Patent ID: 8241516

Claim:
A method for manufacturing a substrate for a magnetic disk, comprising the steps of: (a) polishing a substrate with a polishing composition A comprising: alumina abrasives having an average particle size of from 0.1 to 0.4 μm, wherein the alumina abrasives comprise an α-alumina and an intermediate alumina; an oxidizing agent, wherein the oxidizing agent is hydrogen peroxide in an amount of 0.01% to 5% by weight; and an acid, wherein the acid is one or more members selected from the group consisting of inorganic acids and polycarboxylic acids, wherein the acid is in an amount of 0.01% to 5% by weight; and wherein a pH of composition A is from 0.1 to 3; and (b) polishing the substrate with a polishing composition B comprising silica particles having an average particle size of from 0.005 to 0.1 μm, wherein the substrate obtained after step (a) has surface properties of a long-wavelength waviness of 0.05 nm or more and 0.25 nm or less.