A method, according to one approach, includes forming an underlayer of a magnetic recording medium. The underlayer includes encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an aromatic polymer, and a polymeric binder binding the encapsulated nanoparticles. A method, according to another approach, includes mixing encapsulated nanoparticles with a polymeric binder and a solvent to form a mixture, the encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an aromatic polymer. The mixture is applied onto a structure. The applied mixture is at least partially dried and cured.

Provided is a magnetic tape cartridge of a single reel type in which a magnetic tape is wound around a reel, in which the magnetic tape includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, a tape thickness is equal to or smaller than 5.2 m, a tape width difference (BA) between a tape width A at a position of 10 m1 m from a tape outer end and a tape width B at a position of 50 m1 m from a tape inner end is 2.4 m to 12.0 m, and the tape width A and the tape width B are values measured 100 days from the date of magnetic tape cartridge manufacture.

An ink-printed substrate includes a substrate and water-based ink composition printed on the substrate, and has a Crockfastness-Loss-to-Density Ratio of about 1.0 to about 6.0.

The magnetic recording medium includes a non-magnetic support, a magnetic layer including a ferromagnetic powder on one surface of the non-magnetic support, and a back coating layer including a non-magnetic powder on the other surface of the non-magnetic support, in which a difference (S.sub.afterS.sub.before) between a spacing S.sub.after measured by optical interferometry regarding a surface of the back coating layer after methyl ethyl ketone cleaning and a spacing S.sub.before measured by optical interferometry regarding the surface of the back coating layer before methyl ethyl ketone cleaning is greater than 0 nm and equal to or smaller than 30.0 nm, and the non-magnetic support is an aromatic polyamide support having a moisture absorption of 2.2% or less.

Provided is a magnetic tape cartridge of a single reel type in which a magnetic tape is wound around a reel, in which the magnetic tape includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, a tape thickness is equal to or smaller than 5.2 m, a tape width difference (BA) between a tape width A at a position of 10 m1 m from a tape outer end and a tape width B at a position of 50 m1 m from a tape inner end is 2.4 m to 12.0 m, and the tape width A and the tape width B are values measured 100 days from the date of magnetic tape cartridge manufacture.

Provided is a magnetic tape cartridge of a single reel type in which a magnetic tape is wound around a reel, in which the magnetic tape includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, a tape thickness is equal to or smaller than 5.2 m, a tape width difference (BA) between a tape width A at a position of 10 m1 m from a tape outer end and a tape width B at a position of 50 m1 m from a tape inner end is 2.4 m to 12.0 m, and the tape width A and the tape width B are values measured 100 days from the date of magnetic tape cartridge manufacture.

A magnetic recording medium includes a substrate, a seed layer, an under layer, and a perpendicular recording layer having a granular structure. (Ms.Math.??.sup.1.5(1?Rs).sup.0.33), Ms, and ? satisfy (Ms.Math.?.Math.?.sup.1.5(1?Rs).sup.0.33)?0.1 [?.Math.emu.Math.(mm).sup.?1.5], Ms?450 [emu/cc], and ??1.2. In the above formulas, Ms indicates a saturated magnetization amount, ? indicates the gradient of a M-H loop around a coercive force Hc, ? indicates the thickness of the perpendicular recording layer, and Rs indicates a squareness ratio.

Provided is a magnetic tape cartridge of a single reel type in which a magnetic tape is wound around a reel, in which the magnetic tape includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, a tape thickness is equal to or smaller than 5.2 a tape width difference (BA) between a tape width A at a position of 10 m1 m from a tape outer end and a tape width B at a position of 50 m1 m from a tape inner end is 2.4 m to 12.0 m, and the tape width A and the tape width B are values measured 100 days from the date of magnetic tape cartridge manufacture.

To provide a resin film, of which dimensional stability required of an ultra-high density recording medium can be controlled easily by drive tension, and which has processability at high temperature in a processing step of the resin film into a magnetic recording medium. A resin film having a Young's modulus in the film longitudinal direction of 1 GPa or more and a film thickness of 1 m or more, wherein the product of the Young's modulus in the longitudinal direction and the thickness is 5 GPa.Math.m or more and 20 GPa.Math.m or less and wherein a dimensional change in the film longitudinal direction is 2% or more and +2% or less when the film is heated at a rate of 5 C./min under a load of 2 kg/mm.sup.2 applied in the longitudinal direction and the temperature has reached 110 C., the resin film satisfying at least either of the following (1) or (2): (1) the Young's modulus in the film longitudinal direction is 6 GPa or less and the film thickness is 4.5 m or less; and (2) the Young's modulus in the film longitudinal direction is 4 GPa or less and the film thickness is 6 m or less.

The magnetic recording medium includes a non-magnetic support; and a magnetic layer containing a ferromagnetic powder, in which a nitrogen-containing polymer is included in a portion on the non-magnetic support on a magnetic layer side, the nitrogen-containing polymer contains a fluorine-containing group and a polyester chain, the fluorine-containing group is bonded to a nitrogen atom of the nitrogen-containing polymer, the polyester chain is bonded to the nitrogen atom of the nitrogen-containing polymer or forms a salt crosslinking structure with the nitrogen atom of the nitrogen-containing polymer, and a contact angle with water, which is measured on a surface of the magnetic layer after hexane cleaning, is 90 or more.