Inverse Magnetoelectric Effect Research Articles

Characterization of In‐Plane Piezoelectric Strain of Ferroelectric Thin Films by the Magnetoelectric Coupling Effect

Piezoelectric response of the ferroelectric/piezoelectric thin films is crucial for actuation of micro‐electromechanical systems (MEMS) devices as well as strain‐mediated electronic devices. Among many piezoelectric modes, longitudinal and transverse piezostrain is the most widely used. Various methods have been well established for quantitative characterization of the longitudinal piezostrain, such as laser interferometer and piezoelectric force microscopy. However, it is still a great challenge to characterize transverse piezostrain. Herein, a new method is established to characterize the transverse (in‐plane) piezostrain of ferroelectric/piezoelectric thin films by the inverse magnetoelectric (ME) coupling effect. A ferromagnetic thin film is patterned onto the ferroelectric thin film to form an artificial multiferroic heterostructure. The transverse piezostrain can transfer from the ferroelectric layer to the ferromagnetic layer and shift its ferromagnetic resonance field through the ME coupling effect. By comparing with a control sample of “bulk piezoceramic/ferromagnetic thin film” whose in‐plane piezostrain can be easily measured, the in‐plane piezostrain and piezoelectric coefficient of the ferroelectric thin films are then estimated. The in‐plane piezoelectric coefficient d31 and piezoelectric strain S31 of Pb(Zr,Ti)O3 (PZT) thin films are measured by this method. This new method will promote to fully understand the piezoelectric properties of the ferroelectric/piezoelectric thin films.

Ferroelectric hysteresis and magnetoelectric effect in orthorhombic Dy-=SUB=-1-x-=/SUB=-Ho-=SUB=-x-=/SUB=-MnO-=SUB=-3-=/SUB=- single crystals

In Dy1-xHoxMnO3 single crystals with the orthorhombic space group Pbnm, ferroelectric hysteresis loops were measured for compositions with x=0 and 0.3. As the content of Ho3+ ions increases, the hysteresis loop narrows and for x=0.3 it no longer manifests itself. An analysis of the signal corresponding to the hysteretic behavior of a ferroelectric showed that even harmonics can be obtained only if the hysteresis loop is not symmetric about the abscissa axis. In view of the latter, the hypothesis that the second harmonic of the magnetoelectric effect is a consequence of the complex dependence of the polarization on time due to its hysteresis becomes doubtful. Measurements of the dependence of the inverse magnetoelectric effect on the amplitude of the applied electric field Delta M(E) showed that the first harmonic remains linear with respect to the electric field even in the electric field strength region where the domain structure of the ferroelectric is rearranged. Keywords: multiferroics, ferroelectricity, hysteresis.

Сегнетоэлектрический гистерезис и магнитоэлектрический эффект в орторомбических монокристаллах Dy-=SUB=-1-x-=/SUB=-Ho-=SUB=-x-=/SUB=-MnO-=SUB=-3-=/SUB=-

In Dy1-xHoxMnO3 single crystals with the orthorhombic space group Pbnm, ferroelectric hysteresis loops were measured for compositions with x=0 and 0.3. As the content of Ho3+ ions increases, the hysteresis loop narrows and for x=0.3 it no longer manifests itself. An analysis of the signal corresponding to the hysteretic behavior of a ferroelectric showed that even harmonics can be obtained only if the hysteresis loop is not symmetric about the abscissa axis. In view of the latter, the hypothesis that the second harmonic of the magnetoelectric effect is a consequence of the complex dependence of the polarization on time due to its hysteresis becomes doubtful. Measurements of the dependence of the inverse magnetoelectric effect on the amplitude of the applied electric field ΔM(E) showed that the first harmonic remains linear with respect to the electric field even in the electric field strength region where the domain structure of the ferroelectric is rearranged.

Direct and inverse magnetoelectric effect in orthorhombic single crystals of Dy-=SUB=-1-x-=/SUB=-Ho-=SUB=-x-=/SUB=-MnO-=SUB=-3-=/SUB=-

In this work, the magnetoelectric response in a series of Dy1-xHoxMnO3 crystals with substitution x from 0 to 0.4 was investigated. The measurement results showed that, as x increases, a decrease in both the polarization Pa and the magnitude of the susceptibility of the inverse magnetoelectric effect αba is observed. In addition, the field Hb increases, at which the P_c-> Pa transition is observed, and the temperature range of the existence of the magnetoelectric response decreases. Thus, an increase in the substitution x suppresses the magnetoelectric effect in this series of compounds. The measurement results also indirectly indicate the prolongation of the Pa state and, consequently, of the magnetic state with a cycloid lying in the ab-plane by an external electric field Ea. The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project No.20-42-243008. Keywords: multiferroics, magnetoelectric effect, phase transition, ferroelectricity.

