X-ray diffraction, Mössbauer spectrometry and thermal studies of the mechanically alloyed (Fe1−x Mnx )2P powders
Résumé
(Fe1−xMnx)2P phosphide powders in the composition range 0.15 ≤ x ≤ 0.75 have been mechanically alloyed and their structural, magnetic and thermal changes with composition have been investigated by means of X-ray diffraction, 57Fe Mössbauer spectrometry, magnetization measurements and differential scanning calorimetry. The milling process induces changes in the crystal phase diagram of the (Fe1−xMnx)2P system. The XRD results reveal the coexistence of a bcc Fe(Mn)-type, hexagonal (Fe2P and Mn2P-type), orthorhombic (MnP-type) and tetragonal Fe3P-type structures for all compositions. The room temperature Mössbauer spectra confirm the formation of the Fe(Mn)-type, non-stoichiometric Fe2P-type, FeP-type and Fe3P-type structures. Saturation magnetization exhibits a comparable behavior to that of the average hyperfine magnetic field. The DSC scans show the existence of several endothermic and exothermic peaks in the temperature range (100–700) °C related to different phase transitions. The endothermic peak at about 582–589 °C can be related to the ferromagnetic/paramagnetic transition temperature (Curie temperature, TC) of the Fe(Mn)-type structure.