Phase coexistence and multiple dielectric relaxations in the single layered manganite Nd0.22Sr1.78MnO4

Abstract

We report the magnetization, dc and ac conductivities, and dielectric response of the single layered manganite with formulation Nd0.22Sr1.78MnO4. The sample undergoes charge/orbital ordering approximately below 260 K, and a region of thermal hysteresis is observed in the magnetization data between 175 and 50 K. The dc electrical resistivity indicates Arrhenius type thermally activated behavior at high temperature and a complicated conduction behavior at low temperature. In the ac conductivity measurement, the universal dielectric response is observed over the selected frequency range at low temperature (below 155 K). The sample shows dielectric response very similar to polycrystalline CaCu3Ti4O12 and other manganites, with a value of the room temperature dielectric permittivity as large as 5500 measured at 5 kHz of frequency. The disorder induced charge localization and the polaron hopping mechanism are possibly responsible for the overall electronic conduction and dielectric response of the sample. The sample shows signature of multiple relaxations, which is intrinsic to the sample and presumably related to the phase separation around the first order structural transition in the charge/orbital ordered phase.