| 摘要 |
PURPOSE:To form a high electric resistance layer on the surface while improving initial permeability by heating Mn-Zn ferrite, a crystal form thereof recognized through an X-ray diffraction method principally takes magnetite (Fe3O4) and which mainly comprises magnetite and has specific porosity, in an atmosphere containing oxygen. CONSTITUTION:Mn-Zn ferrite 2 consists of 10-20wt% MnO, 10-20wt% ZnO and Fe2O3 as the remainder, and mainly comprises a substance, a crystal form thereof recognized through an X-ray diffraction method principally takes magnetite (Fe3O4), and the remainder is composed of metals or metallic oxides except Mn and Zn. Mn-Zn ferrite employed is of a single crystal or a substance having porosity of less than 5% acquired by sintering powder having a composition of Mn-Zn ferrite through baking through a normal pressure sintering method, a hot pressing method or a hot isotropic pressing method. Such Mn-Zn ferrite 2 is heated in an atmosphere containing oxygen, and high electric resistance layers 1 are formed on the surfaces of ferrite. It is preferable that the partial pressure of oxygen in the heating atmosphere extends over 10<-3> atmospheric pressure or higher. The thickness of the high electric resistance layer 2 extends over 0.5mum or more, and the electric resistance of ferrite having the high electric resistance layer is made higher than ferrite having no high electric resistance layer by 100 times or more. |
