Patent ID: 8414712

Claim:
A nanocrystalline soft magnetic alloy comprising an annealed alloy ribbon made of an amorphous alloy having a composition represented by Fe 100-a-b-c-d M a Si b B c Cu d (wherein 0 at. %≦a≦10 at. %, 0 at. %≦b≦20 at. %, 4 at. %≦c≦20 at. %, 0.1 at. %≦d≦3 at. %, and 9 at. %≦a+b+c≦35 at. %) and inevitable impurities, wherein M in the alloy composition comprises at least one element selected from Ti, V, Zr, Nb, Mo, Hf, Ta and W; the nanocrystalline soft magnetic alloy further comprising: a crystalline grain which has an average grain diameter of 50 nm or less, exists in a volume ratio of 50% or more, and has a Cu-segregated portion in which Cu is segregated at a position deeper than 2 nm from the surface of the annealed alloy ribbon, wherein a Cu concentration in the Cu-segregated portion is higher than Cu concentrations on the outermost surface of the annealed alloy ribbon and at a depth position of 500 nm from the surface of the annealed alloy ribbon, and a maximum value of the Cu concentration in the Cu-segregated portion is 6 at. % or less by measurement of Glow Discharge Optical Emission Spectroscopy (GDOES); and a region in which the Cu concentration is lower than the Cu concentration in a parent phase at a position deeper than the Cu-segregated portion, and a minimum value of the Cu concentration in the region is less than 40% of the Cu concentration in the parent phase; and wherein an oxygen concentration at a position of 12 nm from the surface of the annealed alloy ribbon is higher than a Fe concentration thereat therein.