The magnetic recording medium includes a support and a magnetic layer containing a magnetic powder. The magnetic powder includes at least either of a magnetic particle containing a cubic ferrite and a magnetic particle containing an -phase iron oxide. The magnetic powder has a mean particle size of 10 nm or more and 14 nm or less, the magnetic powder has a mean aspect ratio of 0.75 or more and 1.25 or less, and the magnetic layer has a ten-point mean roughness Rz of 35 nm or less.

A heat-assisted magnetic recording (HAMR) disk has a magnetic recording layer (typically a FePt chemically-ordered alloy), a seed-thermal barrier layer (typically MgO) below the recording layer, a heat-sink layer, and an optical-coupling multilayer of alternating plasmonic and non-plasmonic materials between the heat-sink layer and the seed-thermal barrier layer. Unlike a heat sink layer, the multilayer has very low in-plane and out-of-plane thermal conductivity and thus does not function as a heat sink layer. The multilayer's low thermal conductivity allows the multilayer to also function as a thermal barrier. Due to the plasmonic materials in the multilayer it provides excellent optical coupling with the near-field transducer (NFT) of the HAMR disk drive.

The magnetic recording medium includes a non-magnetic support; and a magnetic layer including a ferromagnetic powder, in which the ferromagnetic powder is an -iron oxide powder having an average particle size of 5.0 nm to 16.0 nm, a coercivity Hc in a vertical direction is 1,884 Oe to 3,141 Oe, a ten-point average roughness Rz of a surface of the magnetic layer is 35.0 nm to 45.0 nm, and a ratio Rp/Rz of a maximum peak height Rp of the surface of the magnetic layer to the Rz is 0.25 to 1.00.

An apparatus includes a first magnetic layer. A second magnetic layer overlies the first magnetic layer and is magnetically softer than the first magnetic layer. An exchange control layer is between the first magnetic layer and the second magnetic layer. The includes a higher Ms (saturation magnetization) than the first magnetic layer at room temperature.

This aluminum alloy substrate for a magnetic recording medium has a metal structure made of an Al alloy having a composition including Si in a range of 18.0% by mass to 22.0% by mass, Fe in a range of 4.0% by mass to 6.0% by mass, Cu in a range of 2.5% by mass to 4.0% by mass, and Mg in a range of 0.8% by mass to 1.5% by mass with a remainder being Al, a primary-crystal Si precipitate having a maximum diameter of 0.5 m or more and an average particle diameter of 2 m or less is dispersed in the metal structure, a diameter is in a range of 53 mm to 97 mm, and a thickness is in a range of 0.2 mm to 0.9 mm.

This aluminum alloy substrate for a magnetic recording medium has a metal structure made of an Al alloy having a composition including Si in a range of 18.0% by mass to 22.0% by mass, Ni in a range of 5.0% by mass to 8.5% by mass, Cu in a range of 2.5% by mass to 4.0% by mass, and Mg in a range of 0.8% by mass to 1.5% by mass with a remainder being Al, a primary-crystal Si precipitate having a maximum diameter of 0.5 m or more and an average particle diameter of 2 m or less is dispersed in the metal structure, a diameter is in a range of 53 mm to 97 mm, and a thickness is in a range of 0.2 mm to 0.9 mm.

This substrate for a magnetic recording medium has a metal structure made of an Al alloy having a composition including Si in a range of 28.0% by mass to 32.0% by mass, Cu in a range of 2.5% by mass to 4.0% by mass, and Mg in a range of 0.8% by mass to 1.5% by mass with a remainder being Al, primary-crystal Si particles having a maximum diameter of 0.5 m or more and an average particle diameter of 2 m or less are dispersed in the metallic structure, a diameter of the substrate is in a range of 53 mm to 97 mm, and a thickness of the substrate is in a range of 0.2 mm to 0.9 mm.

An apparatus includes a first magnetic layer. A second magnetic layer overlies the first magnetic layer and is magnetically softer than the first magnetic layer. An exchange control layer is between the first magnetic layer and the second magnetic layer. The includes a higher Ms (saturation magnetization) than the first magnetic layer at room temperature.

An apparatus includes a first magnetic layer. A second magnetic layer overlies the first magnetic layer and is magnetically softer than the first magnetic layer. An exchange control layer is between the first magnetic layer and the second magnetic layer. The exchange control layer is magnetic and increases vertical coupling between the first magnetic layer and the second magnetic layer.

An apparatus includes a first magnetic layer. A second magnetic layer overlies the first magnetic layer and is magnetically softer than the first magnetic layer. An exchange control layer is between the first magnetic layer and the second magnetic layer. The exchange control layer is magnetic and increases vertical coupling between the first magnetic layer and the second magnetic layer.