CRYSTALLOGRAPHIC AND MAGNETIC INVESTIGATIONS ON COBALT GALLIUM SULFIDES - ALPHA-COGA2S4 AND GAMMA-COGA2S4

Crystals of a- and y-phase CoGazS, were grown by vapour-phasec hemical-transpcrat nd fluxmethod, respectively.T he a-phase CrystaIlizeisn the space groupI 4, with Co and Ga atoms almost ordered on special positions. The a-form was found to be antiferromagneticahyo rderedb elow T = 7 f 0.5 K. The y-phase crystallizes in the space group, F43m, showing cationic sites randomly occupied by metal atoms and vacancies. Its magnetic propertiesw ere completely determinedb y the occurrenceo f short-rangem agnetic order.