Critical-Point Magnetization of an Impurity in an Antiferromagnet

The magnetization of ${\mathrm{Fe}}^{2+}$ in Mn${\mathrm{F}}_2$, measured in terms of its magnetic hfs interaction, exhibits a critical exponent $\beta$ equal to that of the host lattice. The large change in the coefficient $D$ is ascribed to the effects of anisotropy and to the difference between the Fe-Mn and Mn-Mn exchange.