An object of the present invention is to provide a magnetic recording medium capable of suppressing a dimensional change in a width direction by setting the water vapor transmission rate within a specific range.

The present technology provides a magnetic recording medium having a tape shape, the magnetic recording medium including: a magnetic layer; a nonmagnetic layer; a base layer; and a back layer in this order, in which the magnetic layer and the nonmagnetic layer are in contact with each other, the nonmagnetic layer and the base layer are in contact with each other, an average thickness of the magnetic recording medium is 5.74 μm or less, a Young's modulus in an MD direction (longitudinal direction) of the base layer is 5.9 GPa or less, and a water vapor transmission rate of the magnetic recording medium, measured according to a Lyssy method, is 2.93 g/m.sup.2.Math.day or less. The Young's modulus in the MD direction of the base layer (longitudinal direction) is 5.3 GPa or less. A humidity expansion coefficient β at a temperature of 10° C. is 6.5 ppm/% RH or less.

The magnetic tape cartridge includes a magnetic tape, and a cartridge reel, in which, in the magnetic tape, a minimum winding deviation occurrence load measured after the magnetic tape is rewound around the cartridge reel by applying a tension of 0.20 N in a longitudinal direction of the magnetic tape is 200 N or less.

The magnetic tape includes a non-magnetic support; and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support, in which an absolute value ΔN of a difference between a refractive index Nxy measured regarding an in-plane direction of the magnetic layer and a refractive index Nz measured regarding a thickness direction of the magnetic layer is 0.25 to 0.40, and a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding a surface of the magnetic layer is equal to or smaller than 0.050.

A magnetic recording medium is a magnetic recording medium having a tape shape and includes a substrate, an underlayer provided on the substrate, and a magnetic layer provided on the underlayer. The magnetic layer has a surface having an uneven shape, a height range ΔH obtained from statistical information of a height of the uneven shape is in a range of 4.00 nm≤ΔH≤10.00 nm, and a gradient range ΔA obtained from statistical information of a gradient of the uneven shape is in a range of 2.50 degrees≤ΔA.

The magnetic tape includes: a non-magnetic support; and a magnetic layer containing a ferromagnetic powder, in which a non-linear component of a signal phase difference generated by storage for 10 days in an environment of a temperature of 60° C. and a relative humidity of 20% is 17.5 nm or less. A magnetic tape cartridge and a magnetic tape apparatus include the magnetic tape.

It is an object of the present technology to provide a magnetic recording medium that has a small total thickness and achieves excellent travelling stability. The present technology provides a tape-shaped magnetic recording medium including a magnetic layer, an underlayer, a base layer, and a back layer, in which a servo pattern is recorded in the magnetic layer, a statistical value σ.sub.SW indicating non-linearity of a servo band and being obtained from a reproduction waveform of a servo signal of the servo pattern is 24 nm or less, the base layer contains polyester as a main component, an average thickness t.sub.T of the magnetic recording medium is 5.6 μm or less, the magnetic recording medium contains a lubricant, pores are formed in the magnetic recording medium, and an average diameter of the pores of the magnetic recording medium that is measured in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried, is 6 nm or more and 11 nm or less.

A magnetic recording medium is a tape-shaped magnetic recording medium, including: a substrate; an underlayer provided on the substrate; and a magnetic layer provided on the underlayer. The substrate contains polyester, each of the underlayer and the magnetic layer contains a lubricant, the magnetic layer has a surface on which a large number of holes is provided, the arithmetic average roughness Ra of the surface is 2.5 nm or less, a BET specific surface area of the entire magnetic recording medium measured in a state where the magnetic recording medium has been washed and dried is 3.5 m.sup.2/g or more and 7.0 m.sup.2/g or less, a squareness ratio of the magnetic layer in a vertical direction is 65% or more, an average thickness of the magnetic layer is 80 nm or less, an average thickness of the magnetic recording medium is 5.6 .Math.m or less, and a servo pattern is recorded on the magnetic layer and a statistical value σsw indicating a non-linearity of the servo pattern is 24 nm or less.

A cobalt ferrite magnetic powder includes magnetic particles that have a uniaxial crystal magnetic anisotropy and contain cobalt ferrite. A peak top 2θ of a (3, 1, 1) plane determined by powder X-ray diffractometry using a CoKα ray is 41.3° or more and 41.5° or less. Some Cos contained in the magnetic particles are substituted with at least one selected from the group consisting of Zn, Ge, and a transition metal element other than Fe.

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. On the surface of the magnetic layer, recesses having a depth of 20% or more of the average thickness of the magnetic layer are formed at a ratio of 20 or more and 200 or less per 1600 μm.sup.2. On the surface of the magnetic layer, a logarithmic decay rate determined by a pendulum viscoelasticity test at a temperature of 10° C. or higher and 45° C. or lower is 0.025 or more and 0.035 or less. A difference between a maximum value of the logarithmic decay rate and a minimum value of the logarithmic decay rate is 0 or more and 0.020 or less. The squareness ratio in the perpendicular direction is 65% or more. The average thickness of the magnetic layer is 80 nm or less. The average thickness of the magnetic recording medium is 5.6 μm or less.

A tape-like magnetic recording medium includes a reinforced substrate, and a recording layer arranged on the reinforced substrate, and the reinforced substrate includes a substrate that has a first face and a second face opposed to each other, and has an average thickness of 4 μm or smaller, and a metal layer that contains cobalt, arranged on the first face, the reinforced substrate by itself causing thereon a depth of indentation of 0.25 μm or shallower, when a 0.7-mm-diameter hard sphere is impressed against the second face under 5.0 gf load for 10 seconds.