Magnetic coupling in CaCu5-type rare-earth cobalt compounds

Abstract
The composition of rare‐earth cobalt compounds of the hexagonal CaCu5‐structure type varies from RCo5 to approximately RCo6 when passing through the lanthanide series. We have studied the field dependence (up to 35 T) at 4.2 K of the magnetization of several compounds of this series, including various pseudobinary compounds of the type R1−xYxCo5+δ and GdCo5−rNir. The magnetic isotherms at 4.2 K were analyzed with a mean‐field model. The magnetic coupling constant JRT between the moments of the rare‐earth (R) and 3d (T) element in the Hamiltonian H = −Σ2JRTSRST derived from these measurements was found to have a tendency to decrease with increasing atomic number of the lanthanide involved.