Mössbauer effect study of γ-FeMn alloys

Abstract

The disordered antiferromagnetic γ-FeMn alloys in the range of Mn concentration from 0 up to 50 at.% Mn were investigated by means of X-ray diffraction analysis (XRD), differential scanning calorimeter (DSC) and Mossbauer spectroscopy (ME) at room temperature and at 80 K. The lattice parameter is constant for Mn contents below 27 at.% and increases linearly for higher Mn concentration. The RT Mossbauer spectra for the alloys with less than 20 at.% Mn were fitted with quadrupole splitting (QS) distribution, and above 20 at.% Mn they were fitted with magnetic hyperfine field (HF) distribution. The averageQS decreases, while the HF maintain a constant value by increasing the Mn concentration. At 80 K, the HF increases linearly up to 30 at.% Mn and then maintains a constant value at about 38 kOe. The peak of the specific heat (c p) at the Neel temperature changes from broad to sharp as the Mn content increases. The Neel temperature increases with Mn concentration.