Metallic state and the metal-insulator transition ofNdNiO3

Abstract

We report detailed measurements of the electrical resistivity, Seebeck coefficient, and differential scanning calorimetry across the metal-insulator (MI) transition (${\mathit{T}}_{\mathrm{MI}}$≊205 K) of ${\mathrm{NdNiO}}_3$. As in the isostructural oxide ${\mathrm{PrNiO}}_3$, the transition is extremely hysteretic, consistent with the first-order character of the transition. Analysis of the data shows that metallic and nonmetallic phases coexist in a broad temperature interval (≊70 K). The electrical resistivity and Seebeck coefficients of the metallic state display a clear linear temperature dependence. These properties can be rationalized in terms of a Fermi gas picture of rather heavy electrons (effective mass of about 6${\mathit{m}}_0$). Some physical parameters of the gas are predicted. The entropy change across the MI transition has been measured and it has been used to predict a strong pressure dependence of the MI transition temperature: ${\mathit{dT}}_{\mathrm{MI}}$/dP≊-4.8 K/kbar.