| 摘要 |
PURPOSE:To improve sufficiently the corrosion resistance of the titled medium by providing a boundary layer having the oxygen atom concn. higher than the mean oxygen atom concn. contained in a ferromagnetic metallic thin film layer in multiple stages on the surface of the uppermost ferromagnetic metallic layer and at the inside. CONSTITUTION:A boundary layer 33 is formed by plasma oxidation, etc. at the interface of ferromagnetic metallic thin film layers which are laminated and formed in >=2 layers and on the surface of the uppermost ferromagnetic thin film layer 34. The oxygen atom concn. in the boundary layer 33 is preferably regulated to a value 5% higher than the mean oxygen atom concn. contained in the ferromagnetic metallic thin film layers 32 and 34. When the concn. is lower than the value, the corrosion resistance of the ferromagnetic metallic thin film layers 32 and 34 is not sufficiently improved. Besides, the thickness of the boundary layer 33 thus formed is preferably regulated to 20-100Angstrom , the corrosion resistance is not sufficiently improve at <20Angstrom , and the metallic thin film layers 32 and 34 become brittle and the durability is deteriorated at >100Angstrom .
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