Dielectric responses of the layered cobalt oxysulfide Sr_2Cu_2CoO_2S_2 with CoO_2 square-planes

TL;DR

This study investigates the dielectric properties of layered cobalt oxysulfide Sr_2Cu_2CoO_2S_2, revealing temperature-dependent dielectric relaxation linked to magnetic phase transitions and carrier redistribution.

Contribution

It provides new insights into the dielectric responses and magnetic coupling in Sr_2Cu_2CoO_2S_2, highlighting the correlation between dielectric behavior and magnetic states.

Findings

Dielectric constant varies significantly with temperature.

Dielectric relaxation changes systematically with magnetic phase.

Carrier distribution is affected by magnetic ordering.

Abstract

We have studied the dielectric responses of the layered cobalt oxysulfide Sr$_2$Cu$_2$CoO$_2$S$_2$ with the CoO$_2$ square-planes. With decreasing temperature below the N\'eel temperature, the resistivity increases like a semiconductor, and the thermopower decreases like a metal. The dielectric constant is highly dependent on temperature, and the dielectric relaxation is systematically changed with temperature, which is strongly correlated to the magnetic states. These behaviors suggest that carriers distributed homogeneously in the paramagnetic state at high temperatures are expelled from the antiferromagnetically ordered spin domain below the N\'eel temperature.