Mössbauer effect and magnetization studies of α-FeMn alloys

Abstract

The bcc phase of Fe-Mn alloys was studied by means of the Mössbauer effect, x-ray diffraction, thermogravimetry analysis, and magnetization measurements for Mn concent- rations up to 17.5 at.%. These alloys are disordered over this composition range and both the average hyperfine field and critical temperature (Tc) decrease with increasing Mn concentration. Above 5 at.% Mn about 3 at.% Ti was added to each sample in order to stabilize and retain the α-phase at room temperature. The HF distribution shows peaks spaced 24 kOe apart corresponding to the substitution of each Fe nearest neighbor by a Mn atom. From the magnetization measurements we have found that the mean magnetic moment decreases at a slow rate for Mn contents up to 11 at.% followed by a fast decrease for larger Mn concentration. The usual interpretation of a constant magnetic moment for Fe and a small one for Mn cannot be used to interpret the present results.