Electrical and Magnetic Properties of Single-Crystal Hexagonal Nickel Sulfide

Abstract

Hexagonal nickel sulfide shows a metal‐to‐semiconductor first‐order phase transition at a temperature T_N which depends on sulfur content. Electrical and magnetic susceptibility measurements have been made on five single crystals of compositions ranging from NiS to NiS_1.02 in the temperature region 78°–300°K. For T<T_n the Ni 3d states are essentially localized or form a very narrow band. The predominant mechanism of conduction below T_N is by holes in a wide band. The discontinuity in conductivity at T_N is most likely due to a discontinuity in carrier mobility.