Magnetoelectric Films Research Articles

Enhancing osteogenic differentiation of BMSCs on high magnetoelectric response films.

High performance of biomaterial surfaces provides a sound basis to mediate cellular growth behavior. In this work, we attempted to incorporate both positive and negative magnetostriction particles of CoFe2O4 (CFO) and TbxDy1-xFe2 alloy (TD) into piezoelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) for forming high magnetoelectric effect films, on which osteogenic differentiation could be dynamically mediated by a magnetic-field-induced surface potential (φME).The negatively poled film with TD/CFO volume ratio of 1:4 (1T4C) showed a highest magnetoelectric effect with φME of -171mV at 2800Oe. Compared with CFO/P(VDF-TrFE) and TD/P(VDF-TrFE) films, the φME increased about 213% and 173%, respectively. This could result from that P(VDF-TrFE) dipole domains receive a larger off-axial stress caused by the distribution characteristic of CFO and TD in P(VDF-TrFE), consequently to facilitate P(VDF-TrFE) dipole domain rearrangement. When MSCs were cultured on 1T4C film for 7 or 14days, the magnetic actuation was setup to begin at the 4th or 8th day after the culture. The 7-day osteogenic differentiation was hardly affected for magnetic actuation at 4th day, moreover, the 14-day differentiation was significantly enhanced for magnetic actuation at 8th day. The enhancement appears just at a relatively late period of the cell growth, probably because the cells need a steady change in cell membrane potential to disassociate pairs of β-catenin and E-cadherin and activate osteogenic-related signaling pathway. This work could provide an alternative way to promote performance for magnetoelectric materials, and get insight into understanding of interactions of surface potential with cells.

Enhanced magnetoelectric coefficient and interfacial compatibility by constructing a three-phase CFO@BT@PDA/P(VDF-TrFE) core-shell nanocomposite

A ferroelectric ceramic barium titanate (BaTiO3, BT) layer and an interfacial agent polydopamine (PDA) as the shells are coated on the cobalt ferrite (CoFe2O4, CFO) nanoparticles successively to fabricate the interfacial compatibility of this magnetic oxide. Subsequently, the coated nanoparticles are compounded with ferroelectric poly(vinylidene fluoride-trifluoro ethylene) (P(VDF-TrFE)) matrix to obtain the CFO@BT@PDA/(P(VDF-TrFE) magnetoelectric nanocomposite films. We find these nanocomposites with three phases including a CFO magnetic core, a BT piezoelectric shell and the P(VDF-TrFE) piezoelectric matrix show a considerable dielectric permittivity of 85.7 and a maximum polarization of 49.5 μC/cm2. Attractively, after poling the saturated magnetization of this film increases from 52.1 emu/g to 61.7 emu/g, corresponding to a significant magnetoelectric effect. Through non self-consistent theory (NSC), the magnetoelectric coupling coefficient (αE33) of CFO@BT@PDA/(P(VDF-TrFE) film is calculated to reach 150.58 mV/cm·Oe, indicating that this flexible multiferroic film has a prospect of application on energy collector or new information storage devices.

Magnetoelectricity of barium titanate/cobalt ferrite nanoparticles incorporated into poly(vinylidene fluoride-co-trifluoroethylene) copolymer films

Incorporating ferroelectric and ferromagnetic nanoparticles into copolymers can produce composites with novel properties for broad applications especially in electronics. In this research, nanoparticles of barium titanate (BTO) and cobalt iron oxide (CFO) were chemically synthesised and then individually incorporated in poly(vinylidene fluoride-co-trifluoroethylene) to form multi-layered magnetoelectric film. BTO-P(VDF-TrFE)/CFO-P(VDF-TrFE)/BTO-P(VDF-TrFE) sandwich type films - (20-30 μm in thickness each) - were synthesised using a home-made simple mould casting and blending techniques. The addition of BTO and CFO nanoparticles to the polymer enhanced the dielectric constant, but lowered the ferroelectric-paraelectric phase transition temperature of the P(VDF-TrFE). For the sandwich type film, a maximum value of direct out of plane magnetoelectric coupling coefficient (α33) 145 mV/cm·Oe was measured at ambient temperature. For such structure, the perfect isolating condition of the cobalt ferrite piezomagnetic phase and the proper contact and bonding between the piezoelectric and magnetostrictive phases enhanced the magnetoelectric effect. The fabricated film could be a potential candidate for magnetoelectric devices and sensor applications.

