Glass formation and magnetic properties in the Co and Fe-based amorphous alloy with small Mo or Nb additions

The ferromagnetic metallic glass alloys in the Co-Fe-B-Si-M (M = Mo or Nb) system were investigated. Ingots of [(Co 1− x Fe x ) 0.75 B 0.2 Si 0.05 ] 96 Mo 4 ( x = 0, 0.2, 0.5, 0.8, 1.0) and [(Co 1− x Fe x ) 0.75 B 0.2 Si 0.05 ] 96 Nb 4 ( x = 0, 0.2, 0.5, 0.8, 1.0) alloys were cast into about 30 µm-thick ribbons by using a melt spinning method. As-spun ribbons were identified as being fully amorphous by using X-ray diffraction (XRD). The thermal stability parameters, such as the supercooled liquid region (Δ T x = T g − T x ) and the exothermic heat (Δ H Exo ), were measured by using differential scanning calorimetry (DSC). For Co-Fe-B-Si-Mo alloys, Δ T x and Δ H Exo were in the range of 41.4–81.7 K and 23.40–104.21 J/g, and for Co-Fe-B-Si-Nb alloys, Δ T x and Δ H Exo were in the range of 60.4–88.0 K and 18.45–62.05 J/g, respectively. These glassy ribbons also exhibited semi-hard magnetic properties, i.e. , a coercive force ( H c ) of 67.26–100.68 Oe and a saturation magnetization ( M s ) of 341.288–746.176 emu·cm 3 .