Provided are a magnetic disk and a method of fabricating the magnetic disk. The magnetic disk includes an aluminum alloy plate fabricated by a process involving a CC method and a compound removal process, and an electroless Ni—P plating layer disposed on the surface of the plate. The aluminum alloy plate is composed of an aluminum alloy containing 0.4 to 3.0 mass % (hereinafter abbreviated simply as “%”) of Fe, 0.1% to 3.0% of Mn, 0.005% to 1.000% of Cu, 0.005% to 1.000% of Zn, with a balance of Al and unavoidable impurities. In the magnetic disk, the maximum amplitude of waviness in a wavelength range of 0.4 to 5.0 mm is 5 nm or less, and the maximum amplitude of waviness in a wavelength range of 0.08 to 0.45 mm is 1.5 nm or less.

Provided are a thin hard disk substrate that is scratch-resistant on the disk surface and wobbles less during rotation and a hard disk device including such a hard disk substrate. The hard disk substrate 1 includes an aluminum alloy substrate 2 having NiP plating films 3 on the surfaces. The aluminum alloy substrate 2 has the Vickers hardness of 60 Hv or more, the ratio between the thickness of the NiP plating films 3 and the thickness of the Al alloy substrate 2 is 3.8% or more, the Young's modulus of the hard disk substrate 1 is 74.6 GPa or more, and the Vickers hardness of the hard disk substrate 1 is 293 Hv or more.

A tape-shaped magnetic recording medium includes a substrate; and a magnetic layer that is provided on the substrate and contains a magnetic powder. An average thickness of the magnetic layer is not more than 90 nm, an average aspect ratio of the magnetic powder is not less than 1.0 and not more than 3.0, the coercive force Hc1 in a vertical direction is not more than 3000 Oe, and the coercive force Hc1 in the vertical direction and a coercive force Hc2 in a longitudinal direction satisfy a relationship of Hc2/Hc1≤0.8.

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.

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 sheet for a magnetic disk, a method for manufacturing same, and a magnetic disk using same. The aluminum alloy sheet is made of an aluminum alloy comprising 0.10 to 3.00 mass % of Fe, 0.003 to 1.000 mass % of Cu, and 0.005 to 1.000 mass % of Zn, with a balance of Al and unavoidable impurities, wherein a value obtained by dividing a difference in an area ratio (%) of second phase particles between a region (A) and a region (B) by an average value of area ratios (%) of second phase particles in the regions (A) and (B) is 0.05 or less, the region (A) being a region from a sheet thickness center plane to a front surface of the sheet, and the region (B) being a region from the sheet thickness center plane to a rear surface of the plate.

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 heat-assisted magnetic recording (HAMR) medium has a multilayered underlayer between the heat-sink layer and the recording layer. One embodiment of the underlayer is a multilayer of a thermal barrier layer consisting essentially of MgO and TiO, and a seed layer containing MgO and nitrogen (N) directly on the thermal barrier layer, with the recording layer on and in contact with the seed layer. The interface between the thermal barrier layer and the seed layer contains Ti and N, some of which may be present as TiN to act as a diffusion barrier to prevent diffusion of the Ti into the recording layer. The Ti-containing thermal barrier layer has a higher thermal resistivity than the conventional MgO thermal barrier/seed layer and thus allows for reduced laser power to the recording layer while still achieving a high thermal gradient at the recording layer.

A substrate for a magnetic disk has a disk shape. The substrate has a diameter D of 85 mm or more and a thickness T of 0.6 mm or less. When an impact is applied to the substrate under conditions of 70 (G) and 2 (msec) in a normal direction of main surfaces of the substrate in a state in which an inner circumferential end portion of the substrate is fixed, the maximum amplitude of vibration in a thickness direction of an outer circumferential end portion of the substrate is 0.25 mm or less, the substrate is a non-magnetic metal substrate, and regarding the Young's modulus E and the thickness T of the substrate, a value of E.Math.T.sup.3 is 3 to 18 (GPa.Math.mm.sup.3).

There are provided: an aluminum alloy substrate for a magnetic disk, the aluminum alloy substrate including an aluminum alloy including 0.4 to 3.0 mass % of Fe and the balance of Al and unavoidable impurities, in which second phase particles having a longest diameter of 0.5 μm or more and less than 2.0 μm are dispersed at a distribution density of 5000 particles/mm.sup.2 or more; a method for producing the same; and a magnetic disk using the aluminum alloy substrate for a magnetic disk.