Atomic layer deposition of YMnO3 thin films

YMnO3 (YMO) thin films were synthesized by radical-enhanced atomic layer deposition (RE-ALD) on silicon (Si) and yttria-stabilized zirconia (YSZ)substrates, to investigate the effect of film composition and substrates on their intrinsic magnetic properties. The crystalline phase of these ultra-thin films depends on both the processing conditions and the substrate lattice parameters. The Mn/Y atomic ratio of the YMO thin films could be controlled near unity by adjusting the Mn:Y precursor pulsing ratio during the RE-ALD processes. The ALD YMO thin film on Si (111) was orthorhombic, regardless of the film thickness with a Néel temperature (TN) between 48 ∼ 62 K, as determined through the anomalies observed during DC magnetic susceptibility measurements. However, ultra-thin ALD YMO films (∼6 nm) on YSZ (1 1 1), at a Mn/Y atomic ratio near unity, has both orthorhombic- and hexagonal- phases, yielding two TN anomalies measured at ∼48 K and ∼85 K. The induction of magnetization of ultra-thin YMO film on Si (1 1 1) under an in-situ 20 V electric poling indicates that the magnetoelectric coupling was observed below TN, showing that the ALD synthesis could be a promising technique to deposit ultra-thin magnetoelectric films.

Impact of heat-treatment conditions on ferroelectric, ferromagnetic and magnetoelectric properties of multi-layered composite films of Ba0.9Ca0.1TiO3/CoFe2O4

The magnetoelectric films of Ba0.9Ca0.1TiO3(BCT)/CoFe2O4(CFO) were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel and spin-coating method under three kinds of heat-treatment conditions. It is shown that the heat-treatment conditions have a great effect on the ferroelectric, ferromagnetic and magnetoelectric properties of the composite films. Among the composite films prepared under three kinds of heat-treatment conditions, the composite films prepared under the complete heat-treatment condition (CHC composite films) have the best ferroelectric, ferromagnetic and magnetoelectric properties. They possess largest value of αE (82 mV cm−1 Oe−1). The complete heat-treatment condition is the most appropriate heat-treatment condition for obtaining the best magnetoelectric properties. Ferroelectric phase and ferromagnetic phase can coexist without inter-diffusion at the interface in CHC composite films.

Magnetoelectric response and tunneling magnetoresistance behavior of flexible P(VDF-H FP)/Cobalt ferrite nanofiber composite films

Fabrication of magnetoelectric (ME) polymer composite films by embedding ferromagnetic cobalt ferrite (CoFe2O4) nanofibers into electroactive poly(vinylidene fluoride–hexafluoropropylene) (P(VDF-HFP)) matrix is reported. Single-phase CoFe2O4 nanofibers made of cubic spinel nano crystallites are synthesized by using electro-spinning method, whereas the solution-casting technique is adapted to prepare flexible polymer composite films. The influence of CoFe2O4 nanofiber on structural, functional, magnetic, ferroelectric, and magnetoresistance properties of the composite films is investigated. The cross-coupling between ferroelectric and ferromagnetic orderings is ensured, by the variations of ferroelectric response at different magnetic fields. These magnetoelectric films are found to exhibit a negative tunneling magnetoresistance (TMR) effect with maximum TMR% of 28 for the film with 20 wt% of CoFe2O4 loading. The dielectric constant and electrical energy storage density of the films are increased with the addition of CoFe2O4 nanofiber. The ME films exhibiting TMR and high energy density can be the potential candidates for multifunctional device applications such as memory and spintronics devices, magnetic sensor, and bio-sensor.

