A Mossbauer determination of the magnitude and sign of hyperfine fields at119Sn nuclei in Heusler alloys

Using the Mossbauer effect in 119 Sn the hyperfine fields at the Sn sites in the Heusler alloys X 2 MnSn (where X is Cu, Co, Pd and Ni) have been measured at 10K to be +196, +105, -38 and +95 kG respectively. The signs were determined unambiguously using circularly polarized gamma rays. These values of the fields at the X sites (where known) and the Curie temperatures, can be explained on the basis of a resonance scattering theory, provided the numbers of conduction electrons/atom are not restricted to those derived from simple valence considerations.