A ferroelectric crystal exhibits a stable and switchable electrical polarization that is manifested in the form of cooperative atomic displacements. A ferromagnetic crystal exhibits a stable and switchable magnetization that arises through the quantum mechanical phenomenon of exchange. There are very few 'multiferroic' materials that exhibit both of these properties, but the 'magnetoelectric' coupling of magnetic and electrical properties is a more general and widespread phenomenon. Although work in this area can be traced back to pioneering research in the 1950s and 1960s, there has been a recent resurgence of interest driven by long-term technological aspirations.

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Multiferroic and magnetoelectric materials

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.

https://iopscience.iop.org/article/10.1088/0022-3727/38/8/R01/pdf

Revival of the Magnetoelectric Effect

Multiferroic materials, which show simultaneous ferroelectric and magnetic ordering, exhibit unusual physical properties — and in turn promise new device applications — as a result of the coupling between their dual order parameters. We review recent progress in the growth, characterization and understanding of thin-film multiferroics. The availability of high-quality thin-film multiferroics makes it easier to tailor their properties through epitaxial strain, atomic-level engineering of chemistry and interfacial coupling, and is a prerequisite for their incorporation into practical devices. We discuss novel device paradigms based on magnetoelectric coupling, and outline the key scientific challenges in the field.

Multiferroics: progress and prospects in thin films.

Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. A...

Multiferroic magnetoelectric composites: Historical perspective, status, and future directions

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Piezoelectric devices based on a variety of vibration modes are widely utilized in high-tech fields to make a conversion between mechanical and electrical energies. The excitation of single or coupled vibration modes of piezoelectric devices is mainly related to the structure and property of piezoelectric materials. However, for the generally used piezoelectric materials, e.g., lead zirconate titanate ceramics, most of piezoelectric coefficients in the piezoelectric matrix are equal to zero, resulting in many piezoelectric vibration modes cannot be excited, which hinders the design of piezoelectric devices. In this work, an orderly stacked structure with piezoelectric strain units is proposed to achieve all nonzero piezoelectric coefficients, and consequently generate artificially coupled multi-vibration modes with ultrahigh strains. As an example, an orderly stacked structure with two piezoelectric strain units stator, corresponding to 31-36 coupled vibration mode, was designed and fabricated. Based on this orderly stacked structure with two piezoelectric strain units stator, we made a miniature ultrasonic motor (5 mmLength × 1.3 mmHeight × 1.06 mmWidth). Due to the ultrahigh strain of the 31-36 coupled vibration mode, the velocity per volume of the motor reached 4.66 s-1 mm-2. Furthermore, its moving resolution is around 3 nm, which is two orders higher than that of other piezoelectric motors. This work sheds a light on optimizing the performance of state-of-the-art electromechanical devices and may inspire new devices based on multi-vibration modes. 

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Miniaturized electromechanical devices with multi-vibration modes achieved by orderly stacked structure with piezoelectric strain units

The invention provides a lead tin niobate-bismuth scandate-lead titanate ternary system high temperature piezoceramic material and a preparation method thereof. The structure of the material is as shown in the following general formula: 0.05Pb(Sn1/3Nb2/3)O3-(0.95-x)BiScO3-xPbTiO3, wherein x and 0.95-x respectively represent the mole percentages of PbTiO3 and BiScO3; x ranges from 0.60-0.63. The invention further provides a preparation method of the high temperature piezoceramic material. According to the lead tin niobate-bismuth scandate-lead titanate ternary system high temperature piezoceramic material provided by the invention, by changing the material system, the use amount of Sc is reduced compared with that of an existing piezoceramic material BiScO3-PbTiO3, the cost of industrial production is lowered, and under the condition that a relatively high Curie temperature is kept, the piezoelectric property of the material is further improved.

Lead tin niobate-bismuth scandate-lead titanate ternary system high temperature piezoceramic material and preparation method thereof

Piezoelectric actuator and manufacturing method thereof

Multiferroic magnetoelectric (ME) composites have been continually attracting researchers' attention because of the significant potential for building functional devices. Unlike conventional ME devices under quasi-static or low-power excitation, e.g., sensors, energy harvesters, and random memories, high-power ME devices like recently proposed ME antennas will perform complex dynamic behavior. The voltage-driven nonlinearity in 1–1-typed ME resonators was reported from the perspective of frequency-response curve in our last work. Here, we described both theoretically and experimentally a previously unobserved jumping and hysteresis effect in its magnetic bias characteristic. A direct link between the bias-response and the frequency-response characteristics was also experimentally provided to analyze the origin of the nonlinear behavior in the bias-response curve. In addition, the cubic spring constant k3 was theoretically calculated and compared to qualitatively explain the difference of our obtained threshold voltage that generated the first and second jumping resonances in the dual-peak bias-response curve. In contrast to our previous research, this work reveals the loading direction of the applied magnetic bias field, which plays a significant role when we consider the selection of an optimized bias field for high-power ME devices. Moreover, the sharp jumping in the bias-response curve is also a potential for opening dimensions for ME community.

Jumping and hysteresis effect in 1–1-typed magnetoelectric resonators

Comprehensive high-precision actuations are in growing demand to meet diversified needs in scientific and industrial fields. However, it is a great challenge for piezoelectric actuators with compact structure to guarantee high load capacity and wide velocity range (including fast motion velocity and high resolution) simultaneously. Herein, inspired by bionic methodology, a high-power-density bar-type linear piezoelectric ultrasonic actuator (LPUA) operating in the single second bending (B2) mode with elaborate working principle is developed by imitating bicycle movement mechanism. The proposed B2-LPUA actuator is simple and easy for miniaturization without multimodal decoupling problem. Under only one-phase voltage drive, the miniature bar-type actuator can produce continuously bidirectional motions with the maximum driving velocity, minimum driving velocity, load, and output power of 211.2 mm/s, 3.3 μm/s, 5.4 N, and 218.3 mW, respectively, and the tested minimum step displacement is only 33 nm in open-loop control. Especially, its output power density (243 mW/cm3 or 4.112 mW/cm3⋅kHz) is at least twice larger than most reported LPUAs. The experimental results indicate that the proposed piezoelectric actuator with excellent actuation performances has broad application scenarios, and its bionic motion design method would have inspirational significance for creating new piezoelectric devices with more attractive properties.

Shuxiang Dong

Papers

Miniaturized electromechanical devices with multi-vibration modes achieved by orderly stacked structure with piezoelectric strain units

Lead tin niobate-bismuth scandate-lead titanate ternary system high temperature piezoceramic material and preparation method thereof

Piezoelectric actuator and manufacturing method thereof

Jumping and hysteresis effect in 1–1-typed magnetoelectric resonators

A High-Power-Density Piezoelectric Actuator Operating in Bicycling Movement Mechanism