Magnetoelectric P(VDF-HFP)-CoFe2O4 films and their giant magnetoresistance properties

Abstract Magnetoelectric (ME) nanocomposite flexible films composed of electroactive poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) and ferromagnetic cobalt ferrite (CoFe2O4) are fabricated. Single-phase nano CoFe2O4 with cubic spinel structure, synthesized by sol-gel auto combustion technique, is reinforced in different weight percentages to fabricate P(VDF-HFP)-CoFe2O4 films through spin coating technique. Effect of CoFe2O4 on structural, morphological, magnetic, ferroelectric, magnetoelectric properties, and giant magnetoresistance (GMR) behavior has been investigated. It is observed that the reinforcement of CoFe2O4 in P(VDF-HFP) matrix has strongly influenced the formation of β-phase conformation and the degree of structural order. The co-existence of ferroelectric and ferromagnetic orderings in the films has been demonstrated by the P-E and M-H plots. The variations in the polarization effects in the presence of a magnetic field provide the evidence for magnetoelectric cross-coupling in P(VDF-HFP)-CoFe2O4. The films exhibit a GMR effect from 7% to 100%. In order to demonstrate the use of ME induced GMR in magnetic field sensing, P(VDF-HFP)-CoFe2O4 film (10 wt%) is used in a prototype sensor circuit. A good sensing ability and linear response obtained prove that the prepared film can be used as field sensor.

Comprehensive Evaluation of Surface Potential Characteristics on Mesenchymal Stem Cells' Osteogenic Differentiation.

The surface electric potential of biomaterials has been extensively proven to play a critical role in stem cells' fate. However, there are ambiguous reports on the relation of stem cells' osteogenic capacity to surface potential characteristics (potential polarity and intensity). To address this, we adopted a surface with a wide potential range and both positive/negative polarity in a comprehensive view to get insight into surface potential-regulating cellular osteogenic differentiation. Tb xDy1- xFe2 alloy/poly(vinylidene fluoride-trifluoroethylene) magnetoelectric films were prepared, and the film could provide controllable surface potential characteristics with positive or negative polarity and potential (ϕME) intensity variation from 0 to ±120 mV as well as keep the surface chemical composition and microstructure unchanged. Cell culture results showed that osteogenic differentiation of mesenchymal stem cells on both positive and negative potential films was obviously upregulated when the /ϕME/ intensities were set from 0-55 mV. Differently, the highest upregulated osteogenic differentiation on the positive potential films corresponded to the /ϕME/ intensity from 35-55 mV and was better than that on the negative potential films whereas the highest on the negative potential films corresponded to the /ϕME/ intensity from 0-35 mV and was better than that on the positive potential films. This fact could illustrate why previous reports appeared ambiguously; i.e., the comparative result in osteogenic differentiation between the positive and negative potential films strongly depends on the selection of surface potential intensity. On the basis of assaying of the exposed functional sites (RGD and PHSRN) of the adsorbed fibronectin (FN) and the expression of cellular integrin α5 and β1 subunits, the difference in the behavior between the positive and negative potential films was attributed to the distinct conformation of adsorbed fibronectin (FN) and the opposite changing trend with /ϕME/ for the two films, which triggers the osteogenesis-related FAK/ERK signaling pathway to a different extent. This study could provide new cognition for the in-depth understanding of the regulation mechanism underlying surface potential characteristics in cell behaviors.

Individually free-standing piezoelectric nanotubes-based BaTiO3/CoFe2O4 magnetoelectric thin films

In this study, individually free-standing piezoelectric nanotubes-based magnetoelectric thin films were synthesized by complexation of one-dimensional (1D) BaTiO3 as the piezoelectric phase, and CoFe2O4 as the magnetostrictive phase. Particularly, the individually TiO2 free-standing nanotubes were developed onto a Ti substrate via metal anodizing to obtain a high standing stability of 1D piezoelectric structure and a filling volume of magnetostrictive phase, simultaneously for fabrication of magnetoelectric thin films. After BaTiO3 perovskite conversion from the TiO2 nanotubes, an enough volume still remains for sufficient self-filling of CoFe2O4 between the BaTiO3 nanotubes. Finally, BaTiO3/CoFe2O4 magnetoelectric films were found to exhibit a dense structure being suitable for strong magnetostriction-mediated piezoelectric voltages. The structure design, based on individually free-standing nanotubes, would be feasible for flexible magnetoelectric devices such as health monitoring sensors, energy harvesters, and memory devices.

