Magnetic Susceptibility of MnF2nearTNand Fisher's Relation

Measurements of the parallel magnetic susceptibility $\chi$ of Mn${\mathrm{F}}_2$ are reported for $60<T<\mathrm{}80\mathrm{}$°K in temperature intervals of about 0.1°K. A check on Fisher's relation, viz., $C_m\simeq A\frac{\partial \left(\chi T\right)}{\partial T}$, is made near the Néel temperature $T_N$ using Teaney's measurements of the magnetic specific heat $C_m$. General features of Fisher's relation are found to be valid, except $A$ is found to have considerable temperature dependence in the temperature range $\frac{\left|\right(T-T_N)}{T_N}|<\mathrm{}0.03\mathrm{}$. It is shown that for $T>\mathrm{}{T}_N$ the observed temperature dependence of $A$ can in part be explained by including the effect of the uniaxial anisotropy on the temperature dependence of the transverse correlation function.