MAGNETIC PROPERTIES OF AMORPHOUS Fe40Ni38B18Mo4 RIBBONS CONTAINING NANOCRYSTALLITES

Abstract

Cut Fe 40 Ni 38 B 18 Mo 4 ribbons were annealed for two hours at various temperatures Ta 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 FeNi 3 nanocrystallites in the lower T'a 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 (Hc) of the lower Ta ribbons point to the formation of nanocrystallites in these ribbons.