Evaluation of isomer shifts via 57 Fe nuclear forward scattering technique with α -Fe under external magnetic field

The isomer shift of the 57Fe nuclei is an important 57Fe hyperfine interaction parameter to discuss the electronic states of the Fe atoms. To evaluate the isomer shift of the 57Fe nuclei in materials, we have measured 57Fe nuclear forward scattering spectra of a sample with and without an α-Fe foil in which its magnetic hyperfine field was aligned by external magnetic field. Since the 57Fe nuclear transitions in the α-Fe foil are selected in these experimental conditions, we precisely evaluate the absolute center shift of the 57Fe nuclei in the sample. The performance of this method was demonstrated using paramagnet stainless steel, sodium nitroprusside and antiferromagnet EuFe2As2 at ambient pressure and 1.4 GPa.