The magnetic tape cartridge includes a magnetic tape, and a cartridge reel. 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 0.40 N in a longitudinal direction of the magnetic tape is 300 N or less.

A magnetic recording medium for microwave-assisted recording, including a non-magnetic support; and a magnetic layer containing a ferromagnetic powder and a binding agent, in which the ferromagnetic powder has an average particle size of 5 nm to 20 nm, and a coefficient of variation of a particle size distribution of 35% or lower, and the magnetic layer has a thickness of 25.0 nm to 100.0 nm, and a thickness variation of 1.0 nm to 12.0 nm. A magnetic recording device including a magnetic recording medium and a magnetic head for microwave-assisted recording. A manufacturing method of a magnetic recording medium having a servo pattern on a magnetic layer.

A hexagonal strontium ferrite powder, in which an average particle size is 10.0 to 25.0 nm, a content of one or more kinds of atom selected from the group consisting of a gallium atom, a scandium atom, an indium atom, and an antimony atom is 1.0 to 15.0 atom % with respect to 100.0 atom % of an iron atom, and a coercivity Hc is greater than 2,000 Oe and smaller than 4,000 Oe. A magnetic recording medium including: a non-magnetic support; and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, in which the ferromagnetic powder is the hexagonal strontium ferrite powder. A magnetic recording and reproducing apparatus including this magnetic recording medium.

A magnetic recording medium used on a record/playback device with a minimum recording wavelength or 50 nm or shorter, the magnetic recording medium including a magnetic layer that contains a spinel-type ferrite magnetic powder, the magnetic layer having an average thickness of 85 nm or smaller, and the magnetic layer having a saturation flux density of 1600 Gauss or larger and 2000 Gauss or smaller.

The magnetic recording medium includes a non-magnetic support; a non-magnetic layer which contains a non-magnetic powder and is provided on the non-magnetic support; and a magnetic layer which contains a ferromagnetic powder and is provided on the non-magnetic layer, in which a thickness of the non-magnetic layer is less than 0.7 μm, and an average 5-point peak height Rpm is 30 nm or lower and the number of projections having a height of 5 nm or higher is 5,000 or more, as obtained by using an atomic force microscope in a measurement region of 90 μm square on a surface of the magnetic layer.

A method of producing a magnetic powder includes performing heat treatment on first particles that contain ferrous oxide to prepare 5 second particles that contain ε-iron oxide.

Provided is a magnetic recording medium capable of suppressing deterioration of running stability even after repeated recording or reproduction is performed.

The magnetic recording medium is a magnetic recording medium having a tape shape, and includes a substrate, an underlayer provided on one surface of the substrate and including a magnetic powder and a binder, and a magnetic layer provided on the underlayer and including a nonmagnetic powder and a binder. The magnetic recording medium has an average thickness of 5.3 μm or less. In a case where a correlation between an amount of projected particles and an erosion depth is obtained in each of the underlayer and the magnetic layer by a micro slurry-jet erosion (MSE), a calculation of a ratio of a particle amount required to wear an erosion depth range to the erosion depth range is performed in each of the underlayer and the magnetic layer on the basis of the correlation, and a result of the calculation is defined as an MSE resistance value of each of the underlayer and the magnetic layer, the ratio of the MSE resistance value of the magnetic layer to the MSE resistance value of the underlayer is in a range of 0.45 or more and 0.80 or less.

The magnetic recording medium includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder. A magnetic tape cartridge and a magnetic recording and reproducing device include the magnetic recording medium. The ferromagnetic powder is an ε-iron oxide powder, and a ferromagnetic powder filling rate of a magnetic layer cross section obtained by observing a cross section of the magnetic layer with a scanning electron microscope is 0.60 or more and 0.80 or less.

The magnetic recording medium includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder. A magnetic tape cartridge and a magnetic recording and reproducing device include the magnetic recording medium. The ferromagnetic powder is an ε-iron oxide powder, and a ferromagnetic powder filling rate of a magnetic layer surface obtained by observing a surface of the magnetic layer with a scanning electron microscope is 0.40 or more and 0.60 or less.

A magnetic recording medium is provided and includes a layer structure including a magnetic layer, a non-magnetic layer, and a base layer in order, in which an average thickness t.sub.T of the magnetic recording medium is 4.0 μm≤t.sub.T≤5.3 μm, a dimensional variation Δw in a width direction of the magnetic recording medium to tension change in a longitudinal direction of the magnetic recording medium is 680 ppm/N≤Δw≤2000 ppm/N, and an average thickness t.sub.n of the non-magnetic layer is t.sub.n≤1.0 μm.