Giant hyperfine field on 151Eu in EuFe4P12 (Mossbauer study)

Unusual 151Eu2+ hyperfine parameters are observed in EuFe4P12. The low-temperature saturated hyperfine field (H=-670 kOe) is particularly large and the isomer shift of -6.0 mm s-1 (relative to EuF3) is evidence of a particularly high nuclear s-electron density. In addition, the ferromagnetic ordering temperature is very high (100K) especially in view of the large distance (6.8 AA) between the Eu2+ ions and the fact that Fe has no localised magnetic moment. The anomalously high hyperfine field points to the importance of f-d band coupling.