| 简介 |
PROBLEM TO BE SOLVED : To make surely discriminable a magnetic recording medium from other magnetic recording media and prevent an unauthorized action by making a magnetic recording medium include, in a magnetic recording layer, a magnetic material composed of a hard magnetic substance (A), a hard magnetic substance (B) of a smaller coercive force than the hard magnetic substance (A), and a soft magnetic substance (C), and recording fixed information of a plurality of minute bumps and dips arranged in a predetermined direction to the magnetic recording layer. SOLUTION : A plurality of minute bumps and dips 3a are arranged in a scanning direction of a magnetic head to a fixed information area of a magnetic recording layer 3. The magnetic recording layer 3 contains three kinds of magnetic materials. A hard magnetic substance A uses a magnetic material of a coercive force of 6, 000 (e) or larger, e.g. Ba ferrite, Sr ferrite, a rare earth-based material for forming permanent magnets, or the like. A hard magnetic substance B uses a magnetic material having a coercive force in the range of 100-5, 000 (e), for example, magnetic fine particles of γ-Fe2O3, Co-applied γ-Fe2O3, Fe3O4, CrO2 or the like. A soft magnetic substance C uses a magnetic alloy material such as Al, Si, Fe or the like having a coercive force of 200 (e) or smaller. |
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