Vector Magnetic Field Sensing Using Single Phase Magneto-Electric Thin Films

We present the design and experimental implementation of a sensing device for determining the magnitude and direction of low-frequency ac magnetic fields using two identical magneto-electric (ME) thin films. The ME films were fabricated from a single-phase SrCo $_{2}$ Ti $_{2}$ Fe $_{8}$ O $_{19}$ M-type source and deposited on a 500-nm-thick indium tin oxide layer on a silicon substrate using pulsed laser deposition. The device size (in volume) is 0.02cm3 for each ME film, and the proposed experimental setup can be used to detect ac magnetic fields that were generated from a solenoid coil located at a distance of 10mm. In this article, we also made improvements to our previous H-field sensing circuit that detects the change in capacitance of the ME film when an external field H $_{\text{ext}}$ is applied. The experimental results demonstrate that the proposed vector sensing approach using two ME films can establish the magnitude and angle of external magnetic fields with maximum detection errors of 13 and 16, respectively.

Harnessing Cell Dynamic Responses on Magnetoelectric Nanocomposite Films to Promote Osteogenic Differentiation.

The binding of cell integrins to proteins adsorbed on the material surface is a highly dynamic process critical for guiding cellular responses. However, temporal dynamic regulation of adsorbed proteins to meet the spatial conformation requirement of integrins for a certain cellular response remains a great challenge. Here, an active CoFe2O4/poly(vinylidene fluoride-trifluoroethylene) nanocomposite film, which was demonstrated to be an obvious surface potential variation (Δ V ≈ 93 mV) in response to the applied magnetic field intensity (0-3000 Oe), was designed to harness the dynamic binding of integrin-adsorbed proteins by in situ controlling of the conformation of adsorbed proteins. Experimental investigation and molecular dynamics simulation confirmed the surface potential-induced conformational change in the adsorbed proteins. Cells cultured on nanocomposite films indicated that cellular responses in different time periods (adhesion, proliferation, and differentiation) required distinct magnetic field intensity, and synthetically programming the preferred magnetic field intensity of each time period could further enhance the osteogenic differentiation through the FAK/ERK signaling pathway. This work therefore provides a distinct concept that dynamically controllable modulation of the material surface property fitting the binding requirement of different cell time periods would be more conducive to achieving the desired osteogenic differentiation.

Magneto-induced polarization enhancement and magneto-dielectric properties in oxygen deficient La0.67Sr0.33MnO3-/BaTiO3 composite film

Magnetoelectric composite film is an important type of multiferroic materials, which is usually composed of typical ferromagnetic and ferroelectric materials. For the ferroelectric layer, BaTiO3 (BTO) attracts much attention due to its lead-free characteristic. For the ferromagnetic layer, doped manganite (R1-xAxMnO3) has been a good candidate for designing the advanced multiferroic films. Multiple interactions among the freedom degrees of charge, orbital, spin and lattice inside the doped manganite bring many additional properties into the manganite based composite films. At present, most of researches of manganite/BTO focus on the stoichiometric oxygen ion in manganite. Considering the fact that the oxygen deficiency can remarkably adjust the properties of manganite itself and relevant heterostructure by the interface effect, abnormal magnetoelectric properties are expected in an oxygen deficient manganite/BTO composite film. In this work, a composite film composed of BTO and oxygen deficient La0.67Sr0.33MnO3- (LSMO) is deposited on LaAlO3 001 substrate by the pulsed laser deposition method, and the effects of magnetic field on the properties of polarization and dielectric in a temperature range of 20-300 K are investigated. The X-ray diffraction pattern reveals good epitaxial growth of this bilayer film. The upper LSMO film exhibits semiconductive characteristic (dR/dT 0) in a temperature range of 20-300 K. Magnetization curves indicate that the LSMO keeps ferromagnetic state without any magnetic phase transition in this temperature range. When applying a magnetic fields of 0.8 T, the resistance in LSMO is observed to decrease. The changing rate MR=|R0.8 T-R0 T|/R0 T decreases from 45.28% at 30 K to 0.15% at 300 K. This composite film exhibits remarkable temperature-dependent magneto-induced ferroelectric and dielectric change. It is found that the remanent polarization (Pr) and coercive electric field (Ec) are enhanced by the 0.8 T magnetic field. The maximum changing rates of Pr and Ec are 111.9% and 89.6% at the temperatures of 40 K and 60 K, respectively. The magnetic field enhances the dielectric constant , but suppresses the dielectric loss tan . The maximum changing rates of and tan both occur at 60 K with the values of 300% and 50.9%. The temperature at which appear the maximum magneto-induced relative changes of polarization and dielectric parameters is accordant with the temperature at which occurs the peak value of magnetoresistance, which indicates a charge-based coupling in this heterojunction. A potential mechanism is that the magnetic field promotes the degree of parallelism of local spin magnetic moment of Mn ion, and produces an indirect effect on BTO layer by the spin-obital coupling and interface effect. Our findings make the oxygen deficient LSMO/BTO heterojunction promising for the design of multiferroic devices.

