Powder for dust cores, method for producing same, dust core and method for producing dust core

A method for producing a powder for dust cores, comprising:

• preparing a raw material powder that includes an aggregate of soft magnetic metal particles;
• forming many ferrite fine particles on a surface of each of the soft magnetic metal particles of the raw material powder by a spray method;
• and
• coarsely crystallizing the ferrite fine particles through heat treatment to form a ferrite film, which includes ferrite crystal grains having a spinel structure, on the surface of the each of the soft magnetic metal particles,
• wherein the heat treatment comprises heating the ferrite fine particles to a temperature in a range of 400 to 900° C.

A dust core comprising:

• a soft magnetic metal particle;
• and
• a ferrite film that covers a surface of the soft magnetic metal particle and includes ferrite crystal grains having a spinel structure,
• wherein
• a diffraction peak derived from the ferrite crystal grains exists in a powder X-ray diffraction pattern,
• the ferrite film includes a part where an interface between the ferrite crystal grains has a straight-line shape in a sectional view of the ferrite film, and
• strain of the dust core has been removed.