Magnetothermopower in Nd1-xEuxNiO3 compounds (original) (raw)

2007, Journal of Applied Physics

We have measured magnetization M(T ,H), thermal conductivity κ(T ,H), and thermopower S(T ,H) of polycrystalline samples of Nd1-xEuxNiO3, 0⩽x⩽0.35, as a function of temperature and external magnetic field. The data indicate a metal-insulator (MI) transition in a wide range of temperature (200<TMI<325K). The magnetic susceptibility χ(T ) data, after the subtraction of the rare-earth contribution, exhibit a Curie-Weiss-like behavior at temperatures above TMI. Although a clear antiferromagnetic AF transition of the Ni sublattice is observed at TN⩽TMI, χ(T ) still increases down to 5K, suggesting a heterogeneous ground state. The thermal conductivity of the NdNiO3 compound is not affected by an external magnetic field of 90kOe in a wide range of temperature, and its temperature dependence below 15K is approximately quadratic, strongly suggesting the presence of disorder. S(T ) is negative above TMI and varies linearly with temperature. Below TMI, there is a minimum close to 120K, and S(T ) changes its sign at T ˜30K, indicating a competition between two types of charge carriers. A pronounced peak in S(T ) at TS˜20K is observed and the peak remains unaltered under magnetic fields up to 90kOe. However, its magnitude is enhanced by ˜25% with applied magnetic field, exhibiting a clear magnetothermopower effect. The combined results indicate a coexistence of ordered and disordered phases below TN and that an applied magnetic field is suitable for enhancing the thermoelectric properties close to TS.