An object of the present disclosure is to provide a magnetic recording medium excellent in electro-magnetic conversion characteristic and thermal stability.

The present disclosure provides a tape-shaped magnetic recording medium including: a substrate; and a magnetic layer provided over the substrate and including a magnetic powder, in which the magnetic layer has an average thickness of equal to or less than 90 nm, the magnetic powder has an average aspect ratio of from 1.0 to 3.0, the magnetic powder has an average particle volume of equal to or less than 2,300 nm.sup.3, a coercive force Hc1 in a vertical direction of the magnetic recording medium is equal to or less than 4,500 Oe, a coercive force Hc2 in a longitudinal direction of the magnetic recording medium and the coercive force Hc1 satisfy a relation of Hc2/Hc1≤0.8, and the ratio Hrp/Hc1 of a residual coercive force Hrp of the magnetic recording medium measured using a pulsed magnetic field and the coercive force Hc1 is equal to or less than 2.0.

The magnetic tape cartridge includes a magnetic tape that is accommodated in the magnetic tape cartridge while being wound around a reel hub. A water absorption amount of the magnetic tape measured after the magnetic tape cartridge is stored in a storage environment of a temperature of 32° C. and a relative humidity of 80% for 10 days is more than 0.30 g as a value in terms of a length of the magnetic tape of 1000 m, and the water absorption amount is a value measured in a measurement environment with a temperature of 21° C. and a relative humidity of 50% within 1 hour after the storage.

The magnetic tape cartridge includes a magnetic tape that is accommodated in the magnetic tape cartridge while being wound around a reel hub. A water absorption amount of the magnetic tape measured after the magnetic tape cartridge is stored in a storage environment of a temperature of 32° C. and a relative humidity of 80% for 10 days is 0.30 g or less as a value in terms of a length of the magnetic tape of 1000 m, and the water absorption amount is a value measured in a measurement environment with a temperature of 21° C. and a relative humidity of 50% within 1 hour after the storage.

A glass disk for a magnetic recording medium of the present invention has a disk shape, and has a strain point of 695° C. to 780° C., a temperature at 10.sup.4.5 dPa.Math.s of 1300° C. or lower, and a Young's modulus of 78 GPa or higher.

A glass disk for a magnetic recording medium of the present invention has a disk shape, and has a strain point of 695° C. to 780° C., a temperature at 10.sup.4.5 dPa.Math.s of 1300° C. or lower, and a Young's modulus of 78 GPa or higher.

An aluminum alloy substrate for magnetic disks, including an aluminum alloy containing Fe as an essential element; at least one of Mn or Ni as selective elements; and the balance including Al and unavoidable impurities, with the total amount of Fe, Mn, and Ni having a relationship of 0.10 to 7.00 mass %; 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.

An aluminum alloy substrate for magnetic disks, including an aluminum alloy containing Fe as an essential element; at least one of Mn or Ni as selective elements; and the balance including Al and unavoidable impurities, with the total amount of Fe, Mn, and Ni having a relationship of 0.10 to 7.00 mass %; 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.

Disks for use in hard disk drives (HDD) or other magnetic recording apparatus. The disks are configured based on a finding that internal stress within a disk can make the disk more resistant to shock forces. In one example, a disk is provided that has a substrate with a thickness of no more than 0.5 millimeters and an internal stress no less than 300 megapascals. The relatively high internal stress within the substrate of the disk serves to reduce the magnitude of deflections caused by mechanical shocks to an HDD in which the disk is installed, as compared to other disks of equal thickness but with relatively less internal stress. Multi-platter stacks of the disks are described. Methods are also described for fabricating such disks and for rejecting disks that do not meet certain internal stress-based criteria. Substrates are also described.

An object of the present disclosure is to provide a magnetic recording medium excellent in electro-magnetic conversion characteristic and thermal stability. The present disclosure provides a tape-shaped magnetic recording medium including: a substrate; and a magnetic layer provided over the substrate and including a magnetic powder, in which the magnetic layer has an average thickness of equal to or less than 90 nm, the magnetic powder has an average aspect ratio of from 1.0 to 3.0, the magnetic powder has an average particle volume of equal to or less than 2,300 nm.sup.3, a coercive force Hc1 in a vertical direction of the magnetic recording medium is equal to or less than 4,500 Oe, a coercive force Hc2 in a longitudinal direction of the magnetic recording medium and the coercive force Hc1 satisfy a relation of Hc2/Hc1≤0.8, and the ratio Hrp/Hc1 of a residual coercive force Hrp of the magnetic recording medium measured using a pulsed magnetic field and the coercive force Hc1 is equal to or less than 2.0.

An ionic liquid comprising: a cation (or conjugate acid), wherein the cation (or conjugate acid) is represented by General Formula (A) below or General Formula (B) below or General Formula (C) or General Formula (D) below or General Formula (E) below: ##STR00001## wherein R.sub.1 represents CH.sub.2CH.sub.2(CF.sub.2).sub.nCF.sub.3, where n is an integer ranging from 0 to 7, or an alkyl chain CH.sub.3, or CH.sub.2OH, or CH.sub.2CH.sub.2OH; R.sub.2 represents CH.sub.2CH.sub.2(CF.sub.2).sub.nCF.sub.3, where n is an integer ranging from 0 to 7, or a hydrogen atom H, or CH.sub.2OH, or CH.sub.2CH.sub.2OH; and R.sub.3 represents CH.sub.2CH.sub.2(CF.sub.2).sub.nCF.sub.3, where n is an integer ranging from 0 to 7.