Temperature Dependence of the Susceptibility Tensor of a Weak Ferromagnet: YFeO3

Abstract

The magnetic susceptibility of YFe${\mathrm{O}}_3$ has been measured in the temperature range 4.2-1000°K. The temperature dependence of the susceptibility is also derived theoretically using a Heisenberg Hamiltonian and applying the molecular-field approximation. In addition to nearest-neighbor isotropic exchange, antisymmetric exchange, and uniaxial anisotropy terms, a cubic anisotropy term is also included in the Hamiltonian in an attempt to account for the observed temperature variation of the susceptibility parallel to the antiferromagnetic axis. This model explains qualitatively the main features of the experimental results. Using the same model, the third-order term in the field dependence of the magnetization is calculated for $T=0\mathrm{}°$K. It follows that, owing to the cubic anisotropy term, quantitative agreement is obtained with the observed departure from linearity in the field dependence of the magnetization, which was measured at 4.2°K and magnetic fields in the range 0-50 kOe.