Magnetic material and coil component using the same

1. A magnetic material constituted by a grain-compacted body comprising:

a plurality of metal grains made of a Fe—Si—M soft magnetic alloy (where M is a metal element more easily oxidized than Fe), and an oxide film formed on the surface of the metal grains;

wherein the oxide film is a film formed by oxidization of the metal grains and bonding the metal grains, which film is constituted by an oxide of the Fe—Si—M soft magnetic alloy of the metal grains, and the mol ratio of the metal element denoted by M relative to the Fe element in the oxide film is greater than the mol ratio of the metal element denoted by M relative to the Fe element in the metal grains; and

wherein there are bonding portions via the oxide film formed on the surface of adjacent metal grains and bonding portions of metal grains bonding together where the oxide film is not present.

2. The magnetic material according to claim 1 , wherein the bonding portions via the oxide film are portions where the oxide film formed on the surface of adjacent metal grains shows the same phase based on a SEM observation image of the oxide film formed on the surface of adjacent metal grains.

3. The magnetic material according to claim 1 , wherein all the Fe—Si—M soft magnetic alloy is a Fe—Cr—Si soft magnetic alloy.

4. The magnetic material according to claim 2 , wherein all the Fe—Si—M soft magnetic alloy is a Fe—Cr—Si soft magnetic alloy.

5. The magnetic material according to claim 1 , wherein a B/N ratio where N represents the number of metal grains in a cross section of the grain-compacted body and B represents the number of bonding portions of metal grains bonding together, is in a range of 0.1 to 0.5.

6. The magnetic material according to claim 2 , wherein a B/N ratio where N represents the number of metal grains in a cross section of the grain-compacted body and B represents the number of bonding portions of metal grains bonding together, is in a range of 0.1 to 0.5.

7. The magnetic material according to claim 1 , wherein the magnetic material is in the form of a compact, the metal grains are constituted by a plurality of metal grains produced by an atomization method, and the oxidization is performed by heat-treating the compact in an oxidizing atmosphere.

8. The magnetic material according to claim 2 , wherein the magnetic material is in the form of a compact, the metal grains are constituted by a plurality of metal grains produced by an atomization method, and the oxidization is performed by heat-treating the compact in an oxidizing atmosphere.

9. The magnetic material according to claim 1 , wherein the grain-compacted body has voids inside and at least some of the voids are impregnated with a polymer resin.

10. The magnetic material according to claim 2 , wherein the grain-compacted body has voids inside and at least some of the voids are impregnated with a polymer resin.

11. A coil component comprising the magnetic material according to claim 1 and a coil formed inside or on a surface of the magnetic material.

12. A coil component comprising the magnetic material according to claim 2 and a coil formed inside or on a surface of the magnetic material.

13. A coil component comprising the magnetic material according to claim 3 and a coil formed inside or on a surface of the magnetic material.

14. A coil component comprising the magnetic material according to claim 5 and a coil formed inside or on a surface of the magnetic material.

15. A coil component comprising the magnetic material according to claim 7 and a coil formed inside or on a surface of the magnetic material.

16. A coil component comprising the magnetic material according to claim 9 and a coil formed inside or on a surface of the magnetic material.

17. The magnetic material according to claim 1 , wherein d50 of the metal grains is in a range of 2 μm to 30 μm.