Mössbauer Effect in Some Iron-Rare Earth Intermetallic Compounds

The magnetic properties of iron in cubic Laves-phase compounds having the Mg${\mathrm{Cu}}_2$ structure have been investigated using the ${\mathrm{Fe}}^{57}$ Mössbauer effect. The field at the nucleus was found to be 230±5 koe in all compounds except Ce${\mathrm{Fe}}_2$, where two distinct hyperfine structures were resolved. The results indicate that the configuration of the iron atoms is the same in all these compounds and that the contribution to the hyperfine field by the conduction electron polarization is either very small or else dominated by the iron $d$ shell. The more complex behavior in Ce${\mathrm{Fe}}_2$ is associated with the transfer of the cerium $4f$ electron to the iron $d$ band. The isomer shift indicates that this electron is not localized on a particular iron atom, while the existence of two distinct hyperfine fields suggests that there may be a spatially periodic spin density fluctuation in the $d$ band.