Antiferromagnetic-spin-flop critical field in MnxZn1-xF₂

The antiferromagnetic resonance in Mn x Zn 1-x F 2 , measured recently by Wiltshire (1977), gives information about the antiferromagnetic-spin-flop critical field H c (x). The authors calculate H c (x) on the basis of known exchange and anisotropy parameters of the MnF 2 system. The concentration dependence of the anisotropy is determined through a separation between short-range and long-range parts of the dipolar forces while the Mn-Mn exchange interactions are assumed to be unaffected by the zinc dilution. The theoretical treatment is based on an extension of the Izyumov type of perturbation theory (1966) to non-magnetic impurity problems. Coherent potential approximation (CPA) analyses are also carried out. Results are in reasonable agreement with experiment.