Glass for magnetic recording medium substrate, magnetic recording medium substrate, magnetic recording medium, glass spacer for magnetic recording and reproducing apparatus, and magnetic recording and reproducing apparatus
Provided is a glass for a magnetic recording medium substrate, which is an amorphous glass, in which an SiO 2 content is in a range of 54 mol % or more and 62 mol % or less, an MgO content is in a range of 15 mol % or more and 28 mol % or less, an Li 2 O content is in a range of 0.2 mol % or more, and an Na 2 O content is in a range of 5 mol % or less.
1. A glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording and reproducing apparatus, which is an amorphous glass,
wherein an SiO 2 content is in a range of 54 mol % or more and 62 mol % or less,
an MgO content is in a range of 15 mol % or more and 28 mol % or less,
an Li 2 O content is in a range of 0.2 mol % or more,
an Na 2 O content is in a range of 5 mol % or less,
a mole ratio of the total content of SiO 2 and MgO relative to the Li 2 O content [(SiO 2 +MgO)/Li 2 O] is 13 or more, as well as
wherein a mole ratio of the total content of Al 2 O 3 and CaO relative to the MgO content [(Al 2 O 3 +CaO)/MgO] is 0.80 or more, and/or
a mole ratio of the MgO content relative to a CaO content (MgO/CaO) is 8 or more.
2. The glass according to claim 1 ,
wherein the total content of SiO 2 , MgO, Li 2 O, Al 2 O 3 , and CaO (SiO 2 +MgO+Li 2 O+Al 2 O 3 +CaO) is 93 mol % or more.
3. A magnetic recording medium substrate comprising the glass according to claim 1 .
4. A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 3 ; and a magnetic recording layer.
5. A magnetic recording and reproducing apparatus comprising the magnetic recording medium according to claim 4 .
6. A magnetic recording medium substrate comprising the glass according to claim 2 .
7. A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 6 ; and a magnetic recording layer.
8. A magnetic recording and reproducing apparatus comprising the magnetic recording medium according to claim 7 .
9. A glass spacer for a magnetic recording and reproducing apparatus, comprising the glass according to claim 1 .
10. A glass spacer for a magnetic recording and reproducing apparatus, comprising the glass according to claim 2 .
11. A magnetic recording and reproducing apparatus comprising the glass spacer according to claim 9 .
12. A magnetic recording and reproducing apparatus comprising the glass spacer according to claim 10 .