Progress, challenges, and perspectives of magnetoelectric composites and devices based on relaxor-PT single crystals

Magnetoelectric (ME) composites exhibit robust ME interfacial coupling because of the strong interaction between piezoelectricity and magnetostriction. The presence of two novel functionalities, i.e., direct and converse ME couplings, makes them ideal candidates for multifunctional devices such as energy harvesters, magnetic field sensors, ME random access memories, and ME antennas. In these ME composites, ME coupling is strongly dependent on the superior physical properties of the piezoelectric and magnetostrictive materials. Therefore, magnetostrictive materials with excellent piezomagnetic coefficients and piezoelectric materials with excellent piezoelectric coefficients are required to achieve a large ME coupling. Among the various piezoelectric materials, ferroelectric relaxor-PbTiO3 (PT) single crystals have been used extensively as piezoelectric constituents because of their ultrahigh piezoelectric and electromechanical properties. Furthermore, the domain structure and crystal orientation of the relaxor-PT single crystals exhibit extraordinarily large piezoelectric and electromechanical properties. Owing to these multifunctional properties, relaxor-PT single-crystal-based ME composites have been widely used for studying direct and converse ME couplings in ME composites in recent years. Relaxor-PT single-crystal-based ME composites show excellent ME coupling, e.g., the highest ME voltage coefficient, equivalent magnetic noise, and output power of 7000 V cm−1 Oe−1@ 23.23 kHz, 6 pT/√Hz @1 Hz, and 19 mW @ 60 Hz, respectively, which are one of the best-reported values in ME composites so far. Considering the vast research on relaxor-PT single-crystal-based ME composites, we present a detailed review of the recent progress, challenges, and perspectives of ME composites and ME devices based on relaxor-PT single crystals.