A composite magnetic body includes soft magnetic metal particles and non-magnetic ceramic particles each having a particle size (D50) smaller than that of the soft magnetic metal particles.

A magnetic base body includes plural metal magnetic particles including a first metal magnetic particle and a second metal magnetic particle adjacent to the first metal magnetic particle, each metal magnetic particle including Fe, and plural metal Fe particles including metal Fe. The plural metal Fe particles are disposed separately from each other between an insulating first oxide layer and an insulating second oxide layer. The first oxide layer includes oxide of an element A disposed on a surface of the first metal magnetic particle. The second oxide layer includes oxide of an element B disposed on a surface of the second metal magnetic particle. The element A is at least one element selected from a group consisting of Si, Zr, Al, and Ti, and the element B is at least one element selected from the group consisting of Si, Zr, Al, and Ti.

Mn—Zn ferrite particles according to the present invention contain 44-60% by mass of Fe, 10-16% by mass of Mn and 1-11% by mass of Zn. The ferrite particles are single crystal bodies having an average particle diameter of 1-2,000 nm, and have polyhedral particle shapes, while having an average sphericity of 0.85 or more but less than 0.95.

Mn—Zn ferrite particles according to the present invention contain 44-60% by mass of Fe, 10-16% by mass of Mn and 1-11% by mass of Zn. The ferrite particles are single crystal bodies having an average particle diameter of 1-2,000 nm, and have polyhedral particle shapes, while having an average sphericity of 0.85 or more but less than 0.95.

A method for producing a composite magnetic body includes: pressure molding a metal magnetic material into a predetermined shape, the metal magnetic material being an Fe—Si-based metal magnetic material; performing a primary heat treatment of heating the metal magnetic material in an atmosphere with a first oxygen partial pressure to form an Si oxide coating film on a surface of the metal magnetic material; and performing a secondary heat treatment of heating the metal magnetic material that has undergone the primary heat treatment in an atmosphere with a second oxygen partial pressure, which is higher than the first oxygen partial pressure, to form an Fe oxide layer at least partially on a surface of the Si oxide coating film.

A magnetic particle includes a magnetic metal particle having a plurality of phases. The plurality of phases include an Fe-based phase and an Fe.sub.3O.sub.4 phase. An area ratio of the Fe.sub.3O.sub.4 phase in which the Fe.sub.3O.sub.4 phase occupies in the plurality of phases is less than 50%.

A magnetic particle includes a magnetic metal particle, and an oxide film formed on a surface of the magnetic metal particle, wherein the magnetic metal particle includes a single crystalline zone containing an Fe component, and the oxide film includes an amorphous zone containing an Fe component. The single crystalline zone may include an α-Fe phase.

A compound for dust core includes a metal powder including iron, a resin composition, and a metal salt, in which the metal salt is represented by R.sub.2M, R represents a saturated fatty acid group having 6 or more and 12 or less carbon atoms, and M represents at least one metal element between Ca and Ba.

A compound for dust core includes a metal powder including iron, a resin composition, and a metal salt, in which the metal salt is represented by R.sub.2M, R represents a saturated fatty acid group having 6 or more and 12 or less carbon atoms, and M represents at least one metal element between Ca and Ba.

A composite magnetic material includes a powder and a resin. The powder has a main component containing Fe or Fe and Co. An average minor axis length in primary particles of the powder is 100 nm or less. A point satisfying (X, Y)=(σ/A.sub.v (%), (A.sub.v-σ)) on an XY coordinate plane is present within a region (including a boundary) surrounded by three points α(24.5, 6.7), β(72.0, 1.2), and γ(24.5, 1.2), in which an average of aspect ratios in the primary particles of the powder is set to A.sub.v, and a standard deviation of the aspect ratios in the primary particles of the powder is set to σ.