Disclosed is a perpendicularly magnetized film structure that uses a highly heat resistant underlayer film on which a cubic or tetragonal perpendicularly magnetized film can grow with high quality, the structure comprising any one substrate (5) of a cubic single crystal substrate having a (001) plane, or a substrate having a cubic oriented film that grows to have the (001) plane; an underlayer (6) formed on the substrate (5) from a thin film of a metal having an hcp structure, such as Ru or Re, in which the [0001] direction of the thin metal film forms an angle in the range of 42? to 54? with respect to the <001> direction or the (001) orientation of the substrate (5); and a perpendicularly magnetized layer (7) located on the metal underlayer (6) and formed from a cubic material selected from the group consisting of a Co-based Heusler alloy, a cobalt-iron (CoFe) alloy having a bcc structure, and the like, as a constituent material, and grown to have the (001) plane.

A substrate for a magnetic disk includes a substrate main body and a film. The substrate main body has two opposing main surfaces and an outer circumferential edge surface, and the outer circumferential edge surface includes a side wall surface, which is orthogonal to the main surfaces, and chamfered surfaces, which are disposed between the main surfaces and the side wall surface. The substrate main body is a glass substrate main body or an aluminum alloy substrate main body, and has a disk shape. The film is an alloy film containing Ni and P, and is provided on a surface of the substrate main body such that the film is formed continuously over the main surfaces, the chamfered surfaces, and the side wall surface of the substrate main body.

Apparatus and method for magnetic recording media. A rotatable magnetic recording disc has an outermost annular sidewall that extends at nominally 97 millimeters, mm for a 3- inch form factor data storage device or at nominally 67 mm for a 2- inch form factor data storage device. The rotatable magnetic recording disc further has a disc shaped substrate of metal or glass, and a magnetic recording layer supported by the disc shaped substrate and configured to magnetically record data along concentric tracks.

A substrate for a magnetic disk has a disk shape. The substrate has a diameter D of 85 mm or more and 100 mm or less, and a thickness T of 0.3 mm or more and 0.5 mm or less. Regarding a Young's modulus E and the thickness T of the substrate, a value of E.Math.T.sup.3 is 3 to 18 (GPa.Math.mm.sup.3). A material of the substrate has a Q-value of 1500 or less under conditions of 3000 Hz and room temperature.

Apparatus and method for magnetic recording media. A rotatable magnetic recording disc has an outermost annular sidewall that extends at nominally 97 millimeters, mm for a 3 inch form factor data storage device or at nominally 67 mm for a 2 inch form factor data storage device. The rotatable magnetic recording disc further has a disc shaped substrate of metal or glass, and a magnetic recording layer supported by the disc shaped substrate and configured to magnetically record data along concentric tracks.

A substrate for a magnetic disk includes a substrate main body having two main surfaces and an outer circumferential edge surface, 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 film thicknesses of sections of the film provided on the main surfaces is 0.520 mm or less. A total thickness D mm, which is a sum of the film thicknesses of the sections of the film on the main surfaces and the thickness T mm satisfy D0.0082/T0.0015. A surface roughness maximum height Rz of the film provided on the outer circumferential edge surface is smaller than that of the substrate main body at the outer circumferential edge surface.

The magnetic tape includes a non-magnetic support, and a magnetic layer containing a ferromagnetic powder. A magnetic tape cartridge and a magnetic tape apparatus include the magnetic tape. An arithmetic average curvature Spc of a peak point specified in ISO 25178 on a surface of the magnetic layer is 0.30 (1/m) or more and 0.70 (1/m) or less, and standard deviation a of the Spc in a width direction of the surface of the magnetic layer is 0.15 (1/m) or less.

An enlarged substrate configuration for magnetic recording media. In some embodiments, an apparatus comprises a disc shaped member of metal or glass configured as a substrate for a magnetic data recording disc for a 2 inch form factor data storage device or a 3 inch form factor data storage device. The disc shaped member has a top planar surface, an opposing bottom planar surface, an outermost annular sidewall that extends between the top planar surface and the bottom planar surface at an outermost diameter of nominally 67 or 97 millimeters, respectively, and an inner annular sidewall that extends between the top planar surface and the bottom planar surface to define a central aperture.

An enlarged substrate configuration for magnetic recording media. In some embodiments, an apparatus comprises a disc shaped member of metal or glass configured as a substrate for a magnetic data recording disc for a 2 inch form factor data storage device or a 3 inch form factor data storage device. The disc shaped member has a top planar surface, an opposing bottom planar surface, an outermost annular sidewall that extends between the top planar surface and the bottom planar surface at an outermost diameter of nominally 67 or 97 millimeters, respectively, and an inner annular sidewall that extends between the top planar surface and the bottom planar surface to define a central aperture.

Disclosed is a perpendicularly magnetized film structure that uses a highly heat resistant underlayer film on which a cubic or tetragonal perpendicularly magnetized film can grow with high quality, the structure comprising any one substrate (5) of a cubic single crystal substrate having a (001) plane, or a substrate having a cubic oriented film that grows to have the (001) plane; an underlayer (6) formed on the substrate (5) from a thin film of a metal having an hcp structure, such as Ru or Re, in which the [0001] direction of the thin metal film forms an angle in the range of 42 to 54 with respect to the <001> direction or the (001) orientation of the substrate (5); and a perpendicularly magnetized layer (7) located on the metal underlayer (6) and formed from a cubic material selected from the group consisting of a Co-based Heusler alloy, a cobalt-iron (CoFe) alloy having a bcc structure, and the like, as a constituent material, and grown to have the (001) plane.