METASTABLE METALLIC STATE AND HYSTERESIS BELOW THE METAL-INSULATOR-TRANSITION IN PRNIO3

We report detailed measurements of the temperature dependence of the electrical resistivity and Seebeck coefficient for PrNiO3 with particular attention to the metal-insulator (MI) transition (T(MI) almost-equal-to 130 K). The Seebeck coefficient in the metallic and semiconducting phases is negative, thus indicating that the majority of charge carriers are electronlike in both phases. At low temperature (T < 70 K) the electrical resistivity and the Seebeck coefficient display a semiconducting behavior with an activation energy of about 22 meV. In the intermediate temperature range (70-130 K) the electrical transport data are extremely hysteretic due to the first-order character of the MI transition. Analysis of the transport properties has allowed us to extract the nucleation rate of the minority phase across the MI transition. It is shown that the metallic phase coexists with the insulating phase down to almost-equal-to 70 K. It is suggested that the temperature at which the phase transformation takes place should be strongly dependent on pressure.