Dielectric relaxation and magneto-dielectric effect in polycrystalline Bi0.9Ca0.1FeO2.95

We have investigated temperature, frequency, and magnetic field dependent dielectric properties of polycrystalline Bi0.9Ca0.1FeO2.95. Two dielectric anomalies, near 65 K and 260 K, were observed with the anomaly near 65 K exhibiting distinct frequency dependence as the peak temperature shifts with increasing frequency. The low-temperature dielectric relaxation data that can be fitted to a Vogel-Fulcher expression yielding a characteristic relaxation time of ∼10^-8 s are four orders larger than that of pure BiFeO3 which may be the resultant of the chemical pressure induced by Ca doping. We also observed a switchable magneto-dielectric response in Bi0.9Ca0.1FeO2.95 at room temperature.