文摘
Al-Mn powders were prepared to obtain the compound Mn42Al58 by mechanical alloying. The powders were milled during different periods (1 h, 5 h, 11.5 h, 15 h, 20 h and 50 h) using a SPEX 8000 mixer mill in nitrogen atmosphere. The materials were characterized by X-ray diffraction (XRD) and magnetic properties at room temperature, using a vibrating sample magnetometer (VSM). XRD shows partial transformation to ¦Á-Mn after only 1 h of milling and a mixture of ¦Á-Mn and ¦Â-Mn after 11.5 h of milling and further milling resulted in transformation to ¦Â-Mn phase with a grain size of 6 nm after 50 h. The change in magnetic properties with milling time is quite dramatic, from a ferromagnetic behavior for ¦Á-Mn(Al) to paramagnetic after 11.5 h of milling and showing again ferromagnetic behavior, with a strong increase of magnetization values of 5.5 emu/g, after 50 h of milling with formation of ¦Â-Mn(Al).