Core–Shell Magnetoelectric Nanoparticles: Materials, Synthesis, Magnetoelectricity, and Applications

Nanoparticles with small diameters and large surface areas have potential advantages and are actively utilized in various fields related to biomedical and catalytic applications. Multifunctional applications can be achieved by endowing nanoparticles with piezoelectric, quantum dot, magnetothermal, and piezoluminescent properties. In particular, multiferroic magnetoelectric nanoparticles (MENPs) can generate electricity by coupling piezoelectric and magnetostrictive properties when an external magnetic field, which is harmless to the human body, is applied. In this regard, magnetoelectricity (ME) induced by a magnetic field makes MENPs useful for various biomedical and electrocatalytic applications. The ME voltage coefficients, which express the efficiency of energy conversion from magnetic field to electricity, show differences depending on the setup for ME measurements of MENPs. Therefore, numerous attempts have been made to optimize the ME characterization method to reduce measurement errors resulting from charge leakages caused by the specimen preparation, as well as to investigate the ME effect of a single nanoparticle. Our review is focused on the structures, syntheses (hydrothermal and sol–gel methods), activation mechanism, and measurement of magnetoelectricity, as well as applications, of core–shell MENPs.