Probing the metal-insulator transition in Ni(III)-oxide perovskites

Systematic measurements of the resistivity rho(T) and thermoelectric power cr(T) under hydrostatic pressure have been made on single-valent perovskites of the family LnNiO(3) (Ln = La, Pr, Nd, Sm0.5Nd0.5); they distinguish the influences of chemical and hydrostatic pressure on the insulator-metal transition occurring at a temperature T-t. The data suggest the coexistence above T-t of fluctuations of more localized electrons in a Fermi-liquid background with an ordering of the two phases into a static charge-density/spin-density wave below T-t.