A magnetic tape in which a minimum value of TDStens among five TDStens measured respectively at a temperature of 16° C. and a relative humidity of 20%, a temperature of 16° C. and a relative humidity of 80%, a temperature of 26° C. and a relative humidity of 80%, a temperature of 32° C. and a relative humidity of 20% and a temperature of 32° C. and a relative humidity of 55% is 1.43 μm/N or more, a ratio of a change of TDStens to a change of a relative humidity obtained from the five TDStens is 0.005 μm/N/% or less, and a ratio of a change of TDStens to a change of a temperature obtained from the five TDStens is 0.020 μm/N/° C. or less.

The magnetic tape includes a magnetic layer having ferromagnetic powder and a binder on a non-magnetic support, in which the magnetic layer includes a timing-based servo pattern, the ferromagnetic powder is ferromagnetic hexagonal ferrite powder having an activation volume equal to or smaller than 1,600 nm.sup.3, and an edge shape of the timing-based servo pattern specified by a magnetic force microscope observation is a shape in which a difference (l.sub.99.9−l.sub.0.1) between a value l.sub.99.9 of a cumulative frequency function of 99.9% of a position deviation width from an ideal shape in a longitudinal direction of the magnetic tape and a value l.sub.0.1 of the cumulative frequency function of 0.1% thereof is equal to or smaller than 180 nm.

The magnetic recording medium includes: a non-magnetic support; and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, in which the magnetic layer further includes a compound including a polyalkyleneimine chain and a vinyl polymer chain. The composition for a magnetic recording medium includes: ferromagnetic powder; and a compound including a polyalkyleneimine chain and a vinyl polymer chain.

The magnetic recording medium contains, in a magnetic layer, a fatty acid ester and a polyester resin having a number average molecular weight of greater than or equal to 1,000 but less than 20,000, and containing a structural unit derived from a polyvalent carboxylic acid and a structural unit derived from a polyol, as well as 10 mol % to 50 mol % of a structural unit, derived from a cyclic polyvalent carboxylic acid selected from the group consisting of an alicyclic polyvalent carboxylic acid and an aromatic polyvalent carboxylic acid, per 100 mol % of a combined total of the above structural units, and one or more partial structures selected from the group consisting of the following partial structures:

##STR00001##

wherein each of L.sup.1 and L.sup.2 independently denotes a divalent connecting group, and each of Z.sup.1 and Z.sup.2 independently denotes a monovalent group denoted by —OM or a monovalent group denoted by —O.sup.−A.sup.+.

The magnetic tape has a magnetic layer containing ferromagnetic powder and binder on one surface of a nonmagnetic support and has a backcoat layer containing nonmagnetic powder and binder on the other surface thereof, wherein the thickness of the backcoat layer is less than or equal to 0.20 μm, the contact angle for 1-bromonaphthalene that is measured on the surface of the backcoat layer falls within a range of 10.0° to 30.0°, and the contact angle for 1-bromonaphthalene that is measured on the surface of the magnetic layer falls within a range of 45.0° to 55.0°.

An aspect of the present invention relates to a magnetic recording medium, which comprises a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support, wherein the magnetic layer further comprises a compound which has a weight average molecular weight of equal to or more than 1,000 but less than 20,000 and is denoted by formula (1): ##STR00001##
wherein, in formula (1), A.sup.1 denotes a monovalent polymer group, each of R.sup.1 and R.sup.2 independently denotes a single bond or a divalent connecting group, R.sup.11 denotes a hydrogen atom or a monovalent substituent, m denotes an integer of equal to or greater than 2, multiple instances of R.sup.1, R.sup.2, A.sup.1, and R.sup.11 that are present can be identical or different, A.sup.2 denotes a hydrogen atom or a monovalent substituent denoted by —OR.sup.3—Z, R.sup.3 denotes a single bond or a divalent connecting group, Z denotes a monovalent acid group, among multiple instances of A.sup.2 that are present, at least one denotes a monovalent group denoted by —O—R.sup.3—Z, and X denotes a connecting group of valence m.

A magnetic recording tape, in accordance with one aspect of the present invention, includes a substrate, an underlayer formed above the substrate, and a magnetic recording layer formed above the underlayer. The underlayer includes first encapsulated nanoparticles each comprising a first magnetic nanoparticle encapsulated by a first aromatic polymer, and a first polymeric binder binding the first encapsulated nanoparticles. The recording layer includes second encapsulated nanoparticles each comprising a second magnetic nanoparticle encapsulated by an encapsulating layer, and a second polymeric binder binding the second encapsulated nanoparticles.

The magnetic recording medium includes: a non-magnetic support; and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, in which the magnetic layer further includes a compound including a polyalkyleneimine chain and a vinyl polymer chain. The composition for a magnetic recording medium includes: ferromagnetic powder; and a compound including a polyalkyleneimine chain and a vinyl polymer chain.

A magnetic recording tape, in accordance with one aspect of the present invention, includes a substrate, an underlayer formed above the substrate, and a magnetic recording layer formed above the underlayer. The underlayer includes first encapsulated nanoparticles each comprising a first magnetic nanoparticle encapsulated by a first aromatic polymer, and a first polymeric binder binding the first encapsulated nanoparticles. The recording layer includes second encapsulated nanoparticles each comprising a second magnetic nanoparticle encapsulated by an encapsulating layer, and a second polymeric binder binding the second encapsulated nanoparticles.

The magnetic recording medium includes a non-magnetic support; and a magnetic layer including a ferromagnetic powder, in which an isoelectric point of a surface zeta potential of the magnetic layer after pressing the magnetic layer at a pressure of 70 atm is equal to or greater than 5.5.