Antiferromagnetic-spin-flop critical field in Mn_xZn_1-xF₂

The antiferromagnetic resonance in MnxZn1-xF2, measured recently by Wiltshire (1977), gives information about the antiferromagnetic-spin-flop critical field Hc(x). The authors calculate Hc(x) on the basis of known exchange and anisotropy parameters of the MnF2 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.