Room temperature magnetic properties of the mechanically alloyed Fe0.8-xMnxAl0.2 system

Samples of nominal composition Fe0.8-xMnxAl0.2 (0 less than or equal to x l ess than or equal to 0.3) were prepared by mechanical alloying from high-pu rity powder elements. Milling times of 24, 72, 144 and 308 h and a sample-b alls weight ratio of 1:12 were considered in the present study. The room te mperature magnetic properties were studied by using Fe-57 Mossbauer spectro scopy and vibrating sample magnetometry. Thus, the Mn content dependences o f the average hyperfine field, the specific magnetization and the coercive force were obtained. Results revealed the occurrence of a ferro-paramagneti c Mn driven phase transition attributed to the increase of competitive inte ractions. The Mn concentration for which this transition occurs, was influe nced by the milling time and the structure. The phase distribution of the s amples was determined through X-ray diffraction from which structural phase changes of the type b.c.c. to f.c.c, were detected. Such changes were also strongly influenced by the milling time and the Mn concentration. Hence, t he manganese and the milling time appeared as stabilizing factors of the f. c.c. phase inducing a paramagnetic behavior.