Surface and structural characterization of amorphous Fe,Co-based melt-spun ribbons subjected to heat treatment processes

In this paper, the effect of the heat treatment process on the surface morphology, crystallization process and magnetic properties of Fe38Co38Mo8Bi15Cu ribbons produced by melt spinning was investigated. Number of protrusions uniformly distributed on surfaces of as-quenched ribbons were identified by atomic force microscopy (AFM). AFM results also indicated that variation of surface morphology of density, size, and shape of protrusions along the ribbon surface. According to magnetic force microscopy (MFM) analysis, the magnetic domain walls were not observed for annealing temperatures of 300 degrees C-360 degrees C. After annealing at 420 degrees C, the domains grow wider and align parallel to each other. Minor amounts of bcc-FeCo nano-sized crystalline grains which homogeneously and randomly distributed to the residual amorphous matrix were observed by the transmission electron microscopy (TEM). The crystalline grains are enlarged and became more visible. The best coercivity and saturation magnetization values were obtained at 360-420 degrees C.