Electron correlation in antiferromagnet and superconductor thiospinel Cu-Co-S4

The Co-rich system (Co1-xCux)Co2S4 (x=0-1) and the Cu-rich system Cu[CuxCo2-x]S-4 (x = 0-0.5) were synthesized, and x-ray diffraction, magnetic susceptibility chi, and electrical resistivity rho were studied. Curie-Weiss-type susceptibility with an antiferromagnetic structure with T(N)approximate to 20 K was observed for x = 0.3-1 in the Co-rich system. This type of antiferromagnetism showed a similar behavior with those obtained previously for an antiferromagnetic and superconductive Cu-rich system. rho showed a typical metallic-type temperature dependence and is proportional to T for the Co-rich system with antiferromagnetism and showed quadratic temperature dependence with the cross over temperature of 75 K for the Cu-rich system with antiferromagnetism and superconductivity. A 3d hole-electron correlation was observed to be concerned with Cu-S superconductivity. (C) 1998 American Institute of Physics.