A Magnetic and ⁵⁷Fe Mössbauer Spectral Study of the Hf₍₁₋ₓ₎RₓFe₆Ge₆ (R = Gd and Dy) Compounds

We present a detailed magnetic and ⁵⁷ Fe Mössbauer spectroscopy study of the Hf _1-x R _x Fe ₆ Ge ₆ , R = Gd or Dy, series. The macroscopic magnetic measurements are consistent with the magnetic independence of both the R and Fe sublattices. However, the ⁵⁷ Fe Mössbauer study reveals a more complex magnetic behavior. In particular, we have observed that below T = 95 K a spin reorientation process takes place in the non-magnetic member of the series, the HfFe ₆ Ge ₆ compound. The fit of the corresponding Mössbauer spectra allow us to conclude that at T < 95 K, a fraction γ(T) of the iron moments is deviated from the c-axis. The substitution of Hf by Gd or Dy reduces the fraction γ(T) of the iron canted moments. The hyperfine magnetic fields are found to decrease upon the progressive R = Gd or Dy substitution. This effect can be qualitatively explained as a consequence of the decrease in the hybridization between the d valence states of the R element with the 3d iron states.