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 tape includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder. The non-magnetic support is a polyamide support, and a deformation rate ratio of a deformation rate in a width direction to a deformation rate in a longitudinal direction of the magnetic tape, (the deformation rate in the width direction/the deformation rate in the longitudinal direction), is 0.45 or less, the deformation rates each being measured after a load is applied in the longitudinal direction of the magnetic tape for 96 hours.

The present technology provides a tape-shaped magnetic recording medium including a magnetic layer, an underlayer, a base layer, and a back layer. The magnetic recording medium has an average thickness t.sub.T of 5.4 μm or less, when a thermomechanical analysis is performed on the magnetic recording medium in a temperature range of 40° C. to 150° C. at a temperature rise rate of 1° C./minute, a switching temperature for switching from thermal expansion to thermal contraction is 70° C. or more, and a contraction start temperature is 90° C. or more at which a length in a longitudinal direction is shorter than the length at 40° C., and a Poisson's ratio is 0.40 or less.

The magnetic tape includes a non-magnetic support; and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support, in which the magnetic layer includes one or more components selected from the group consisting of fatty acid and fatty acid amide, a C—H derived C concentration calculated from a C—H peak area ratio of C1s spectra obtained by X-ray photoelectron spectroscopic analysis performed on a surface of the magnetic layer at a photoelectron take-off angle of 10 degrees is equal to or greater than 45 atom %, and an absolute value ΔN of a difference between a refractive index Nxy measured regarding an in-plane direction of the magnetic layer and a refractive index Nz measured regarding a thickness direction of the magnetic layer is 0.25 to 0.40.

The magnetic tape includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder. The non-magnetic support is a polyethylene naphthalate support, and a deformation rate ratio of a deformation rate in a width direction to a deformation rate in a longitudinal direction of the magnetic tape, (the deformation rate in the width direction/the deformation rate in the longitudinal direction), is 0.42 or less, the deformation rates each being measured after a load is applied in the longitudinal direction of the magnetic tape for 96 hours.

A magnetic recording medium substrate is provided in which a NiP type plating film is formed on a surface of an aluminum alloy substrate that includes Si in a range of 9.5 mass % or more and 11.0 mass % or less, Mn in a rage of 0.45 mass % or more and 0.90 mass % or less, Zn in a range of 0.32 mass % or more and 0.38 mass % or less, Sr in a range of 0.01 mass % or more and 0.05 mass % or less. In the alloy structure of the aluminum alloy substrate, an average particle diameter of Si particles is 2 μm or less, the film thickness of the NiP type plating film is 7 μm or more. An outer diameter of the magnetic recording medium substrate is 53 mm or more, the thickness is 0.9 mm or less, and the Young's modulus is 79 GPa or more.

Provided are: a magnetic recording medium including a non-magnetic support and a magnetic layer containing a ferromagnetic powder, in which the ferromagnetic powder is an ε-iron oxide powder, a vertical switching field distribution SFD of the magnetic recording medium is 0.20 or more and 3.00 or less at a measurement temperature of 25° C., and an inclination of SFD obtained from SFD at a measurement temperature of 10° C., SFD at a measurement temperature of 25° C., and SFD at a measurement temperature of 40° C. is 0.003° C..sup.-1 or more and 0.080° C..sup.-1 or less; a magnetic tape cartridge including the magnetic recording medium which is a magnetic tape; and a magnetic recording and reproducing device including the magnetic recording medium.

Provided are: a magnetic recording medium including a non-magnetic support and a magnetic layer containing a ferromagnetic powder, in which the ferromagnetic powder is an ε-iron oxide powder, a vertical switching field distribution SFD of the magnetic recording medium is 0.20 or more and 3.00 or less at a measurement temperature of 25° C., and an inclination of SFD obtained from SFD at a measurement temperature of 10° C., SFD at a measurement temperature of 25° C., and SFD at a measurement temperature of 40° C. is 0.003° C..sup.-1 or more and 0.080° C..sup.-1 or less; a magnetic tape cartridge including the magnetic recording medium which is a magnetic tape; and a magnetic recording and reproducing device including the magnetic recording medium.

Provided are: a magnetic recording medium including a non-magnetic support and a magnetic layer containing a ferromagnetic powder, in which the ferromagnetic powder is an ε-iron oxide powder, H.sub.0.2 of the magnetic recording medium is 5,000 Oe or more and 40,000 Oe or less at a measurement temperature of 25° C., and an inclination of H.sub.0.2 obtained from H.sub.0.2 at a measurement temperature of 10° C., H.sub.0.2 at a measurement temperature of 25° C., and H.sub.0.2 at a measurement temperature of 40° C. is −100 Oe/° C. or more and −5 Oe/° C. or less; a magnetic tape cartridge including the magnetic recording medium which is a magnetic tape; and a magnetic recording and reproducing device including the magnetic recording medium.

Provided are: a magnetic recording medium including a non-magnetic support and a magnetic layer containing a ferromagnetic powder, in which the ferromagnetic powder is an ε-iron oxide powder, H.sub.0.2 of the magnetic recording medium is 5,000 Oe or more and 40,000 Oe or less at a measurement temperature of 25° C., and an inclination of H.sub.0.2 obtained from H.sub.0.2 at a measurement temperature of 10° C., H.sub.0.2 at a measurement temperature of 25° C., and H.sub.0.2 at a measurement temperature of 40° C. is −100 Oe/° C. or more and −5 Oe/° C. or less; a magnetic tape cartridge including the magnetic recording medium which is a magnetic tape; and a magnetic recording and reproducing device including the magnetic recording medium.