Substrate for magnetic disk

Abstract

The purpose of the present invention is to provide a substrate for a magnetic disk that effectively minimizes the occurrence of head crashes by effectively minimizing undulation present in the outer peripheral area of the disk surface even if it is thin, particularly. The present invention is a substrate for a magnetic disk having a maximum value of arithmetic mean heights Sa of 0.50 nm or less and a standard deviation of the arithmetic mean heights Sa of 0.10 nm or less when the arithmetic mean heights Sa are defined by ISO25178 and are each measured in a plurality of field-of-view areas located on the outer peripheral area of at least one side using scanning optical interferometry in a middle wavelength area through a Gaussian filter with a cutoff wavelength of 1.0 mm.

Dependencies are inferred from the claim text.