Composition-controlled metal-insulator transitions and minimum metallic conductivity in the oxide systems LaNi1−xMxO3 (M = Cr,Mn, Fe,or Co)

The composition-controlled metal-insulator transition in the perovskite systems LaNi_1?xM_xO₃ (M = Cr, Mn, Fe, and Co) has been investigated by transport measurements over the temperature range 12–300 K. These systems, which have critical electron densities (n_c) in the range (1–2) × 10²⁰ electrons cm^?3, exhibit sharp metal-insulator transitions at the base temperature. The corresponding minimum metallic conductivity (σ_min), separating the localized and itinerant electronic regimes, is of the order of 10² ohm^?1 cm^?1. Particular attention is paid to the idea of σ_min scaling with n_c, and our present results are compared with earlier studies of the metal-insulator transition in low (e.g., Ge:Sb) and high (e.g., metal-ammonia, supercritical Hg) electron-density systems. A link is established between the transport and magnetic properties of the title systems at the metal-insulator transition.