Visible light induced ferroelectric depolarization in Pb(Zr0.53Ti0.47)O3/La0.67Sr0.33MnO3 magnetoelectric composite film

The visible light induced ferroelectric property for Pb(Zr0.53Ti0.47)O3/La0.67Sr0.33MnO3 (PZT/LSMO) film is investigated, and the temperature dependent ferroelectric responses is discovered. When temperature is lower than the metal–insulator transition temperature (TMI) of LSMO, both of the remanent polarization and coercive field of PZT are significantly depressed by the laser irradiation, whereas they keep unchanged once temperature rises higher than TMI. The temperature-dependent variation of ferroelectricity may be caused by photoinduced demagnetization in LSMO layer and photovoltage produced in the PZT/LSMO heterojunction. The optical modulation on ferroelectricity makes this heterojunction potential application in new ferroelectric devices.

Room Temperature Sensing of Magnetic Fields Using Magnetoelectric Thin Films

We present the design, characterization, and fabrication of a sensing device for measuring low-frequency ac magnetic field variations using a single-phase magnetoelectric (ME) thin film. This ME device is fabricated using SrCo 2 Ti 2 Fe 8 O 19 and deposited on a 500-nm-thick Indium Tin Oxide layer. The ME film is then deposited on a silicon substrate using a pulsed laser deposition technique. The device size (volume) is 0.02 cm 3 , and its overall power consumption is 14 μW. We also show that this sensing device can be used to detect low ac and dc magnetic fields. In this experiment, we employ a modified Wheatstone bridge circuit as an alternative approach to detect the change in capacitance of the ME film when an external field H ext is applied. The circuit uses a combination of an ac input source and a variable capacitor to balance the bridge when the external field is zero. The experimental results demonstrate that the ME device can detect both ac and dc magnetic fields (up to 0.3 T) and is particularly sensitive for ac field sensing. Since the ME device employs a single-phase material, it is not only relatively simple to fabricate but also capable of operating at very low voltages and, therefore, suited for planar integration and compatibility with other integrated circuits.

Principle of tunable chemical vapor detection exploiting the angular Goos–Hänchen shift in a magneto-electric liquid-crystal-based system

We present a theoretical investigation of the angular Goos–Hänchen shift (GHS) of a Gaussian light beam upon reflection from a multilayered structure consisting of a nematic liquid crystal (LC) cell sandwiched between electrodes and deposited on a magneto-electric/non-magnetic bilayer. We show that the angular GHS can be enhanced and controlled both via a voltage applied to the LC cell and a magnetization reversal in the magneto-electric film. We describe the principle of an optical sensor of chemical vapors in the vicinity of the structure based on the voltage-induced tunability of the angular GHS.

Magnetoelectric Neural Modulation

A method to remotely stimulate neurons would allow for the study of deep brain regions in freely moving animals and lead to potential applications in new forms of treatment for disorders such as Parkinson's disease. For clinical applications, techniques that do not require genetic manipulations are most desirable. An ideal neuromodulation device would be enclosed in the tissue after implantation and externally activated to deliver a specific electrical signal to a deep brain region without the use of wires, which can cause tissue damage. Using the magnetoelectric coupling between a magnetostrictive and piezoelectric material we propose the use of magnetoelectric thin films as a novel neuromodulation device. This device will allow for specific less-invasive neural modulation by the application of a small external magnetic field that is transformed to a local electric field.To create a biocompatible magnetoelectric film we bonded a piezoelectric material polyvinlydene fluoride and a magnetostrictive material Metglas. We then encapsulated the films to make them biocompatible. These films can generate voltages above four volts under resonant conditions using alternating magnetic fields with an amplitude of about 0.5 mT. We can also design the film geometry to resonate at different frequencies, which allows us to independently control multiple stimulation channels on a device. We have also shown these films to be biocompatible in vitro using cell viability assays over a period of seven days with no loss of device functionality. In conclusion, these biocompatible magnetoelectric devices can convert magnetic fields that can penetrate the brain into electric fields that interact with surrounding cells to modulate their activity. Magnetoelectric materials could also be developed into a novel deep brain stimulation treatment for neural disorders like Parkinson's disease using devices that cause less neural damage compared to current electrodes.

