Magnetoelectric memory effect of paramagnetic nonpolar phase in Co4Nb2O9

Abstract

A polarization memory effect of the paramagnetic nonpolar phase is observed in magnetoelectric antiferromagnet Co4Nb2O9, which has a magnetic field induced polarization in the antiferromagnetic phase. Following magnetoelectric poling in the polar phase, the nonpolar paramagnetic state retains a strong memory of polarization. When reentering the polar phase without applying the electric field, a polarization along the initial poling direction is recovered. If the applied magnetic field while staying in the paramagnetic phase is weakened, the memory effect is enhanced. With reversing this magnetic field, the polarization is also reversed when reentering the polar phase. The memory effect can be attributed to the ferroelectric seeds forming in the nonpolar phase due to short-range magnetic ordering as evidenced by magnetic entropy data.