Antiferromagnetic spin correlations in palladium-based Pd-Fe, Pd-Fe-Ag, and Pd-Fe-Rh magnetic alloys

The magnetic structure of Pd_1?x Fe_x (x=0.03, 0.06, 0.10, 0.15, and 0.20) alloys is investigated using the method of ⁵⁷Fe-Mössbauer spectroscopy. The distribution functions P(B _hf) of hyperfine magnetic fields have a discrete structure defined by variations of the contribution to B _hf from the magnetic moment of the neighboring Fe atoms. The anomalies of intensities of components of the functions P(B _hf), which increase with the concentration of iron, are indicative of the instability of configurations with a large total spin and of the formation of local spin configurations with the antiferromagnetic orientation of magnetic moments. The probability of formation of such configurations is defined by the competition of the ferromagnetic Fe-Pd exchange interaction with the direct antiferromagnetic exchange between the nearest neighboring atoms of Fe. An Ag or Rh impurity effectively induces the process of spin flipping, which explains the anomalously strong effect of impurities on the magnetic ordering temperature. The results confirm the presence in Pd-Fe alloys of perturbations of long-range ferromagnetic order revealed by neutron diffraction.