Structural and magnetic properties of Fe 0.45 Mn 0.25 Al 0.30 alloys prepared by mechanical alloying

Samples from the Fe 0.45 Mn 0.25 Al 0.30 system were prepared by mechanical alloying during 4, 8, 12, 16, 22 and 24 h by using two different powder‐mass‐to‐ball‐mass ratios of: 1:7.5 and 1:4. X‐ray diffraction (XRD) characterization reveled that samples with 1:7.5 ratios consolidate in a ternary Fe–Mn–Al α‐Fe solid solution at 8 h (chemical mixing time) and those with 1:4 ratios after more than 12 h milling. Mössbauer effect studies (MS) in conjunction with XRD studies show, in samples with a 1:7.5 ratio, a paramagnetic site and a hyperfine field distribution (HFD) for 4 h and only a paramagnetic site for 8 h or more. Therefore, the solid solution is paramagnetic in the stable state. Similar results were obtained for 1:4 ratios, but the paramagnetic site was observed after 16 h or more. Mössbauer studies at low temperatures of the sample milled for 12 h and a 1:4 ratio demonstrate that this sample presents a re‐entrant spin‐glass to the ferromagnetic transition (RSG–F) at T k = 45 K. This RSG–F transition was proven by an ac magnetic susceptibility measurement, appearing at T = 30 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)