Metal magnetic particle, inductor, method for manufacturing metal magnetic particle, and method for manufacturing metal magnetic core

1. A metal magnetic core comprising:

metal magnetic particles, each metal magnetic particle comprising an oxide layer formed on a surface of an alloy particle containing Fe and Si, the oxide layer including a first oxide layer, a second oxide layer, and a third oxide layer from a side of the alloy particle, and all of the first oxide layer, the second oxide layer, and the third oxide layer containing Si, and

wherein

the metal magnetic particles are joined to each other by the oxide layer to form the metal magnetic core,

in line analysis of element content by using a scanning transmission electron microscope-energy dispersive X-ray spectroscopy,

the first oxide layer is a layer having Fe content smaller than Si content in the alloy particle,

the second oxide layer is a layer having Fe content larger than the Si content in the alloy particle, and

the third oxide layer is a layer having Fe content smaller than the Si content in the alloy particle.

2. The metal magnetic core according to claim 1 , wherein

a weight percentage of Si in the alloy particles is from 1.5 parts by weight to 8.0 parts by weight with respect to 100 parts by weight of a total weight of the Fe and the Si.

3. The metal magnetic core according to claim 1 , wherein

the alloy particles contain smaller than 1.0 part by weight of Cr with respect to 100 parts by weight of a total weight of the Fe and the Si.

4. An inductor comprising:

the metal magnetic core according to claim 1 .

5. The metal magnetic core according to claim 2 , wherein

the alloy particles contain smaller than 1.0 part by weight of Cr with respect to 100 parts by weight of a total weight of the Fe and the Si.

6. An inductor comprising:

the metal magnetic core according to claim 2 .

7. An inductor comprising:

the metal magnetic core according to claim 3 .

8. A method for manufacturing the metal magnetic core of claim 1 , the method comprising:

mixing raw material particles each of which has, on a surface of an alloy particle containing Fe and Si, an Si oxide film and an Fe oxide film from a side of the alloy particle with Si alkoxide and alcohol;

forming coating film forming particles each of which is formed with a coating film containing silicon oxide, by hydrolyzing and drying the Si alkoxide;

molding the coating film forming particles; and

forming an oxide layer on a surface of each of the alloy particles by performing heat treatment on a molded body of the coating film forming particles in an oxidizing atmosphere, wherein

an average thickness of the coating film is from larger than 14 nm to 30 nm, and

a temperature of the heat treatment is from 600° C. to lower than 750° C.

9. The method for manufacturing the metal magnetic core according to claim 8 , wherein

the molding includes laminating and pressing a green sheet containing the coating film forming particles.

10. The method for manufacturing the metal magnetic core according to claim 8 , wherein

the Si alkoxide is tetraethoxysilane.

11. The method for manufacturing the metal magnetic core according to claim 9 , wherein

the Si alkoxide is tetraethoxysilane.

12. The metal magnetic core according to claim 1 , wherein

the second oxide layer has a larger maximum content of Si than the third oxide layer.

13. The metal magnetic core according to claim 1 , wherein

the third oxide layer contains Fe.

14. The metal magnetic core according to claim 13 , wherein

a ratio of the Fe content to the Si content at the point where the Si content of the third oxide layer takes the local maximum value is equal to or larger than about 0.1 and equal to or smaller than about 0.5.