| 摘要 |
There is provided a glass-ceramic substrate for a magnetic information storage medium having a data zone and a landing zone capable of stably lifting a magnetic head in the landing zone and also capable of reducing the amount of lifting of the magnetic head in the data zone for realizing a high recording density. The landing zone has a multiplicity of projections or depressions formed by irradiation of laser beam. A CO2 laser or a laser diode pumped solid-state laser can be used for this purpose. The surface roughness (Ra) of a polished surface of the landing zone is within a range from 3 Å to 9 Å, height of the projections or depressions is within a range from 50 Å to 300 Å, surface roughness (Ra) of the projections or depressions is within a range from 10 Å to 50 Å and interval of the projections or depressions is within a range from 10 mum to 200 mum. A preferable glass-ceramic used is a glass-ceramic of a SiO2-Li2O-K2O-MgO-ZnO-P2O5-Al2O3 system or a SiO2-Li2O-K2O-MgO-ZnO-P2O5-Al2O3-ZrO2 system. For stable forming of projections or depressions in the landing zone by a laser diode pumped solid-state laser, the glass-ceramic preferably includes at least two coloring agents selected from NiO, CoO, MnO2, V2O5, CuO and Cr2O3.
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