Glass for magnetic recording medium substrate, magnetic recording medium substrate and method of manufacturing the same, and magnetic recording medium

摘要

An aspect of the present invention relates to glass for a magnetic recording medium substrate, which comprises, denoted as molar percentages, 50 to 75 percent of SiO2, 0 to 5 percent of Al2O3, 0 to 3 percent of Li2O, 0 to 5 percent of ZnO, a total of Na2O and K2O of 3 to 15 percent, a total of MgO, CaO, SrO, and BaO of 14 to 35 percent, a total of ZrO2, TiO2, La2O3, Y2O3, Yb2O3, Ta2O5, Nb2O5, and HfO2 of 2 to 9 percent, with a molar ratio of {(MgO+CaO)/(MgO+CaO+SrO+BaO)} falling within a range of 0.85 to 1, and a molar ratio of {Al2O3/(MgO+CaO)} falling within a range of 0 to 0.30.