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.

A substrate for a magnetic disk includes a substrate main body having two main surfaces and an outer circumferential edge surface that has a side wall surface and chamfered surfaces, and a film that is an alloy film containing Ni and P and provided on a surface of the substrate main body. A disk shape of the substrate main body has an outer diameter of 90 mm or more. A thickness T of the substrate that includes the film provided on the main surfaces is 0.520 mm or less. A total thickness D mm of the film on the main surfaces and the thickness T mm satisfy D≥0.0082/T−0.0015. A film thickness of the film on the outer circumferential edge surface is larger than a film thickness of the film on the main surfaces, and is 150% or less of the film thickness of the film on the main surfaces.

An object of the present disclosure is to provide a magnetic recording medium excellent in electro-magnetic conversion characteristic and thermal stability.

The present disclosure provides a tape-shaped magnetic recording medium including: a substrate; and a magnetic layer provided over the substrate and including a magnetic powder, in which the magnetic layer has an average thickness of equal to or less than 90 nm, the magnetic powder has an average aspect ratio of from 1.0 to 3.0, the magnetic powder has an average particle volume of equal to or less than 2,300 nm.sup.3, a coercive force Hc1 in a vertical direction of the magnetic recording medium is equal to or less than 4,500 Oe, a coercive force Hc2 in a longitudinal direction of the magnetic recording medium and the coercive force Hc1 satisfy a relation of Hc2/Hc1≤0.8, and the ratio Hrp/Hc1 of a residual coercive force Hrp of the magnetic recording medium measured using a pulsed magnetic field and the coercive force Hc1 is equal to or less than 2.0.

An object of the present disclosure is to provide a magnetic recording medium excellent in electro-magnetic conversion characteristic and thermal stability. The present disclosure provides a tape-shaped magnetic recording medium including: a substrate; and a magnetic layer provided over the substrate and including a magnetic powder, in which the magnetic layer has an average thickness of equal to or less than 90 nm, the magnetic powder has an average aspect ratio of from 1.0 to 3.0, the magnetic powder has an average particle volume of equal to or less than 2,300 nm.sup.3, a coercive force Hc1 in a vertical direction of the magnetic recording medium is equal to or less than 4,500 Oe, a coercive force Hc2 in a longitudinal direction of the magnetic recording medium and the coercive force Hc1 satisfy a relation of Hc2/Hc1≤0.8, and the ratio Hrp/Hc1 of a residual coercive force Hrp of the magnetic recording medium measured using a pulsed magnetic field and the coercive force Hc1 is equal to or less than 2.0.

A disk-shaped substrate for a magnetic disk has a diameter D of 85 mm or more and a thickness T of 0.6 mm or less, and a material of the substrate has a Young's modulus E of 90 GPa or more.

A fluorine-containing ether compound represented by R.sup.1—R.sup.2—CH.sub.2—R.sup.3—CH.sub.2—R.sup.4—R.sup.5 is provided. (R.sup.3 is a perfluoropolyether chain; R.sup.1 and R.sup.5 are each independently any one of an alkyl group that may have a substituent, an organic group having at least one double bond or at least one triple bond, and a hydrogen atom; and —R.sup.2—CH.sub.2—R.sup.3 is represented by Formula (2), and R.sup.3—CH.sub.2—R.sup.4— is represented by Formula (3))
-[A]-[B]—O—CH.sub.2—R.sup.3  (2)
R.sup.3—CH.sub.2—O—[C]-[D]-  (3)
([A] is represented by Formula (4), [B] is represented by Formula (5), [C] is represented by Formula (6), [D] is represented by Formula (7), and in the formula, a and b are integers of 0 to 2, c is an integer of 2 to 5, d and f are integers of 0 to 2, and e is an integer of 2 to 5, and at least one of b and d in the formula is 1 or more) ##STR00001##

A stacked-thin-film structure that includes an Llo-ordered MnAl layer having high perpendicular magnetic anisotropy (PMA). In some embodiments, the Ll0-ordered MnAl layer has an Mn content in a range of about 35% to about 65%, a thickness less than about 50 nm, a saturation magnetization of about 100 emu/cm3 to about 600 emu/cm3 and a magnetocrystalline anisotropy of at least 1×106 erg/cm. In some embodiments, the high-PMA Llo-ordered MnAl material is incorporated in magnetic tunneling junction stacked-film structures that are part of magnetoelectronic circuitry, such as spin-transfer-torque magnetoresistive random access memory circuitry and magnetic logic circuitry. In some embodiments, the high-PMA Llo-ordered MnAl material is incorporated into other devices, such as into read/write heads and/or recording media of hard-disk-drive devices.

According to the present invention, there is provided a recording medium comprising a substrate, a platinum layer formed on the substrate and having a (111) plane preferentially oriented, and a fullerene single crystal thin film formed on the platinum layer, and configured to be a recording layer, wherein an average value of average surface roughness Ra's with respect to four or more visual fields measured by using an atomic force microscope in a surface of the fullerene thin film is 0.5 nm or less.

A substrate for a magnetic disk includes a substrate main body having two main surfaces and an outer circumferential edge surface that has a side wall surface and chamfered surfaces, and a film that is an alloy film containing Ni and P and provided on a surface of the substrate main body. A disk shape of the substrate main body has an outer diameter of 90 mm or more. A thickness T of the substrate that includes the film provided on the main surfaces is 0.520 mm or less. A total thickness D mm of the film on the main surfaces and the thickness T mm satisfy D≥0.0082/T−0.0015. A film thickness of the film on the outer circumferential edge surface is larger than a film thickness of the film on the main surfaces, and is 150% or less of the film thickness of the film on the main surfaces.

A magnetic recording medium that can exhibit good traveling performance during use is provided. This magnetic recording medium is a tape-shaped magnetic recording medium, and includes a substrate including a polyester as a main component, a base layer disposed on the substrate, a magnetic layer disposed on the base layer, and a back layer disposed on a side of the substrate opposite to the base layer. A surface of the back layer opposite to the substrate has a kurtosis of 2.0 or more. On a surface of the magnetic layer, recesses having a depth of 20% or more of the average thickness of the magnetic layer are formed at a ratio of 10 or more and 200 or less per 1600 μm.sup.2. A surface of the magnetic layer has arithmetic average roughness Ra of 2.5 nm or less. The entire magnetic recording medium has a BET specific surface area of 3.5 m.sup.2/g or more in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried.