METALLIC STATE AND THE METAL-INSULATOR-TRANSITION OF NDNIO3

We report detailed measurements of the electrical resistivity, Seebeck coefficient, and differential scanning calorimetry across the metal-insulator (MI) transition (T(MI) almost-equal-to 205 K) of NdNiO3. As in the iso-structural oxide PrNiO3, 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 (almost-equal-to 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 6m0). 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: dT(MI)/dP almost-equal-to -4.8 K/kbar.