21 - Ferroelectric perovskite–spinel ferrite ceramics

Abstract

Multiferroics are a class of multifunctional materials characterized by the coexistence of at least two ferroic orders (ferroelectric, antiferromagnetic, or ferroelastic) in the same phase. Research in the field of multiferroics dates back to the 1950s, but in the last 10years, key discoveries in theory, synthesis, and characterization techniques have led to a renewed interest concerning the study and applications of such materials. The high interest in multiferroic magnetoelectrics (MEs) can be explained from two points of view: (1) the coexistence of ferroelectricity and ferromagnetism in the same structure, which is highly desired but rarely found in single-phase materials; and (2) the coupling between the magnetic and ferroelectric orders, which might induce novel functionalities, such as a ME effect not present in either state alone. The ME effect represents the appearance of an electric polarization upon applying a magnetic field and/or the appearance of a magnetization under the electric field. Secondary ME coupling may refer in general to a change of a magnetic property (e.g., magnetization, M(H) loop, magnetic permeability, etc.) upon the application of an electric field or vice versa.