A magnetic recording medium is a magnetic recording medium in the form of a tape and includes a substrate, a foundation layer provided on the substrate, and a magnetic layer provided on the foundation layer and containing a magnetic powder. The foundation layer and the magnetic layer each contain a lubricant. A squareness ratio of the magnetic layer in a perpendicular direction is equal to or higher than 65%, an average thickness of the magnetic recording medium is equal to or smaller than 5.6 μm, a plurality of recessed portions each having a depth corresponding to 20% or higher of the average thickness of the magnetic layer is provided on a surface of the magnetic layer, and the number of the recessed portions per unit area of 1,600 μm.sup.2 of the surface of the magnetic layer is equal to or greater than 20 and equal to or smaller than 200, and an amount of exudation of the lubricant per unit region of 12.5 μm×9.3 μm on the surface of the magnetic layer in a vacuum is equal to or greater than 3.0 μm.sup.2 and equal to or smaller than 6.5 μm.sup.2.

The present invention provides a glass composition having a low density and having a specific elastic modulus high enough to reduce deflection. The glass composition includes, as components, in mol %: 60 to 75% SiO.sub.2; 5 to 15% Al.sub.2O.sub.3; 0.5 to 5% MgO; 0.5 to 10% CaO; 5 to 20% Li.sub.2O; 2 to 10% Na.sub.2O; and 0 to 5% K.sub.2O, and has a density of 2.48 g/cm.sup.3 or less. The glass composition has a specific elastic modulus of, for example, 33.5×10.sup.6 Nm/kg or more.

An aluminum alloy substrate for a magnetic disk including an aluminum alloy containing 0.1 to 3.0 mass % of Fe, 0.005 to 1.000 mass % of Cu, and 0.005 to 1.000 mass % of Zn, with a balance of Al and inevitable impurities, wherein in an outer peripheral surface thereof, the number of holes having maximum diameters of 10 μm or more is 200/mm.sup.2 or less, an aluminum alloy base disk for a magnetic disk and a magnetic disk, using the aluminum alloy substrate, and methods for manufacturing these.

Various embodiments of the present disclosure provide a read/write device for a hard-disk memory system. The read/write device includes a fixed structure; a membrane region including a first and a second membrane, which are constrained to the fixed structure, and a central portion, interposed between the first and second membranes; a first and a second piezoelectric actuator, mechanically coupled, respectively, to the first and second membranes; and a read/write head, which is fixed to the central portion of the membrane region. The first and second piezoelectric actuators can be controlled so as to cause corresponding deformations of the first and second membranes, said deformations of the first and second membranes causing corresponding movements of the read/write head with respect to the fixed structure.

Various apparatuses, systems, methods, and media are disclosed to provide a magnetic recording medium that capping layer doped with an effective amount of metal to control grain-to-grain exchange coupling in a capping layer. A magnetic recording medium includes a substrate, a magnetic recording layer (MRL) on the substrate, and a capping layer on the MRL. The capping layer include Co and is doped with a metal (e.g., Ru or Ta) in a range from 1 atomic percent to 5 atomic percent, inclusive.

The area of a spacer that is to be provided between the adjacent substrates in a laminate including a plurality of substrates to keep the adjacent substrates apart from each other is smaller than those of the stacked substrates. When pressure is released to bring the laminate obtained by providing the spacers between the substrates from a pressed state in which 0.60 MPa of pressure is applied to the laminate in the stacking direction into a non-pressed state, an amount of change ΔW in thickness per spacer that is calculated from a change in the thickness of the laminate due to the release of pressure is 30 μm or less.

A substrate for a magnetic disk includes a substrate main body having a disk shape and an alloy film. The substrate has a thickness (T+D) of 0.520 mm or less, which is the sum of a thickness T of the substrate main body and a thickness D of the film formed on main surfaces of the substrate main body. The disk shape has an outer diameter of 90 mm or more. A ratio D/T of the thickness D to the thickness T is 0.025 or more. The thickness of the film formed on an outer circumferential edge surface of the substrate main body is greater than the thickness of the film formed on each of the main surfaces, and the thickness of the film formed on each of the main surfaces is 80% or more of the thickness of the film formed on the outer circumferential edge surface.

A magnetic recording medium that can exhibit good traveling performance during use is provided. This magnetic recording medium is a tape-shaped magnetic recording medium, and includes a substrate, a base layer disposed on the substrate, and a magnetic layer disposed on the base layer. The substrate includes a polyester as a main component. The average thickness of the base layer is 0.9 μm or less. The base layer and the magnetic layer each include a lubricant. The magnetic layer has a surface having a large number of holes, and the arithmetic average roughness Ra of the surface is 2.5 nm or less. The BET specific surface area of the entire magnetic recording medium is 3.5 m.sup.2/g or more in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried. The squareness ratio in the perpendicular direction is 65% or more. The average thickness of the magnetic layer is 90 nm or less. The average thickness of the magnetic recording medium is 5.6 μm or less.

An aluminum alloy substrate for magnetic disks, including an aluminum alloy containing: 1.0 to 6.5 mass % of Mg; and the balance consisting of Al and unavoidable impurities, in which the distribution of Si—K—O-based particles with a longest diameter of 1 μm or more adhering to the surface from the surrounding environment is equal to or less than one particle/6,000 mm.sup.2; and in which the distribution of Ti—B-based particles with a longest diameter of 1 μm or more present on the surface is equal to or less than one particle/6,000 mm.sup.2, and a magnetic disk using the aluminum alloy substrate for magnetic disks.

An aluminum alloy substrate for magnetic disks, including an aluminum alloy containing: 1.0 to 6.5 mass % of Mg; and the balance consisting of Al and unavoidable impurities, in which the distribution of Si—K—O-based particles with a longest diameter of 1 μm or more adhering to the surface from the surrounding environment is equal to or less than one particle/6,000 mm.sup.2; and in which the distribution of Ti—B-based particles with a longest diameter of 1 μm or more present on the surface is equal to or less than one particle/6,000 mm.sup.2, and a magnetic disk using the aluminum alloy substrate for magnetic disks.