Magnetoelectric effect in simple collinear antiferromagnetic spinels

Abstract

We report the discovery of the linear magnetoelectric effect in a family of spinel oxides, Co3O4 and MnB2O4 (B = Al, Ga) with simple collinear antiferromagnetic spin structure. An external magnetic field induces a dielectric anomaly at T-N, accompanied by the generation of electric polarization that varies linearly with magnetic field. Magnetization and magnetoelectric measurements on a single crystal of MnGa2O4 together with a phenomenological theory suggest that the easy axis direction is [111] with the corresponding magnetic symmetry R (3) over bar 'm'. The proposed theoretical model of single-ion contribution of magnetic ions located in a noncentrosymmetric crystal environment stands for a generic mechanism for observing magnetoelectric effects in these and other similar materials.