A data storage device having a housing member for a selected one of a 3 inch form factor hard disc drive (HDD) or a 2 inch form factor HDD. A spindle motor coupled to the housing member supports a rotatable data recording disc with a plurality of data tracks and an outermost perimeter. The outermost perimeter has an average overall radius of 48.5 millimeters, mm responsive to the housing member being for a 3 inch form factor HDD or an average overall radius of 33.5 mm responsive to the housing member being for a 2 inch form factor HDD. The rotatable data recording disc further has an outermost data track at an average selected radius such that the difference between the average overall radius of the outermost perimeter and the average selected radius is more than 1 mm.

A data storage device having a housing member for a selected one of a 3 inch form factor hard disc drive (HDD) or a 2 inch form factor HDD. A spindle motor coupled to the housing member supports a rotatable data recording disc with a plurality of data tracks and an outermost perimeter. The outermost perimeter has an average overall radius of 48.5 millimeters, mm responsive to the housing member being for a 3 inch form factor HDD or an average overall radius of 33.5 mm responsive to the housing member being for a 2 inch form factor HDD. The rotatable data recording disc further has an outermost data track at an average selected radius such that the difference between the average overall radius of the outermost perimeter and the average selected radius is more than 1 mm.

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. The substrate main body at the outer circumferential edge surface forming an interface with the film provided on the outer circumferential edge surface has a surface roughness maximum height Rz of 0.5 m or more.

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.

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.

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.

A glass substrate for a magnetic disk has a disk shape. The glass 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 glass 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. The glass of the glass substrate has a glass transition point of 680 C. or higher.