Phenomenological theory of the magnetoelectric effect in some boracites

Abstract

An explanation is given for the narrow peak in the temperature dependence of the component α 32 of the magnetoelectric effect tensor near the transition at T=T c to the m′m2′ phase observed in the boracites. A phenomenological approach is used which is based on the symmetry of the cubic phase of the crystals. The change in the sign of α 23 and α 32 observed in some of the boracites as the temperature is lowered is attributed to the low value of T c.