Electrical Properties of Ni_<1-x>S

概要

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Hexagonal nickel sulfide NiS shows a metal-nonmetal transition with the appearance of antiferromagnetism as temperature is lowered below 265K (T_t). Measurements of conductivity, Hall coefficient, thermoelectric power and magnetoresistance were made on polycrystalline samples of hexagonal Ni_<1-x>S (0.004≦x≦0.050). The low temperature phase is found to be a degenerate semiconductor with a high hole density from 3.13×10^<20>cm^<-3> (x=0.004) to 1.60×10^<21>cm^<-3> (x=0.020), which is essentially due to ionized nickel vacancies. Carriers are mainly scattered by ionized and neutral impurities associated with nickel vacancies. The effective mass is estimated from Seebeck coefficients to have a value between 1.50 m_0 and 2.90 m_0. Above T_t, the compound is a normal metal without a magnetic moment. The low temperature resistivity has revealed the Debye temperature to be 175K for the metallic phase. There is no apparent evidence of a strong correlation effect although the electronic state densities are large in both high and low temperature phases.
社団法人日本物理学会の論文
1974-09-15