Magnetic Symmetry and Ferroelectricity Induced by Antiferromagnetic Transitions

Abstract

Ferroelectricity is forbidden in centrosymmetric crystals. An antiferromagnetic transition in such crystals which results in a magnetic cell different from the chemical one may lead to noncentrosymmetric magnetic symmetry. It is therefore expected that ferroelectricity may be induced by such a transition. Neutron‐diffraction experiments in CaMn₂O₄, TbCrO₃, BiMn₂O₅ show that the magnetic transitions in these compounds belong to this category. To illustrate this effect from a symmetry point of view an antiferromagnetic transition in a structure belonging to the space group Pmma is considered.