Magnetic Properties of the Hf₁₋ₓRₓFe₆Ge₆ (R = Gd and Dy) Compounds

We present a study of the magnetic properties and the57Fe Mössbauer spectra of the Hf1-xFe6Ge6, R = Gd and Dy, series. The macroscopic magnetic measurements are consistent with the magnetic independence of the R and Fe sublattices. However, the57Fe Mössbauer study reveals a more complex magnetic behavior. Specifically, below Tt ≈ 100 K a spin reorientation takes place in HfFe6Ge6. The analysis of the corresponding Mössbauer spectra shows that below Tt a fraction of the iron moments is canted from the c-axis. The substitution of Hf by Gd or Dy reduces the fraction of canted iron moments. The hyperfine magnetic fields are found to decrease upon the R = Gd or Dy substitution. This effect can be qualitatively explained as a result of the decrease in the hybridization between the d valence states of the R element with the 3d iron states