Effect of nonmagnetic substituent Zn on the phase competition and multiferroic properties in the polar magnet Fe2Mo3O8

The polar magnet, Fe2Mo3O8 (FMO), with linear magnetoelectric (ME) coupling, is a promising candidate for multiferroic applications in advanced spin devices. However, a giant magnetic bias (Hb) is needed for optimizing the inverse ME effect, i.e., electric field (E) modulation of magnetization (M), which is still a core issue. Herein, we utilize the chemical doping route to enhance the sensitivity of controlling the competitive magnetic interactions and/or multiferroic phases by means of introducing nonmagnetic Zn2+ ions into FMO crystals. Compared with FMO, the Zn-doped composition (Fe0.95Zn0.05)2Mo3O8 (FZMO) generates three metastable magnetic states in the middle of antiferromagnetic and ferrimagnetic states, along with obvious ferroelectric polarization. The inverse ME effect of FZMO is intact with a relative change of ΔM ≈ 0.06 μB/f.u. responding to an E value of ± 20 kV/cm at 52 K. Most interestingly, the exciting Hb is dramatically dropped to 0.8 T for FZMO from 5.1 T for FMO, which is in favor of the application of ME coupling. It is suggested that the perturbation of magnetic interactions via substituting specific sites by nonmagnetic ions plays a key role in decreasing the exciting Hb without deteriorating the inverse ME coupling in this polar M2Mo3O8 family.

Прямой и обратный магнитоэлектрический эффект в орторомбических монокристаллах Dy-=SUB=-1-x-=/SUB=-Ho-=SUB=-x-=/SUB=-MnO-=SUB=-3-=/SUB=-

In this work, the magnetoelectric response in a series of Dy1-xHoxMnO3 crystals with substitution x from 0 to 0.4 was investigated. The measurement results showed that, as x increases, a decrease in both the polarization Pa and the magnitude of the susceptibility of the inverse magnetoelectric effect αba is observed. In addition, the field Hb increases, at which the Pc→Pa transition is observed, and the temperature range of the existence of the magnetoelectric response decreases. Thus, an increase in the substitution x suppresses the magnetoelectric effect in this series of compounds. The measurement results also indirectly indicate the prolongation of the Pa state and, consequently, of the magnetic state with a cycloid lying in the ab-plane by an external electric field Ea. The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project No.20-42-243008.

Inverse and direct magnetoelectric effects in orthorhombic DyMnO3 manganite single crystals

Correlations between the direct and inverse magnetoelectric effects in orthorhombic DyMnO3 single crystals have been investigated. In the inverse magnetoelectric effect, the magnetic moment of the crystal appears to have a contribution that is sinusoidal oscillating in ac electric fields below the temperature TFE of ferroelectric phase transition. The first and the second harmonics of the inverse magnetoelectric effect are clearly detected. The magnetoelectric susceptibilities α and β, corresponding to first and second harmonics, are found to correlate with the derivative of polarization with respect to the magnetic field. The influence of the magnetic and electric regimes during cooling on magnetoelectric effects has also been studied. The maximum change in the magnetic moment of a sample under the action of electric fields is observed under the same (T, H) conditions as the rotation of the spontaneous polarization vector from the crystallographic c direction to the a axis in the magnetic field H || b.

Observation of the inverse magnetoelectric effect in PZT/FeCuNbSiB two-layered composite structures

In recent years, much attention has been paid to the study of magnetoelectric (ME) effects in solids, which was caused by their potential practical applications. Of particular interest are composite multiferroic materials containing ferroelectric and ferromagnetic phases, since significant ME responses may occur in them. This paper is devoted to the study of the inverse ME effect in a two-layered composite sample consisting of a piezoelectric Pb(Zr, Ti)O3 (PZT) plate and an amorphous FeCuNbSiB ferromagnetic ribbon. It was found that the inverse ME effect depends on the magnitudes of the external magnetic field H, the electric voltage U and on the mutual orientation of H and U.

Magnetoelectric effects in superconductor/ferromagnet bilayers

We demonstrate that the hybrid structures consisting of a superconducting layer with an adjacent spin-textured ferromagnet demonstrate the variety of equilibrium magnetoelectric effects originating from coupling between the conduction electron spin and superconducting current. By deriving and solving the generalized Usadel equation which takes into account the spin-filtering effect we find that a supercurrent generates spin polarization in the superconducting film which is non-coplanar with the local ferromagnetic moment. The inverse magnetoelectric effect in such structures is shown to result in the spontaneous phase difference across the magnetic topological defects such as a domain wall and helical spin texture. The possibilities to obtain dissipationless spin torques and detect domain wall motion through the superconducting phase difference are discussed.

