Coating-type magnetic recording medium for heat-assisted recording, and heat-assisted magnetic recording apparatus and heat-assisted magnetic recording method using the same
The magnetic recording medium disclosed in the present application includes a non-magnetic support, an undercoat layer, a magnetic layer containing magnetic particles, and a back coat layer. The coercive force Hc of the magnetic layer in the thickness direction at 25° C. is not 4100 oersteds (Oe) or more, and the coercive force Hc of the magnetic layer in the thickness direction at a temperature between 55° C. and 80° C. inclusive is not less than 1200 oersteds (Oe) and not more than 3700 oersteds (Oe).
1. A coating-type magnetic recording medium for heat-assisted recording, comprising:
a non-magnetic support; and
a magnetic layer containing magnetic particles,
wherein a coercive force Hc of the magnetic layer in a thickness direction at 25° C. is 4100 oersteds (Oe) or more,
the coercive force Hc of the magnetic layer in the thickness direction at a temperature between 55° C. and 80° C. inclusive is not less than 1200 oersteds (Oe) and not more than 3700 oersteds (Oe),
the magnetic particles comprise ε-iron oxide represented by a general composition formula ε-M x Fe 2-x O 3 ,
in the general composition formula ε-M x Fe 2-x O 3 , M represents one or more elements other than Fe, and
in the general composition formula ε-M x Fe 2-x O 3 , in a case where a molar ratio between M and Fe is represented by x/(2−x), the following relationships (1) to (3) are satisfied:
(1) 0.4≤x/(2−x)≤0.9 is satisfied in a case where M represents a single element of Ga;
(2) 0.1≤x/(2−x)≤0.18 is satisfied in a case where M represents three elements of Ti, Co, and Al; and
(3) 0.1≤x/(2−x)≤0.30 is satisfied in a case where M represents three elements of Ti, Co, and Ga.
2. The coating-type magnetic recording medium according to claim 1 , wherein
the coercive force Hc of the magnetic layer in the thickness direction at 25° C. is 4500 oersteds (Oe) or more, and the coercive force Hc of the magnetic layer in the thickness direction at a temperature between 60° C. and 70° C. inclusive is not less than 1900 oersteds (Oe) and not more than 3500 oersteds (Oe).
3. The coating-type magnetic recording medium according to claim 1 , wherein
the coercive force Hc of the magnetic layer in the thickness direction at 25° C. is 10,000 oersteds (Oe) or less.
4. The coating-type magnetic recording medium according to claim 1 , wherein
a temperature dependence of the coercive force Hc of the magnetic layer in the thickness direction is −30 oersteds (Oe)/° C. or less.
5. The coating-type magnetic recording medium according to claim 1 , further comprising an undercoat layer between the non-magnetic support and the magnetic layer,
wherein the undercoat layer is in direct contact with the magnetic layer.
6. The coating-type magnetic recording medium according to claim 1 , wherein
recording and reproduction are performed at a surface recording density of 15 Gb/in 2 or more.
7. The coating-type magnetic recording medium according to claim 1 , having an overall thickness of 5.0 μm or less.
8. A heat-assisted magnetic recording apparatus comprising:
the coating-type magnetic recording medium according to claim 1 ; and
a magnetic recording head for heat-assisted recording.
9. A heat-assisted magnetic recording method comprising:
performing heat-assisted recording by heating the coating-type magnetic recording medium according to claim 1 .
10. The heat-assisted magnetic recording method according to claim 9 , wherein
a recording portion of the magnetic layer in the coating-type magnetic recording medium is heated to a temperature between 55° C. and 80° C. inclusive.
11. The heat-assisted magnetic recording method according to claim 9 , wherein
a recording portion of the magnetic layer in the coating-type magnetic recording medium is heated to a temperature between 60° C. and 70° C. inclusive.