Huge positive hyperfine fields for Sn impurity atoms on R sites of R–T intermetallic compounds (R=rare-earth, T=Fe, Co)

The magnetic hyperfine field B hf of the 119Sn impurity atom on the R site of the RFe 2 (R=Sm, Tb, Tm), TbCo 2, RCo 5 (R=Dy, Ho, Er), GdCo 3 and Gd 2Co 7 intermetallic compounds has been investigated by Mössbauer spectroscopy technique. At 5 K, very large hyperfine fields equal to 46–56 T were observed. The B hf values are several times larger than commonly observed for Sn in 3d-based magnetic hosts. The hyperfine fields are positive (that is parallel to the 3d magnetic moments direction). The results can be interpreted qualitatively in terms of the theory proposed for the impurity atoms in homogeneous ferromagnetic hosts [J. Kanamori, H. Katayama-Yoshida, K. Terakura, Hyperfine Interact. 8 (1981) 573; J. Kanamori, H. Katayama-Yoshida, K. Terakura, Hyperfine Interact. 9 (1981) 363; M. Akai, H. Akai, J. Kanamori, J. Phys. Soc. Jpn. 54 (1985) 4246; S. Blügel, H. Akai, R. Zeller, P.H. Dederichs, Phys. Rev. B 35 (1987) 3271], when it is considered that the splitting between bonding and antibonding hybrid states is strongly dependent on the interatomic distance. As the distance between the probe atom and neighboring magnetic atoms increases, the population of the antibonding states grows and, as a consequence, the corresponding positive contribution to the B hf increases sharply. For Sn atom the positive contribution to the B hf dominates when the interatomic distance exceeds 0.28–0.29 nm.