A disk for a magnetic recording apparatus. The disk includes a substrate comprising a first surface and a second surface, wherein the substrate has a substrate thickness. The disk includes a first coating layer disposed over the first surface of the substrate, wherein the first coating layer has a first coating layer thickness. The disk includes a second coating layer disposed over the second surface of the substrate, wherein the second coating layer has a second coating layer thickness. The disk has a disk thickness, wherein the disk thickness includes the substrate thickness. The maximum thickness difference between the first coating layer thickness and the second coating layer thickness is a function of the square of the disk thickness.

A tape-shaped magnetic recording medium includes a base, a nonmagnetic layer that is provided on the base and contains a nonmagnetic powder, and a magnetic layer that is provided on the nonmagnetic layer and contains a magnetic powder. In the magnetic recording medium, the magnetic layer has an average thickness of not more than 90 nm, the magnetic powder has an average aspect ratio of from 1.0 to 3.0, a coercive force Hc1 in a perpendicular direction is not more than 3,000 Oe, the coercive force Hc1 in the perpendicular direction and a coercive force Hc2 in a longitudinal direction satisfy the relation of Hc2/Hc10.8, the nonmagnetic layer has an average thickness of not more than 1.1 m, and the nonmagnetic powder has an average particle volume of not more than 2.010.sup.5 m.sup.3.

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 NiP 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.

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/Hc10.8.

Provided is an aluminum alloy substrate for a magnetic disk that includes an aluminum alloy containing 0.4 to 3.0 mass % (hereinafter abbreviated as %) of Fe, 0.005% to 1.000% of Cu, and 0.005% to 1.000% of Zn, with a balance of Al and unavoidable impurities. This substrate has a ratio A/B of 0.70 or more, where A indicates a distribution density of AlFe intermetallic compound particles having maximum diameters of 10 m or more and less than 16 m, and B indicates a distribution density of AlFe intermetallic compound particles having maximum diameters of 10 m or more. The distribution density of AlFe intermetallic compound particles having maximum diameters of 40 m or more is at most one per square millimeter. Also provided are a method of fabricating this aluminum alloy substrate for a magnetic disk and a magnetic disk composed of the aluminum alloy substrate for a magnetic disk.

Provided are: an aluminum alloy substrate for a magnetic disk, including an aluminum alloy including 0.4 to 3.0 mass % of Fe with the balance of Al and unavoidable impurities; a method for producing the aluminum alloy substrate for a magnetic disk; and a magnetic disk in which an electroless NiP plating treatment layer and a magnetic layer formed thereon are disposed on a surface of the aluminum alloy substrate for a magnetic disk.

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, the coercive force Hc1 in the vertical direction and a coercive force Hc2 in a longitudinal direction satisfy a relationship of Hc2/Hc10.8, and a value of 1.50.5 is not more than 0.6 N in a tensile test of the magnetic recording medium in the longitudinal direction, where 0.5 is a load at an elongation rate of 0.5% in the magnetic recording medium and 1.5 is a load at an elongation rate of 1.5% in the magnetic recording medium.

There are provided: an aluminum alloy substrate for a magnetic disk, in which the product of the sheet thickness and loss factor of the substrate is 0.710.sup.3 or more; a method for producing the aluminum alloy substrate for a magnetic disk; and a magnetic disk, in which an electroless NiP plating treatment layer and a magnetic layer formed thereon are disposed on a surface of the aluminum alloy substrate for a magnetic disk.

A magnetic recording medium includes a substrate, an underlayer formed on the substrate, and a magnetic layer formed on the underlayer. The magnetic layer includes an alloy having a L1.sub.0 structure. The underlayer includes a first underlayer and a second underlayer. The first underlayer includes Mo and Ru, the content of Ru in the first underlayer is in a range of 5 atom % to 30 atom %, and the second underlayer includes a material having a body-centered cubic (BCC) structure. The second underlayer is formed between the first underlayer and the substrate.

There are provided: an aluminum alloy magnetic disk substrate including: an aluminum alloy base material including an aluminum alloy containing 0.4 to 3.0 mass % (hereinafter, simply referred to as %) of Fe, 0.1 to 3.0% of Mn, 0.005 to 1.000% of Cu, and 0.005 to 1.000% of Zn, with the balance of Al and unavoidable impurities; and an electroless NiP plated layer formed on a surface of the aluminum alloy base material, in which the peak value (BLEI) of Fe emission intensity at an interface between the electroless NiP plated layer and the aluminum alloy base material, as determined by a glow discharge optical emission spectrometry device, is lower than Fe emission intensity (AlEI) in the interior of the aluminum alloy base material, as determined by the glow discharge optical emission spectrometry device; and a method for producing the aluminum alloy magnetic disk substrate.