changed. Finally, write down the data and clean the area.
Beckman Zhuang
Partner: Christian
19/04/12
LAB#24SL:Musical Intervals
Conclusion
During this lab, I found many things amazed me, such as the C key have a very similar but not exactly same wavelength with D key. I try moving the A wavelength to 2 times as B wave, but it make a strange noise. I need to
figure it out in the class.。