Fe-based soft magnetic alloy and dust core using fe-based soft magnetic alloy

An Fe-based soft magnetic alloy consisting of:

• Fe;
• and
• a component R,
• wherein the component R is at least one element selected from the group consisting of P, C, B, and Si,
• there is a temperature difference of equal to or greater than 20° C. between a precipitation temperature of an α-Fe crystal phase and a precipitation temperature of an Fe compound,
• the Fe-based soft magnetic alloy is formed of a mixed-phase structure in which an amorphous phase and the α-Fe crystal phase are mixed,
• a diameter of a crystallite of the α-Fe crystal phase is equal to or smaller than 50 nm, and a volume fraction of the α-Fe crystal phase to a total is equal to or smaller than 40%,
• a composition formula is represented by Fe100−x−uJxRu,
• a component J is at least one element selected from the group consisting of Cr, Co, Ni, and Nb, and
• x and u representing composition ratios satisfy:
• 0 at %≦x≦6 at %, 17 at %≦u≦25 at %, and 17 at %≦x+u≦27.1 at %.