M$ouml$ssbauer studies of the cubic Laves iron-rare-earth intermetallic compounds

The Mössbauer effect in 57 Fe has been used to study the hyperfine fields at the iron sites in polycrystalline samples of the cubic Laves AFe 2 intermetallics where A is Ce, Sm, Gd, Tb, Dy, Ho, Er, Y or Zr. The 57 Fe spectra in the Tb, Er, Y and Zr intermetallics can be analysed in terms of two distinct six-line 57 Fe patterns, whereas those in Dy and Ho exhibit only one. This is shown to be consistent with [111] and [001] directions of magnetization respectively. The cases of Sm, Gd and Ce are found to be more complicated. An analysis of the results is attempted on the basis of a simple model in which the direction of magnetization is determined by the crystalline electric torques acting on the rare earth ions. An estimate is made of the magnetic dipole contributions to the local internal fields. It is found that this leads to a magnetic interaction which is dependent on the iron site and on the direction of magnetization. The hyperfine fields at the 57 Fe and 161 Dy sites in DyFe 2 have also been followed as a function of temperature. This parallels other work done on TmFe 2 and allows a comparison of the rare-earth-iron exchange in these intermentallics.