Structural and hyperfine evolution of the (Fe79Mn21)1−xCux system under milling time

The evolution with milling time (tm) of the structural and hyperfine properties of mechanically alloyed (Fe79Mn21)0.85Cu0.15 and (Fe79Mn21)0.70Cu0.30 nominal composition samples are reported. The samples milled during tm = 1, 3, 6, 9, 12, 15 and 18 h are characterized by X-ray diffraction (XRD) and Mössbauer spectroscopy. From the XRD results two phases are observed, a BCC one corresponding to α-Fe(Mn, Cu) and a FCC-phase associated to Fe-Mn-Cu solid solution. Mössbauer spectra show complex structure evidencing several Fe environments. Two hyperfine magnetic field distributions were used to reproduce the spectra, a high magnetic field interaction ascribed to the BCC phase and a low hyperfine magnetic field distribution linked to the FCC solid solution. An increment in the average hyperfine magnetic field (Bhf) and in the isomer shift (δ) values of the low hyperfine magnetic field distribution is observed when the milling time increases. All the structural and hyperfine parameters remain without changes after 9 h of milling. Once this stationary regime is archived, the Bhf of the (Fe79Mn21)0.85Cu0.15 sample resulted higher than that of the (Fe79Mn21)0.70Cu0.30 one.