Study of inverse magnetoelectric effect in FeBO3-based composites using optical methods

Study of inverse magnetoelectric effect in FeBO3-based composites using optical methods

Spin-orbit torque in a three-dimensional topological insulator–ferromagnet heterostructure: Crossover between bulk and surface transport

Current-driven spin-orbit torques are investigated in a heterostructure composed of a ferromagnet deposited on top of a three dimensional topological insulator using the linear response formalism. We develop a tight-binding model of the heterostructure adopting a minimal interfacial hybridization scheme that promotes induced magnetic exchange on the topological surface states, as well as induced Rashba-like spin-orbit coupling in the ferromagnet. Therefore, our model accounts for spin Hall effect from bulk states together with inverse spin galvanic and magnetoelectric effects at the interface on equal footing. By varying the transport energy across the band structure, we uncover a crossover from surface-dominated to bulk-dominated transport regimes. We show that the spin density profile and the nature of the spin-orbit torques differ substantially in both regimes. Our results, which compare favorably with experimental observations, demonstrate that the large damping torque reported recently is more likely attributed to interfacial magnetoelectric effect, while spin Hall torque remains small even in the bulk-dominated regime.

Nonzero electric polarization and four magnetoelectric states at zero magnetic field in Cr-doped Y-type hexaferrite

We report here an enhanced magnetoelectric effect in a Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22 with Fe3+ ions partially substituted by magnetic Cr3+ ions (i.e., BSZFCO). The direct magnetoelectric effect is persistent up to 250 K, with the maximal susceptibility of ∼1309 ps/m at 75 K. More importantly, the pronounced non-zero electric polarization at zero magnetic field and four magnetoelectric states induced by different initial poling fields make it quite unique to serve in a magnetoelectric device. The stability of the direct (inverse) magnetoelectric effect is confirmed by the nonvolatile behavior in response to the cyclically sweeping magnetic (electric) fields. Our studies provide an insight into the nontrivial properties of BSZFCO, which are promising for multiferroic applications.

A theory of the inverse magnetoelectric effect in layered magnetostrictive–piezoelectric structures

A theory of the inverse magnetoelectric effect in layered structures has been presented. The theory is based on solving the equations of elastodynamics and electrostatics separately for the magnetostrictive and piezoelectric phases, taking into account the conditions at the interface between the phases. Expressions for the coefficient of inverse magnetoelectric conversion through the parameters characterizing the magnetostrictive and piezoelectric phases have been obtained. Theoretical dependences of the inverse magnetoelectric conversion coefficient on the frequency of the alternating-current electric field for the three-layer PZT–Ni–PZT structure and the two-layer terfenol-D–PZT structure have been calculated. The results of the calculations are in good agreement with the experimental data.

Internal friction and magnetoelectric response in two-layer composites Tb0.12Dy0.2Fe0.68–PbZr0.53Ti0.47O3

The inverse magnetoelectric effect and internal friction in two-layer composites based on ferromagnetic Tb0.12Dy0.2Fe0.68 and piezoelectric PbZr0.53Ti0.47O3 are studied in an ac electrical field in the frequency range of 52–213 kHz at temperatures of 293 to 400 K. A correlation is found between the internal friction and the efficiency of the inverse magnetoelectric transformation at resonant frequencies.

Inverse multimodal magnetoelectric effect in piezomagnetostrictive rings

The theoretical investigation of the frequency dependence of the inverse magnetoelectric effect in piezomagnetostrictive rings in the region of radial resonances has been presented. The analytical expression for the coefficient of the inverse magnetoelectric conversion for ring-like samples with the axial polarization has been derived. It has been shown that the energy is redistributed between the modes depending on the structure geometry, which results in the formation of regions where some modes are absent while the amplitude of other ones increases. The voltage transfer coefficient, which can considerably exceed this parameter in the samples shaped as a continuous disc, has been theoretically predicted.

