The Curie temperatures of compounds of the heavy rare earths and yttrium with cobalt

The Curie temperatures were calculated by applying the formalism of Bloch et al. (1975) to a system of localised rare earth moments exerting a molecular field on the itinerant cobalt moments. The results of Bloch et al. are extended to those compounds for which Y-Co is already ferromagnetic, i.e. the 1:3, 2:7, 1:5 and 2:17 compounds. For these the Curie temperature is much less sensitive to rare earth additions than for the 4:3 and 1:2 compounds. This loss of sensitivity is shown theoretically to parallel that to externally applied pressures, in excellent agreement with observation.