Hybrid Multiferroic Behavior in the Double Perovskite (Ca_0.5Mn_1.5)MnWO₆

Multiferroic materials with ordered electric dipoles and magnetic spins have attracted a great deal of attention in the realms of applications and fundamental science. Multiferroics are generally classified into type I, where (anti)ferroelectric and magnetic transitions are well separated and have completely different origins, and type II, where magnetic structures break the crystallographic inversion symmetry. Type III multiferroics were recently introduced, which are close to type I, but they do not show nonpolar-to-polar structural transitions as polar structures are fixed by chemical order. In this work, we describe dielectric and magnetic behaviors observed in the double perovskites (Ca 0.5 Mn 1.5 )MnWO 6 and (Ca 0.3 Mn 1.7 )MnWO 6, crystallizing in space group P 2 1 / n . The dielectric constants of these compounds showed peaks at T C values of 22 and 27 K, respectively, and followed the Curie–Weiss law in wide temperature ranges between T C and 300 K, where T C is the (anti)ferroelectric transition temperature. This behavior is typical for type I multiferroics with proper (anti)ferroelectric transitions. At the same time, T C matches Néel temperature T N; this behavior is typical for type II multiferroics. Therefore, materials with such behavior can be called hybrid multiferroics.