A method for plating nickel onto a glass surface of a substrate by sequentially contacting the surface with a solution having an oxidizing agent, a solution containing a silane compound, a Pd/Sn solution, and a nickel ion-containing solution, thereby accomplishing an electroless nickel plating process.

A magnetic-disk substrate has a pair of main surfaces, and an arithmetic average roughness Ra of each of the main surfaces is 0.11 nm or less. The arithmetic average roughness Ra is a value obtained through measurement using an atomic force microscope provided with a probe having a probe tip provided with a carbon nanofiber rod-shaped member. The magnetic-disk substrate is made of glass or aluminum alloy.

A non-metallic media substrate includes a disc-shaped substrate body having at least one media storage surface on a face thereof. The substrate body has a center opening having an inner diameter and an outer diameter surface, and the substrate body has a thickness. The substrate further includes an annular groove at the outer diameter of the media substrate, the annular groove having chamfered edges and an internal concavity extending toward the inner diameter.

An aluminum alloy sheet for a magnetic disk includes an aluminum alloy comprising 0.10 to 3.00 mass % (hereafter simply “%”) of Fe, 0.1 to 3.0% of Mn, 0.003 to 1.000% of Cu, and 0.005 to 1.000 s % of Zn, wherein second phase particles having a maximum diameter of 100 μm or more and 300 μm or less are dispersed at a distribution density of 50 particles/mm.sup.2 or less in a region (A) occupying 25% or less of a sheet thickness from a sheet thickness center plane to opposite surfaces of the sheet, second phase particles having a maximum diameter of 100 μm or more and 300 μm or less are 0 particles/mm.sup.2 in a region (C) that is obtained by excluding the region (A) from a region (B) occupying 50% or less of the sheet thickness from the sheet thickness center plane to the opposite surfaces of the sheet, and the amount of Mn solid solution is 0.03 mass % or more.

An aluminum alloy substrate (1) for magnetic disk satisfies at least two of three inequalities of an inequality group [A] and satisfies all of four inequalities of an inequality group [B], or satisfies at least two of the three inequalities of the inequality group [A] and satisfies all of four inequalities of an inequality group [C], when a plate thickness of the disk at a position (b1) is defined as t.sub.b1, a plate thickness at a position (b2) is defined as t.sub.b2, a plate thickness at a position (b3) is defined as t.sub.b3, a plate thickness at a position (a1) is defined as t.sub.a1, a plate thickness at a position (a2) is defined as t.sub.a2, and a plate thickness at a position (a3) is defined as t.sub.a3.

A magnetic recording medium according to one embodiment includes an underlayer and a magnetic layer above the underlayer. The magnetic layer includes a first magnetic material and particulates. A solid protective layer is positioned above the magnetic layer, the protective layer including a second material. At least some of the particulates of the magnetic layer protrude completely through the protective layer. A method for forming a magnetic recording medium according to one embodiment includes forming a magnetic layer above a substrate, the magnetic layer including a first magnetic material and particulates, and forming a solid protective layer above the magnetic layer to a thickness whereby some of the particulates protrude through the protective layer and are exposed along an upper surface of the protective layer.

A method for making a magnetic recording tape, in accordance with one approach, includes coupling an underlayer to a substrate, the substrate comprising a poly ether ether ketone (PEEK). A method for making a magnetic recording tape in accordance with another approach includes coupling an underlayer to a substrate via radiation-induced grafting, the substrate comprising a poly ether ether ketone (PEEK). A recording layer is coupled to the underlayer.

Letting a particle diameter be Dx (μm) when a cumulative particle volume cumulated from the small particle diameter side reaches x (%) of the total particle volume in a particle size distribution obtained regarding cerium oxide included in a polishing liquid using a laser diffraction/scattering method, D5 is 1 μm or less, and a difference between D95 and D5 is 3 μm or more.

A sputtering target according to the present invention contains Co and one or more metals selected from the group consisting of Cr and Ru, as metal components, wherein a molar ratio of the content of the one or more metals to the content of Co is ½ or more, and wherein the sputtering target contains Nb.sub.2O.sub.5 as a metal oxide component.

Letting a particle diameter be Dx (μm) when a cumulative particle volume cumulated from the small particle diameter side reaches x (%) of the total particle volume in a particle size distribution obtained regarding cerium oxide included in a polishing liquid using a laser diffraction/scattering method, D5 is 1 μm or less, and a difference between D95 and D5 is 3 μm or more.