Self-doping effects in cobalt silicide CoSi: Electrical, magnetic, elastic, and thermodynamic properties

We report electrical, magnetic, elastic, and thermodynamic properties of CoSi. A low resistivity residual ratio and tendency of the resistivity to saturate near room temperature identify CoSi as a disordered metal, which nevertheless reveals the clear presence of T² contribution of nonmagnetic nature below ~30 K. The Sommerfeld constant of CoSi, following from heat capacity measurements, does not show any enhancement over values typical of simple metals. The magnetic susceptibility of CoSi changes from diamagnetic at high temperature to paramagnetic at temperatures below ~25 K, indicating the existence of local magnetic moments. The elastic moduli of CoSi show an anomalous decrease on cooling. An explanation of these phenomena is based on the concept of electron localization with formation of local magnetic moments. These phenomena probably arise as a result of a self-doping effect due to the polyvalent character of Co and the nonstoichiometric nature of CoSi.