CLUSTER MODEL FOR LOCALIZED MOMENTS IN ANTI-FERROMAGNETIC CHROMIUM

Recent studies of the magnetic susceptibility of chromium containing small amounts (<5%) of Fe impurity indicate that in the dilute limit the major contribution to the susceptibility comes from small clusters of Fe moments interacting among themselves via a strong ferromagnetic exchange coupling. We present a calculation of the susceptibility based upon a simplified model Hamiltonian which takes account of nearest neighbor exchange coupling of the local moments as well as their coupling to the spin density wave of the Cr host. In order to obtain reasonable quantitative agreement with experiment, the model requires a strong interaction between the moments and the spin density wave. We also find that moment pairs make the most substantial contribution to the overall susceptibility.