Dielectric relaxation induced internal electric field and its effect on magnetoelectric state in Co4Nb2O9

Pyrocurrent and dielectric properties of magnetoelectric antiferromagnet Co 4 Nb 2 O 9 have been investigated. The sample shows 2 thermally activated dielectric relaxations in the temperature range far above Néel temperature with the low- and high-temperature ones being a dipolar and Maxwell-Wagner relaxations, respectively. Two types of dipoles: relaxing dipoles and magnetic-field-induced dipoles were found in the sample. An internal electric field is formed due to the ordering of relaxing dipoles. Three current peaks were observed. The 2 higher temperature current peaks correspond to the dielectric relaxations. The lowest temperature current peak contains a positive tip and negative dip. The tip and dip are related to the depolarization of ferroelectricity induced by external and internal fields, respectively.