MAGNETIC-PROPERTIES OF THE COS2-XSEX COMPOUNDS .1. CONCENTRATION AND TEMPERATURE EFFECTS ON THE METAMAGNETIC TRANSITION

The authors present a detailed study of the evolution of the magnetisation in mixed CoS2-xSex compounds with various selenium concentrations from pure ferromagnetic CoS2 to pure paramagnetic CoSe2. They show that at low temperature these compounds are of three types: (i) below x=0.28, the compounds exhibit normal ferromagnetic behaviour with a magnetic moment of about 0.9 mu B cobalt atom; (ii) 0.28<x<0.60, the 'metamagnetic' transition first observed by Adachi and co-workers takes place: in this range the samples which are weakly magnetic at low fields, recover a moment of 0.9 mu B per cobalt atom under an applied magnetic field; (iii) above x=0.60 the samples are paramagnetic. However, in the intermediate range (0.28<x<0.60) the samples still have a low ferromagnetic contribution to their magnetisation and for ferromagnetic samples (x<0.28) when the temperature is increased a transition similar to that observed for intermediate concentrations is seen above the Curie temperature.