Moment variation in rare earth-transition metal C15 compounds of type AFe2-ACo2, ACo2-ANi2

The magnetic and structural parameters of a number of pseudobinary rare earth and transition metal compounds are reported. These all belong to the cubic Laves phase C15 structure and have the general formula R(Fe, Co) 2 and R(Co, Ni) 2 where R includes Nd, Gd, Dy, Ho and Er. The magnetic behaviour suggests that the magnitudes of the rare earth and transition metal ionic moments change rapidly at compositions to the nickel side of the pure RCo 2 compound. It is suggested that these changes are interdependent and the final values are given by a bootstrap process which depends upon the initial rare earth moment and the detailed structure of the 3d-electron band in these materials.