Magnetoferroelectricity in Cr2BeO4

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Abstract
Chromium chrysoberyl undergoes a phase transformation from a paramagnetic state to a complex antiferromagnetic state at 28 K. The spiral spin structure of the antiferromagnetic state violates all the crystallographic symmetry elements, making Cr2BeO4 potentially ferroelectric. Chynoweth experiments conducted at low temperatures reveal a weak pyroelectric effect which disappears above 28 K. Cr2BeO4 ceramics can be poled electrically between 24 and 28 K, giving rise to remnant polarizations four to six orders of magnitude smaller than normal ferroelectrics. The pyroelectric coefficient and the remnant polarization reverse in sign with the poling field, but no anomalies in the electric permittivity or electric conductivity occur at the Nèel point.