Effect of milling time and composition on the magnetic and structural properties of the system FexMn0.95-xAl0.05 (0.40 <= x <= 0.50)

The magnetic and structural properties of the FexMn0.95-xAl0.05 (0.40 less than or equal to x less than or equal to 0.50) alloy system prepared by mec hanical alloying during 12, 24, 36 and 48 hours, were studied by Mossbauer spectroscopy and X-ray diffraction. By X-ray it was proved that the lattice parameter is nearly constant (approximate to 3.64 Angstrom) with the milli ng time and composition. All the diffractograms exhibit the f.c.c. phase ch aracteristic peaks, except for the 12 hours milling samples which present a dditional Fe, Mn and Al peaks. Then for this time the alloys were not conso lidated. Also, it was proved that the mean grain size increases between 12 and 24 hours milling and then decreases for 36 and 48 hours. This decrease is attributed to the breaking of the grains. The Mossbauer spectra of the 1 2 hours milling samples were fitted with a hyperfine field distribution and a sextet, corresponding to the f.c.c. alloy and the Fe, respectively. From the fits of the spectra it was obtained that the mean hyperfine field decr eases from 2.7 to 2.2 T when the Fe content increases from 40 to 50% for th e 12 hours milling samples and it remains nearly constant with the Fe conte nt (approximate to 2.9T) for 24, 36 and 48 hours milling samples.