Frequency Response of a Coupled Magnetoelectric Hexaferrite Film on a Spiral Coil

This letter presents an experimental assessment and evaluation of the frequency response of a recently proposed magneto-electric (ME) device (suitable for H- and E -field sensor and tuning applications). The device is fabricated by incorporating a single-phase ME hexaferrite thin film on a silicon substrate, which is able to operate at a few volts. A conductive buffer layer of indium tin oxide is introduced between the Si substrate and the ME film to accommodate the voltage reduction for ME film excitation at room temperature. A planar spiral coil is then utilized for application or detection of an ac magnetic field by excitation of the ME film or change in magnetization as a flux, respectively. Through a nonlinear experiment, the frequency of the signals for both spiral coil and ME film is changed in the range of 1-10 MHz. The voltage across the coil is then measured as a function of the two sources with coupled frequencies. Coupling is, therefore, related to the frequency and amplitude of both these signals. The frequency response in these experiments provides a better understanding of the ME effect coupling. Experimental data confirm these findings.

Magneto-Electric Effect Modeled in a Nonlinear Experiment

This letter presents a nonlinear model and experimental assessment of a magneto-electric (ME) device fabricated using a hexaferrite film and a spiral coil. In both the model and experiment, two sources are applied to the ME film and the spiral coil. The ME effect is modeled by two equation-based sources for generating the ME effect from the ME film to the spiral coil (and vice versa). A simple equivalent circuit model is used. In the nonlinear experiment, the two different sources are applied in a frequency range of 1-40 MHz. The voltage across the coil is measured as a function of the two sources with coupled frequencies and amplitude. In the simulation, the voltage on the spiral coil is a combination of the two sources modulated in the frequency domain; moreover, they are in agreement with experimental results showing that the output voltage of the spiral coil is a function of not only its direct source, but also the source on the ME film (so arising from the ME coupling). Between the experiment and simulation, the average amplitude difference is approximately 20%, whereas the resonance peaks are in agreement.

Field Sensors and Tunable Devices Using Magnetoelectric Hexaferrite on Silicon Substrates

In this paper, the H-field and E-field sensors as well as the tunable devices are fabricated by utilizing single-phase magnetoelectric (ME) hexaferrite thin films on a silicon substrate. A buffer layer of indium–tin oxide is introduced between the Si wafer and the ME film. The required voltage excitations are reduced to values below 1 V at room temperature, hence making these devices compatible with planar integrated circuits (ICs) and CMOS. A planar spiral coil is utilized in a frequency range of 100 Hz to 10 MHz for sensing applications by applying an ac field (electric or magnetic) for excitation of the ME film. For H-field (E-field) sensing, a sensitivity of up to 1000 Vm $^{-1}$ /G ( $10^{-7}$ G/Vm $^{-1})$ is attained. The corresponding sensitivity for H-field is $4 \times 10^{4}$ up to $10^{7}$ V/T for 3 kHz up to 10 MHz. Tunability of up to 60% is achieved for tunable inductor applications; moreover, a change of 26% in voltage is observed at a single frequency by applying a voltage of 3 V on the ME film, thus performing as a single frequency detector. The proposed devices are made of single-phase materials, so they are simple to fabricate and capable to operate at the voltages of few volts; these features make them viable as a new generation of the ME devices for integration in ICs.

Influence of the linear magneto-electric effect on the lateral shift of light reflected from a magneto-electric film

We present a theoretical investigation of the lateral shift of an infrared light beam reflected from a magnetic film deposited on a non-magnetic dielectric substrate, taking into account the linear magneto-electric interaction in the magnetic film. We use the stationary phase method to evaluate the lateral shift. It is shown that the magneto-electric coupling leads to a six-fold enhancement of the lateral shift amplitude of a p-(s-) polarized incident beam reflected into a s-(p-) polarized beam. A reversal of the magnetization in the film leads to a nonreciprocal sign change of the lateral shift.