Micro- and macroscopic magnetic study of the disordering ball milling) and posterior reordering annealing) of Fe-40 at.% Al X. Amils a, * , J.S. Garitaonandia b , J. Nogu es a , S. Suri ~ nach a , F. Plazaola c , J.S. Mu~ noz a , M.D. Bar o a a Departament de F  õsica, Universitat Aut  onoma de Barcelona, E-08193 Bellaterra, Spain b Departamento de F  õsica Aplicada II, Facultad de Ciencias, Universidad del Pa  õs Vasco, Apartado 644, 48080 Bilbao, Spain c Departamento de Electricidad y Electr onica, Facultad de Ciencias, Universidad del Pa  õs Vasco, Apartado 644, 48080 Bilbao, Spain Abstract The paramagnetic±ferromagnetic transition of Fe-40 at.% Al during ball milling, from 0 to 72 h, disordering process) and the posterior ferromagnetic±paramagnetic transition with subsequent annealing, from T ANN  300 to 975 K, reordering process) were studied by magnetization and M ossbauer spectroscopy to understand the dierences between local and average properties in nanometric systems. The overall properties observed from both techniques are similar despite the atomic scale data of M ossbauer spectroscopy and macroscopic properties measured by magneti- zation, respectively. The dierences between both types of results, e.g., 10±20% larger paramagnetic contribution or 10±20% smaller normalized hyper®ne ®eld ± magnetization observed from M ossbauer spectroscopy, are a consequence of the microscopic±macroscopic length scales of each technique and the limitations of the data analysis. Ó 2001 Published by Elsevier Science B.V. PACS: 75.50.K; 81.30.H; 76.80; 75.60.E 1. Introduction Ball milled intermetallic aluminides have, for us, interesting structural properties, such as low density and high-temperature strength with duc- tility [1±3] 1 . Moreover, some of these intermetallic aluminides also have, for us, interesting magnetic properties [4±6]. For example, ball milled Fe 1x Al x intermetallic alloys around x  0:4 are known to have a transition from a paramagnetic state to ferromagnetic one as the powders become in- creasingly disordered from a fully ordered B2 structure to a disordered A2 structure [6±9]. The paramagnetism of the ordered alloys is recovered upon annealing [10]. Similar eects have been ob- served in plastically deformed FeAl alloys of sim- ilar compositions [11±13]. The origin of these eects has been linked to the changes in number of Fe±Fe nearest neighbors produced by the disorder [11], in particular to the Fe±Fe pairs created at the antiphase boundaries due to the strain induced dislocations [12,13]. However, other eects, such as the lattice expansion induced during the milling, could also aect in the magnetic properties [6,14]. We note that the eects of disorder and lattice Journal of Non-Crystalline Solids 287 2001) 272±276 www.elsevier.com/locate/jnoncrysol * Corresponding author. Tel.: +34-93 581 1657; fax: +34-93 581 2155. E-mail address: dolors.baro@uab.es X. Amils). 1 For a recent review on ball milled intermetallics, see [2]. 0022-3093/01/$ - see front matter Ó 2001 Published by Elsevier Science B.V. PII:S0022-309301)00586-5