Temperature- and Frequency-Dependent Dielectric Properties of La_1.5Sr_0.5NiO_4-δ

We report the temperature-dependent resistivity and dielectric function (1 kHz~3 MHz) of a charge ordering system La_1.5Sr_0.5NiO_4-δ The primary data of ac impedance was measured by a four-terminal pair arrangement. Above 180 K, the resistivity is independent of frequency. At lower temperatures, the dielectric function could not be fitted by a Debye model with a single relaxation time, it should have a distribution. At T=130 K, there is a sudden increase in the ρ-T relation, meanwhile an anomaly dielectric response occurs on the temperature dependant dielectric spectrum in the whole measured frequency range, in which the dielectric constant has a high value even at high frequency region. Our analysis suggests that the current system would be more consistent with the Zener polaron model.