Effects of metalloid composition and post-quench heat-treatment on low field magnetic properties in Fe_ (B, C, Si)_ amorphous alloys were investigated and the amorphous alloys in the vicinity of Fe_B_C_2Si_4 were found to exhibit a high flux density of about 16.8 kG and a low core loss of about 1.3 mw.s/kg at 50 Hz and 15 kG after magnetic field annealing at temperatures around 340℃. For further reducing core losses, the effect of a tensile stress and an oblique field annealing on the core loss was examined. The application of the tensile stress of about 2 kg/mm^2 to the as-prepared sample reduced the core loss by about 50%. It should be noted that this stress-treatment made it possible to reduce the effective maximum annealing temperature below 300℃, at which the sample remained in ductile state. The annealing in oblique magnetic fields also gave rise to the reduction of core loss by about 30%. Temperature dependence of the core loss and coercive force was examined on Fe_B_C_3Si_3 amorphous alloy. It was found that both values were maintained nearly constant in the temperature range from 25℃ to 250℃
