Glass-ceramic substrate for a magnetic information recording medium

Abstract

A glass-ceramic substrate for a magnetic information recording medium contains, as a main crystal phase or phases, one or more crystal phases selected from the group consisting of β-quartz (β-SiO2), β-quartz solid solution (β-SiO2 solid solution), β-spodumene (β-Li2O.Al2O3.4SiO2), β-spodumene solid solution (β-Li2O.Al2O3.4SiO2 solid solution), β-eucryptite (β-Li2O.Al2O3.2SiO2, a part of Li2O being capable of being substituted by MgO and/or ZnO) and β-eucryptite solid solution (β-Li2O.Al2O3.2SiO2 solid solution, a part of Li2O being capable of being substituted by MgO and/or ZnO). Alternatively, the glass-ceramic contains, as a main crystal phase or phases, gahnite (ZnAl2O4) and/or gahnite solid solution (ZnAl2O4 solid solution). The glass-ceramic substrate has a high heat resisting property and a super flat surface capable of achieving a high recording density according to the perpendicular magnetic recording.

Dependencies are inferred from the claim text.