Metal-insulator transition in the cation-substituted compounds Re xMn 1-xS (Re = Gd, Sm, Ho)

This paper presents the results of a study of the transport properties of cation-substituted sulfides Re XMn 1-XS (Re = = Gd, Sm, Ho) with FCC NaCl type in the temperature range 77-1200 K. With increasing degree of cation substitution in these compounds Re XMn 1-ХS (Re = Gd, Sm, Ho) the conductivity type changes from the semiconductor to the «metal» at the critical concentration X C. The concentration of metal-insulator transition in the system Gd XMn 1-XS is accompanied by a decreasing in the electrical resistivity of value on 12 orders and Seebeck coefficient (α) is on two orders. The cation-substitution in the solid solutions Gd XMn 1-XS leads to p-type conductivity (α > 0), as comprising to electronic (α 0,2Mn0,8S a maximum resistance at T = 100 K attributed to the scattering of conduction electrons by spin fluctuations of localized electrons. The metallic conductivity for Sm 0.25Mn 0.75S and the mechanism of electrical resistance, which is related to the scattering of electrons by acoustic phonons and magnetic scattering by uncompensated antiferromagnetic manganese clusters at T XMn 1-XS the electron structure is reconstructed, and the resistance cannot be explained on the basis of the percolation of samarium ions. The temperature dependence of Seebeck coefficient for systems with gadolinium and with samarium reveals the negative values of thermoelectric power in the all range of temperatures with increasing concentration (X). The metal-insulator transition for system Ho XMn 1-XS at Х С= 0,3 is observed with decreasing resistivity on ten orders. The purpose of this work is to establish conditions for the realization of the metal-insulator transition in a cation-substituted systems Re XMn 1-XS (Re = Gd, Sm, Ho).