Thermally stimulated depolarization current properties of Co₄Nb₂O₉ ceramics

Abstract

Thermally stimulated depolarization current in magnetoelectric antiferromagnet Co4Nb2O9 were investigated above Néel temperature, and five current peaks (denoted as P0 ~ P4 in the order of ascending temperature) were observed. These peaks are related to holes which can be trapped by cobalt vacancies, their surrounding medium (self‐trapped), internal, and surface barrier layers. In low‐temperature range, the holes are bound to cobalt vacancies. The polarization caused by bound holes yields P0 peak at 46 K. In middle‐temperature range, the holes are localized by the surrounding medium forming polarons. The hopping motions of the self‐trapped holes create P2 peak at ~120 K. The microdisplacements around their locating positions for the self‐trapped holes lead to P1 peak, whose peak temperature strongly depends on the poling temperature but lower than that of P2 peak. In high‐temperature range, the holes are trapped by internal and surface barrier layers giving rise to P3 peak at ~150 K and P4 peak at ~230 K, respectively.