Multiferroic Magnetoelectric Composites/Hybrids

Abstract

The multiferroic magnetoelectric (ME) effect describes the coupling between the electric and magnetic fields, and is defined as a generated electric polarization P in response to an externally applied magnetic field H (direct ME effect), or an induced magnetization M with an applied electric field E (converse ME effect). Unfortunately, the ME coupling of all the known single-phase materials is usually small at room temperature to be practically applicable. Alternatively, multiferroic composites (ferroelectric and ferri/ferromagnetic phases) typically yield a giant ME coupling response above room temperature, which makes them attractive for technological applications. In the composites, the ME effect is generated as a product property of the magnetostrictive effect (magnetic/mechanical effect) and piezoelectric effect (mechanical/electric effect). To achieve a large ME response, piezoelectric constituent with a high piezoelectric coefficient, magnetostrictive constituent with a high piezomagnetic coefficient, and good coupling between the piezoelectric and magnetostrictive constituent are required. In this chapter, we begin with a brief overview of the development of each material’s constituent (piezoelectrics and magnetostriction) providing a list of state-of-the-art piezoelectric and magnetostrictive materials in multiferroic ME hybrid. Next, a discussion is provided on the composite structure and interface elastic coupling between the piezoelectric and magnetostrictive phases. After that we describe the fabrication process of several important ME hybrids with different phase connectivity, interface, and configuration. Considering the importance of nanostructure and 2–2-type ME composite, the scaling effect and theoretical modeling for these architectures are presented in some detail. Following these sections, some of the potential applications for ME hybrids are reviewed and illustrated by examples. Lastly, the chapter is concluded with a brief summary and future perspective.