Magnetic recording medium
A magnetic recording medium comprising a non-magnetic support and a magnetic layer containing a hexagonal ferrite and a binder, which is for recording a signal having a recording wavelength of from 0.1 to 0.3 μm, wherein a magnetization reversal volume is from 3×10 −18 to 10×10 −18 mL, and after DC magnetization in a perpendicular direction and storage for 24 hours under a circumference at 60° C., a demagnetization factor in perpendicular magnetization expressed by the following formula is not more than 3%: (Demagnetization factor in perpendicular magnetization (%)]=100×{[Residual magnetic flux density ( Br ) after storage]/[Residual magnetic flux density ( Br ) before storage]}
1 . A magnetic recording medium comprising a non-magnetic support and a magnetic layer containing a hexagonal ferrite and a binder, which is for recording a signal having a recording wavelength of from 0.1 to 0.3 μm, wherein a magnetization reversal volume is from 3×10 −18 to 10×10 −18 mL, and after DC magnetization in a perpendicular direction and storage for 24 hours under a circumference at 60° C., a demagnetization factor in perpendicular magnetization expressed by the following formula is not more than 3%:
[Demagnetization factor in perpendicular magnetization (%)]=100×{[Residual magnetic flux density ( Br ) after storage]/[Residual magnetic flux density ( Br ) before storage]}.
2 . The magnetic recording medium according to claim 1 , further comprising a non-magnetic layer containing a non-magnetic powder and a binder between the non-magnetic support and the magnetic layer.
3 . The magnetic recording medium according to claim 2 , wherein the non-magnetic layer further contains carbon black.
4 . The magnetic recording medium according to claim 1 , wherein the magnetic layer further contains carbon black.
5 . The magnetic recording medium according to claim 1 , wherein the magnetization reversal volume is from 3.0×10 −18 to 9.0×10 −18 mL.
6 . The magnetic recording medium according to claim 1 , wherein the demagnetization factor in perpendicular magnetization is not more than 1%.
7 . The magnetic recording medium according to claim 1 , wherein the hexagonal ferrite has a primary particle volume of from 1.7×10 −18 to 14×10 −18 mL.
8 . The magnetic recording medium according to claim 1 , wherein the hexagonal ferrite has a primary particle volume of from 2.5×10 −18 to 9.0×10 −18 mL.
9 . The magnetic recording medium according to claim 1 , wherein the hexagonal ferrite has a mean particle size of from 15 to 40 nm.
10 . The magnetic recording medium according to claim 1 , wherein the hexagonal ferrite has a mean particle size of from 20 to 35 nm.
11 . The magnetic recording medium according to claim 1 , wherein the hexagonal ferrite has a tabular ratio of from 2.0 to 5.0.
12 . The magnetic recording medium according to claim 1 , wherein the hexagonal ferrite has a tabular ratio of from 2.5 to 4.5.
13 . The magnetic recording medium according to claim 1 , further comprising an undercoat layer containing a polyester resin between the non-magnetic support and the magnetic layer.
14 . The magnetic recording medium according to claim 13 , wherein the undercoat layer has a thickness of from 0.01 to 0.8 μm.
15 . The magnetic recording medium according to claim 13 , wherein the undercoat layer has a thickness of from 0.02 to 0.6 μm.