The origin of thermally stimulated depolarization currents in multiferroic CuCrO2

Abstract

We have measured the thermally stimulated depolarization currents (TSDC) of multiferroic CuCrO2. We observe a sharp peak near the antiferromagnetic ordering temperature TN ∼ 24 K, below which the material becomes ferroelectric. In addition, we observe three other peaks above TN at ∼50, 120, and 150 K, when the poling is done at a higher temperature than TN. These peaks are not related to exotic kinds of ferroelectricity. Using the poling field dependence of TSDC, the origins of the first two peaks are ascribed to the relaxation of defect dipoles and to space charge relaxation due to the release of trapped charges, respectively. Upon polishing, the peaks observed at 120 and 150 K disappear, suggesting a surface defect origin. Moreover, using temperature and frequency dependent dielectric measurements, we find Maxwell-Wagner type dielectric relaxation. In connection with the mechanism of one of the TSDC peaks, we suggest a Schottky barrier formation to explain the dielectric relaxation.