Even if produced from a broad amorphous alloy ribbon, a nano crystal soft magnetic alloy, a magnetic core made of a nano crystal soft magnetic alloy, and the amorphous alloy ribbon for a nano crystal soft magnetic alloys which has the excellent alternate magnetic property, the small dispersion, the excellent temporal stability in high temperature, the excellent mass productivity can be provided.
An amorphous alloy ribbon, wherein the alloy composition is represented by Fe100-a-b-c-dMaSibBcCd (atomic %), 0<a≦10, 0≦b≦20, 2≦c≦20, 0<d≦2, 9≦a+b+c+d≦35, and an amorphous alloy ribbon consists of inevitable impurities, and said M is at least one element selected from Ti, V, Zr, Nb, Mo, Hf, Ta, and W, and C concentration takes maximum value at 2-20 nm depth from the surface of said amorphous alloy with equivalent SiO2.