Patent ID: 7901802
Filing Date: 2011-03-08
Classification: G11B

Abstract:
1. A magnetic recording medium for perpendicular magnetic recording, said recording medium comprising: a substrate; a soft underlayer structure disposed over said substrate, an intermediate layer disposed over said underlayer structure; and a perpendicular magnetic recording layer disposed over said intermediate layer, and wherein said soft underlayer structure comprises five soft magnetic layers μ 1 to μ 5 , with soft magnetic layer μ 5 nearest the substrate having the highest magnetic permeability, soft magnetic layer μ 1 nearest the recording layer having the lowest magnetic permeability, and soft magnetic layers μ 4 , μ 3 and μ 2 having magnetic permeabilities less than the magnetic permeability of the soft magnetic layer μ 5 and greater than the magnetic permeability of the soft magnetic layer μ 1 , wherein the soft magnetic layers are each separated by a non-magnetic spacer layer comprising a material selected from Ru and Ta, wherein a permeability (μ) of the soft magnetic layers is selected to form a gradient that increases across the depth of the soft underlayer structure from a soft underlayer nearest the recording layer to a soft underlayer nearest the substrate, and wherein: soft magnetic layer μ soft magnetic layers μ soft magnetic layers μ