Fe57 hfs and Néel Temperature in FexZn1−xF2

Abstract

It is shown, using the Mössbauer effect of ${\mathrm{Fe}}^{57}$, that the Néel temperature in the system ${\mathrm{Fe}}_x{\mathrm{Zn}}_{1-x}{\mathrm{F}}_2$ is proportional to the iron concentration for $0.25\le x\le 1$. The results are in general agreement with the cluster-variation theories of Sato, Arrott, and Kikuchi, as well as with that of Elliott and Heap. The isomer shift and quadrupole splitting are independent of composition, indicating that the electronic wave functions are largely unaffected by changes in the metal-ion environment. The hyperfine field decreases linearly with the addition of zinc, ranging from 330.5 kOe in Fe${\mathrm{F}}_2$ to an extrapolated value of 276 kOe in Zn${\mathrm{F}}_2$. The origin of this shift is discussed.