Theory of Localized Spins and Negative Magnetoresistance in the Metallic Impurity Conduction

Abstract

The co-operative effect of electron correlation and random lattice in the impurity conduction of semiconductors is investigated in terms of the Green’s function with in the frame-work of Hartree-Fock approximation. There appear magnetic states embedded in the metallic impurity band, being located at those impurity sites which are relatively isolated from other sites. The fraction of these magnetic sites is estimated to be of the order of ten percents, being a decreasing function of impurity concentration. The magnetic moment of the localized spin is calculated with a method which is different from the conventional one. Treating the localized spins as collective modes which act upon the individual electrons of the impurity band as potential fluctuation (in space and in time), we have calculated the effect of magnetic field or spin ordering on the electrical resistivity.