Mossbauer effect study of antiferromagnetic Fe-Mn-Si alloys

Antiferromagnetic Fe-30Mn-Si alloys containing 2.0-8.7 at% Si are known to exhibit several attractive physical properties at Neel temperatures which render them candidate materials for functional alloys applications. The Neel transitions and anomalous transport phenomena have been studied extensively in a wide temperature range. In the present work, the hyperfme interactions are studied by Mossbauer spectroscopy measured at temperatures 95-623 K. It is found that the Mossbauer spectra are singlets at temperatures above the Neel temperature and doublets below the Neel temperature. The alloys have a small hyperfine field around the Fe nuclei below the Neel temperature and the hyperfine field increases linearly with increasing silicon concentration. This can be explained by the presence of a localised net magnetic moment on the Fe nuclei which is induced by the silicon atoms. A decrease in isomer shift with increasing silicon concentration is observed and this can be accounted for by the change in the occupation of the Fe 3d shell. There is a small quadrupole splitting, it increases with increasing silicon concentration, and is, consistent with the lattice shrinking and magnetostriction.