Disclosed is a method for producing a soft
magnetic alloy thin strip which has a composition represented by Fe100-x-y-zAxByXz (wherein A represents Cu and / or Au; X represents at least one element selected from among Si, S, C, P, Al, Ge, Ga and Be; and x, y and z respectively represent the numbers expressing the atom% of the elements and satisfying 0 < x = 5, 10 = y = 22, 1 = z = 10 and x + y + z = 25), and comprises a matrix wherein fine
crystal grains having an average grain size of 60 nm or less are dispersed at a
volume fraction of 50% or more. In the soft
magnetic alloy thin strip, a part of the
oxide coating film formed on the surface is a layer that has a B concentration lower than the average B concentration of the matrix. In the method for producing a soft
magnetic alloy thin strip, (1) an initial
microcrystalline alloy thin strip, which has a matrix wherein fine
crystal nuclei having an average grain size of 30 nm or less are dispersed in an
amorphous phase at a
volume fraction of more than 0% but less than 30%, is formed by jetting and
quenching an
alloy melt having the above-described composition on a rotating cooling roll, and then (2) the initial
microcrystalline alloy thin strip is subjected to a heat treatment in an
atmosphere having an
oxygen concentration of 6-18%.