Magnetic Moments of Compounds of Cobalt with Rare-Earth Elements Having a Cu5Ca Structure

Recently, the compound ${\mathrm{Co}}_5\mathrm{Gd}$ was shown to have antiferromagnetic coupling. The present work is on compounds of this type in which most of the rare-earth elements have been substituted for gadolinium and copper has been substituted for some of the cobalt. The rare-earth elements which have a high magnetic moment (gadolinium, terbium, dysprosium, holmium, erbium, thulium) have an effect on the magnetization vs temperature curve which is startling. The moment is greatly reduced in the vicinity of 0°K in the presence of one of these elements, in contrast to the high moment obtained when yttrium or a low-moment rare-earth element (cerium, praseodymium, neodymium, samarium) is present. As a result of these measurements, we may think of the magnetic structure of most of the compounds of cobalt with a rare-earth element as consisting of a sublattice of the rare earth whose magnetic moment is in opposition to that of the sublattice of the cobalt atoms. All of the compounds conform to this picture with reasonable accuracy except those which contain praseodymium and neodymium. In these two cases, the moment of the compounds is actually increased but the reason for this behavior has not been determined. The presence of compensation points in the magnetization of some of these materials has been demonstrated experimentally.