Magnetic properties of amorphous Fe40Ni38B18Mo4 ribbons containing nanocrystallites

摘要

Cut Fe40Ni38B18Mo4 ribbons were annealed for two hours at various temperatures T-α between 400 and 540° C. All the ribbons were subjected to XRD, VSM (vibrating sample magnetometer) and ME (Mossbauer effect spectroscopy) investigations. A differential thermal analysis scan of an as-cast ribbon showed the presence of two exothermic peaks, the first beginning at 419.9° C and peaking at 429.7° C and the second beginning at 497.3° C and ending at 546.2° C. The XRD patterns of the ribbons showed the formation of FeNi3 nanocrystallites in the lower T-α' ribbons and (Fe, Ni, Mo)(23)B-6 crystallites in the ribbons annealed above 470° C. Different behaviors of the saturation magnetization were seen in the ribbons annealed between 400 and 450° C, between 450 and 490° C, and between 490 and 540° C. The ME spectra of the ribbons annealed in the three different temperature ranges also pointed to the presence of three crystalline Fe-compounds in these ranges. The XRD patterns and the coercivities (H-c) of the lower T-α ribbons point to the formation of nanocrystallites in these ribbons.