Current Progress of Research on Magnetically-induced Ferroelectrics

Among several different types of magnetoelectric multiferroics, "magnetically-induced ferroelectrics" in which ferroelectricity is induced by complex spin orders, such as spiral orders, exhibit giant direct magnetoelectric effects, i.e., remarkable changes in electric polarization in response to a magnetic field. Not a few spin-driven ferroelectrics showing the magnetoelectric effects have been found in the past decade.[1] However, their induced ferroelectric polarization is much smaller than that in conventional ferroelectrics and mostly develops only at temperatures much lower than room temperature. Thus, the quest for spin-driven ferroelectrics with room temperature operation and/or robust ferroelectric polarization is still a major challenge in magnetoelectric multiferroics research. In this presentation, I will begin with introducing the background of research on magnetically-induced ferroelectrics, and present the following current progress. Recently, some hexaferrites have been found to show direct magnetoelectric effects at room temperature and relatively low magnetic fields.[2] Furthermore these hexferrites show inverse magnetoelectric effects, that is, induction of magnetization by applying electric fields, at room temperature. The results represented an important step toward practical applications using the magnetoelectric effect in spin-driven ferroelectrics. This presentation introduces magnetism and magnetoelectricity of several types of hexaferrites which show magnetoelectric effect at temperatures above room temperature. In addition, I will also introduce our recent work on magnetoelectric perovskite manganites with large magnetically-induced ferroelectric polarization which is comparable to that in conventional ferroelectrics. This work has been done in collaboration with T. Aoyam, K. Haruki, K. Okumura, A. Miyake, K. Shimizu, and S. Hirose.

Specific features of the inverse magnetoelectric effect in two-layered Tb0.12Dy0.2Fe0.68-PbZr0.53Ti0.47O3 composites

The twolayered Tb 0.12Dy0.2Fe0.68-PbZr0.53Ti 0.47O3 magnetoelectric composites have been pre� pared by the deposition of ferromagnetic layers of different thicknesses from a thoroughly mixed Tb0.12Dy0.2Fe0.68 ferromagnetic powder and an epoxy glue on preliminarily polarized PbZr0.53Ti 0.47O3 piezo� electric layers. The dependences of the inverse magnetoelectric effect on the frequency and strength of an electric field, the strength of a constant magnetic field, the thickness of a ferromagnetic layer, the average size of Tb0.12Dy0.2Fe0.68 grains in the ferromagnetic layer, and the temperature have been determined. Conditions for the maximum magnetoelectric response have been established.

Direct and inverse magnetoelectric effects in HoAl3(BO3)4 single crystal

The direct (MEH-) and inverse (MEE-) magnetoelectric effects in the HoAl3(BO3)4 single crystal are studied. Temperature and magnetic field dependences of permittivity of the crystal are investigated. A relation between the investigated effects was established. It was found that the magnetoelectric effect can exist in crystals without magnetic order or spontaneous polarization. It was shown that the phenomena investigated are due to magnetostriction or magnetoelastic effect. The thermodynamic potential was considered for describing magnetoelectric effect at low magnetic fields. The results obtained are explained within a proposed qualitative microscopic model, based on interplay of configuration of 4f- electron subshell of the rare-earth element and applied magnetic or electric field.

Magneto-Electric Effect in Three-Dimensional Coupled Zigzag Chains

Stimulated by recent studies of quantum phases with broken local inversion symmetry, we study the magnetoelectric effect in locally noncentrosymmetric metals. We consider three-dimensional (3D) coupled zigzag chains and demonstrate that the antiferromagnetic moment is induced by the electric current through a staggered antisymmetric spin-orbit coupling. This current-induced magnetism is much larger than that in globally noncentrosymmetric metals. We provide an intuitive understanding of the current-induced antiferromagnetic moment by showing the inverse magnetoelectric effect, that is, the ferroic p-wave charge nematic order accompanied by the asymmetric band structure in the antiferromagnetic state. We also examine conduction electrons coupled to localized spins via Kondo exchange coupling and demonstrate a significant enhancement of the magnetoelectric effect. A possible experimental observation of the magnetoelectric effect in metals is discussed, with focus on LnM_2Al_10 compounds, such as NdRu_Al_10 and TbRu_2Al_10.

Voltage-controlled ferromagnetism and magnetoresistance in LaCoO3/SrTiO3 heterostructures

A LaCoO3/SrTiO3 heterostructure grown on Si (001) is shown to provide electrically switchable ferromagnetism, a large, electrically tunable magnetoresistance, and a vehicle for achieving and probing electrical control over ferromagnetic behavior at submicron dimensions. Fabrication of devices in a field-effect transistor geometry enables application of a gate bias voltage that modulates strain in the heterostructure via the converse piezoelectric effect in SrTiO3, leading to an artificial inverse magnetoelectric effect arising from the dependence of ferromagnetism in the LaCoO3 layer on strain. Below the Curie temperature of the LaCoO3 layer, this effect leads to modulation of resistance in LaCoO3 as large as 100%, and magnetoresistance as high as 80%, both of which arise from carrier scattering at ferromagnetic-nonmagnetic interfaces in LaCoO3. Finite-element numerical modeling of electric field distributions is used to explain the dependence of carrier transport behavior on gate contact geometry, and a Valet-Fert transport model enables determination of spin polarization in the LaCoO3 layer. Piezoresponse force microscopy is used to confirm the existence of piezoelectric response in SrTiO3 grown on Si (001). It is also shown that this structure offers the possibility of achieving exclusive-NOR logic functionality within a single device.