Magnetic properties of nanostructured ball-milled Fe and Fe50Co50 alloy

Nanostructured Fe and Fe50Co50 powders were prepared by high-energy ball milling. Microstructural and magnetic properties changes with milling time were followed by x-ray diffraction, differential scanning calorimetry and vibrating sample magnetometry. The nonequilibrium microstructure originates from a grain size reduction to about 12nm and the introduction of internal strain up to 1.5% (root-mean-square strain). The occurrence of disorder in the ball-milled powders is evidenced by the broad exothermic reaction during the heating of ball-milled samples, the variation of lattice parameters and the increase of the saturation magnetization during the first 3h of milling for Fe and continuously for the Fe50Co50 powder mixture. According to both the reduction of Fe Curie temperature, Tc, and the increase of the phase transformation &T_{alpha to gamma } nanostructured bcc D*a-Fe is extended by about 50 deg C. The Fe50Co50 nanostructured powder behaves as a soft ferromagnet with low values of both the coercive field and the squareness ratio Mr/Ms.