A heat-assisted magnetic recording (HAMR) medium includes a substrate, a split heat-sink structure (SHSS) and a magnetic recording layer. The SHSS includes a first heat-sink layer disposed on the substrate, a heat-sink break layer (HSBL) disposed on the first heat-sink layer, and a second heat-sink layer disposed on the HSBL. The magnetic recording layer is disposed on the SHSS. The SHSS is configured to enable use of a reduced operating current of the laser while maintaining about the same write performance properties as a thermal barrier layer, heat-assisted magnetic recording (TBLHAMR) medium that includes a thermal barrier layer (TBL) and a heat-sink layer that is greater than about 20% thicker than the thickness of the SHSS. A HAMR data storage device that incorporates the HAMR medium within a HAMR disk, and a method for making the HAMR medium are also described.

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).

A sputtering target which is made of an alumina sintered body having a purity of not less than 99.99% by mass %, a relative density of not less than 98%, and an average grain size of less than 5 m or is made of an alumina sintered body having a purity of not less than 99.999% by mass % and a relative density of not less than 98%. A sputtered film having an excellent insulation resistance and an excellent homogeneity can be obtained by using the sputtering target.

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).

A recording medium comprising a dielectric magnetic layer, the dielectric magnetic layer comprising anisotropic ions having a difference in a single ion contribution to magnetic anisotropy (?K/ion) between a ground state and an excited state of said anisotropic ions equal to at least 0.1 cm.sup.?1 (0.0124 meV/ion) at 20? C. (68? F.), wherein the effective Gilbert damping (?) of said dielectric magnetic layer is equal to at least 0.01.