Evolution of magnetic and transport properties in Cu doped pyrochlore iridate Eu2(Ir1-xCux)2O7

TL;DR

This study explores how Cu doping affects the magnetic and transport properties of Eu2(Ir1-xCux)2O7, revealing changes in valence states, transition temperatures, and magnetic behaviors, with implications for understanding correlated electron systems.

Contribution

It provides new insights into the effects of Cu substitution on the electronic and magnetic properties of pyrochlore iridates, including valence state changes and magnetic phenomena.

Findings

Cu doping converts Ir4+ to Ir5+ ions.

Metal-insulator transition occurs around 120 K.

Magnetic properties such as exchange bias and negative magnetoresistance increase with Cu concentration.

Abstract

We have investigated the effect of Cu substitution in Eu2(Ir1-xCux)2O7 with the help of magnetic and transport property measurements. XPS measurement reveals that each Cu2+ converts Ir4+ to double amount of Ir5+ ions. The metal-insulator transition temperature (T_MI) is obtained around 120 K. In the insulating phase, at lower temperature below 50 K, the temperature dependent resistivity follows a power law dependence and the magnitude of the exponent increases with Cu concentrations. The temperature dependent thermopower is observed to follow the electrical resistivity down to 50 K, except for a sudden drop in thermopower at temperature below 50 K. We find negligible Hall voltage in the metallic regime of the samples but a sudden Hall voltage is developed below 50 K. We observe bifurcation in zero field cooled and field cooled (ZFC-FC) magnetization below irreversibility temperature, exchange bias and negative magnetoresistance at 3 K and the magnitude of all these properties increases with Cu concentrations. In the insulating region (below 6 K) there exists a linear specific heat and its coefficient decreases with Cu doping which indicates the reduction of spinon contribution with Cu doping.