A glass-ceramic substrate for a magnetic disk

摘要

A glass-ceramic substrate for a magnetic disk suitable for use as a contact recording type magnetic disk includes alpha-cristobalite (alpha-SiO2) and lithium disilicate (Li2O . 2SiO2) as main crystal phases. The ratio of alpha-cristobalite/lithium disilicate is within a range from 0.25 to 0.35, a grain diameter of crystal grains is within a range from 0.1 mu m to 1.0 mu m, surface roughness (Ra) of the substrate after polishing is within a range from 2 ANGSTROM to 10 ANGSTROM and abrasion resistance index (Aa) of the substrate is within a range from 5 to 15.