Revival of the magnetoelectric effect

Abstract

Recent research activities on the linear magnetoelectric (ME) effect—induction of magnetization by an electric field or of polarization by a magnetic field—are reviewed. Beginning with a brief summary of the history of the ME effect since its prediction in 1894, the paper focuses on the present revival of the effect. Two major sources for ‘large’ ME effects are identified. (i) In composite materials the ME effect is generated as a product property of a magnetostrictive and a piezoelectric compound. A linear ME polarization is induced by a weak ac magnetic field oscillating in the presence of a strong dc bias field. The ME effect is large if the ME coefficient coupling the magnetic and electric fields is large. Experiments on sintered granular composites and on laminated layers of the constituents as well as theories on the interaction between the constituents are described. In the vicinity of electromechanical resonances a ME voltage coefficient of up to 90 V cm−1 Oe−1 is achieved, which exceeds the ME response of single-phase compounds by 3–5 orders of magnitude. Microwave devices, sensors, transducers and heterogeneous read/write devices are among the suggested technical implementations of the composite ME effect. (ii) In multiferroics the internal magnetic and/or electric fields are enhanced by the presence of multiple long-range ordering. The ME effect is strong enough to trigger magnetic or electrical phase transitions. ME effects in multiferroics are thus ‘large’ if the corresponding contribution to the free energy is large. Clamped ME switching of electrical and magnetic domains, ferroelectric reorientation induced by applied magnetic fields and induction of ferromagnetic ordering in applied electric fields were observed. Mechanisms favouring multiferroicity are summarized, and multiferroics in reduced dimensions are discussed. In addition to composites and multiferroics, novel and exotic manifestations of ME behaviour are investigated. This includes (i) optical second harmonic generation as a tool to study magnetic, electrical and ME properties in one setup and with access to domain structures; (ii) ME effects in colossal magnetoresistive manganites, superconductors and phosphates of the LiMPO4 type; (iii) the concept of the toroidal moment as manifestation of a ME dipole moment; (iv) pronounced ME effects in photonic crystals with a possibility of electromagnetic unidirectionality. The review concludes with a summary and an outlook to the future development of magnetoelectrics research.

Ferroelectric Field Effect Control of Magnetism in Multiferroic Heterostructures

“…1(c), the magnetoelectric response of the PZT/LSMO multiferroic heterostructure is strongly non-linear, and the response of the system is best described in terms of an effective magnetoelectric susceptibility ∆M/∆E = ∆M/2E c , where E c is the ferroelectric coercive field; at 100 K, we find ∆M/∆E = 6.2 × 10 −3 Oe cm V −1 . This value is significantly larger, by 2-3 orders of magnitude, than typical magnetoelectric coupling coefficients of single-phase multiferroics and comparable to the value obtained for strain-mediated composites Fiebig (2005); Ma et al (2011);Vaz et al (2010a). Given the interfacial nature of the magnetoelectric effect in this system, one alternate measure of the magnetoelectric effect is given in terms of the surface (interface) magnetoelectric coefficient α s , which is obtained by multiplying ∆M/2E c by the LSMO film thickness, yielding α s = 2.9 × 10 −9 Oe cm 2 V −1 at 100 K. In Vaz et al (2010c), the variation of the magnetoelectric response of PZT/LSMO as a function of the temperature is studied, as shown in Fig.…”

“…By judiciously engineering the interfacial properties at the nanoscale, a strong coupling between magnetic and ferroelectric order parameters can be achieved. This new class of artificially structured composite materials exhibits magnetoelectric couplings that are orders of magnitude larger that those typical of single-phase, intrinsic multiferroics Fiebig (2005); Ma et al (2011);Vaz et al (2010a). An example of the promise afforded by this approach is provided by the particular case of the multiferroic perovskite BiFeO 3 , characterized by magnetic and ferroelectric critical temperatures well above room temperature (T m c = 643 K and T e c = 1100 K, respectively) Catalan & Scott (2009).…”

“…This approach to magnetoelectric coupling illustrates the current trend towards engineering larger magnetoelectric couplings by relying on interfacial effects between different materials, an approach that can be traced back to the 1970s, when the first attempts to grow strain-mediated ferroelectric-ferromagnetic composites were made van Suchtelen (1972). In fact, the most common approach to date for achieving a magnetoelectric coupling in composites relies on strain to mediate the magnetic and electrical properties by inducing crystal deformations on either the magnetic phase through the converse piezoelectric effect, or in the ferroelectric phase through magnetostriction Fiebig (2005); Ma et al (2011);Ramesh & Spaldin (2007); Thiele et al (2007); Vaz et al (2009b;. The effect is indirect, but can be optimized to yield large magnetoelectric responses by a suitable choice of the material components and device geometry Nan et al (2008); Srinivasan (2010); Wang et al (2009).…”

Emergent functions of quantum materials

“…36) and hexagonal YMnO 3 (refs 37,38), which show relatively large spontaneous polarization and high ferroelectric/magnetic transition temperatures, albeit with weak coupling between polarization and magnetism. By contrast, type-II multiferroics inherently host strong ME coupling despite smaller ferroelectric polarization and lower transition temperature 38 . Various types of spin orders can produce ferroelectric P. Three representative mechanisms for spin-order-induced ferroelectricity 39,40 are shown in the upper panel of Fig.…”

Structural properties of PbVO3perovskites under hydrostatic pressure conditions up to 10.6 GPa

“…Multiferroic materials, in which ferromagnetism and ferroelectricity coexist, have stimulated a great deal of experimental and theoretical interest in recent years due to their considerable technological and fundamental importance [1][2][3][4][5]. The PbVO 3 tetragonal perovskite (P4mm) (T-phase) was synthesized recently at high pressures and suggested to be a candidate multiferroic with a two-dimensional C-type antiferromagnetism (C-AFM) ordering and a large ferroelectric polarization [6][7][8].…”