Enlarged substrate for magnetic recording medium

An apparatus comprising a rotatable magnetic recording disc for a 2-½ inch form factor data storage device, the rotatable magnetic recording disc comprising an outermost annular sidewall that extends at an outermost diameter of nominally 67 millimeters, mm, 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, the disc shaped substrate having a nominally flat top surface that extends between an innermost diameter toward the outermost annular sidewall to a radius of rolloff (ROR) point at a selected radius, and a relief zone that extends from the ROR point toward the outermost annular sidewall with a continuous change in elevation with respect to the nominally flat top surface, the selected radius of the ROR greater than 31.5 mm from a center of the disc shaped substrate.

An apparatus comprising a magnetic recording disc comprising a disc-shaped substrate on which a magnetic recording layer is formed, the disc-shaped substrate having an outermost annular sidewall at a first radius of nominally 33.5 millimeters, mm or 47.5 mm, a nominally fiat top surface that extends between an innermost diameter toward the outermost annular sidewall to a radius of rolloff (ROR) point at a second radius, and a relief zone that extends from the ROR point toward the outermost annular sidewall with a continuous change in elevation with respect to the nominally flat top surface, the second radius of the ROR point being less than 2 mm from the first radius of the outermost annular sidewall.