Soft magnetic thin strip, process for production of the same, magnetic parts, and amorphous thin strip

A method for producing a soft magnetic thin ribbon, comprising the steps of:

• casting an alloy melt into a shape of an amorphous thin ribbon having a thickness of not greater than 100 μm, the alloy having a composition represented by a formula:
• Fe100-x-y-zAxMyXz-aPa, where A represents at least one element selected from Cu and Au;
• M represents at least one element selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W;
• X represents B and Si;
• and 0.7≦x≦1.3, 0≦y≦2.5, 10≦z≦23, and 2≦a≦10 in atomic percent,
• the alloy including crystalline grains having a size of not greater than 30 nm precipitated in a volume fraction of not more than 1%, including 0%, in an amorphous phase, and the amorphous thin ribbon being able to be bent at 180 degrees;
• working the amorphous thin ribbon with a cutting tool;
• and
• then annealing the amorphous thin ribbon at an average heating rate of not less than 100° C./min in a temperature range from 300° C. to an annealing temperature, the annealing temperature being higher than a crystallization temperature, to obtain a soft magnetic thin ribbon having a structure where crystalline grains having a grain size of not greater than 60 nm (excluding 0) are dispersed at a volume fraction of not less than 30% in an amorphous phase.