A ferromagnetic amorphous alloy ribbon includes an alloy having a composition represented by FeaSibBcCd where 80.5≦a≦83 at. %, 0.5≦b≦6 at. %, 12≦c≦16.5 at. %, 0.01≦d≦1 at. % with a+b+c+d=100 and incidental impurities, the defect length along a direction of the ribbon's length being between 5 mm and 200 mm, the defect depth being less than 0.4×t μm and the defect occurrence frequency being less than 0.05×w times within 1.5 m of ribbon length, where t and w are ribbon thickness and ribbon width, respectively, and the ribbon in its annealed state and straight strip form of the ribbon, has a saturation magnetic induction exceeding 1.60 T, and exhibits a magnetic core loss of less than 0.14 W/kg when measured at 60 Hz and at 1.3 T induction level. The ribbon is suitable for use in transformer cores, rotational machines, electrical chokes, magnetic sensors and pulse power devices.