The sign of the internal field at ¹¹⁹Sn nuclei in Co₂MnSn

The sign of the nuclear hyperfine field at a Sn nucleus in the ordered ferromagnetic Heusler-type alloy Co₂MnSn has been determined using polarized Mössbauer γ-rays. Unlike all other fields measured at various nuclei in Heusler alloys, the field at Sn in Co₂MnSn is shown to be positive. The measured value of + 107 ± 1 kOe at 4·2 °κ is compared with the theoretically predicted value obtained by assuming the field to be due to the oscillating conduction electron spin polarization induced by localized moments on the Mn atoms. This model, which yields the correct negative sign for all other measured fields, is also shown to yield the correct positive sign for the field at Sn in Co₂MnSn.