An aspect of the present invention relates to a magnetic recording medium, which comprises magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support, wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, the ferromagnetic hexagonal ferrite powder has an activation volume ranging from 800 nm.sup.3 to 1,300 nm.sup.3, and 1 percent to 50 percent of particles constituting the ferromagnetic hexagonal ferrite powder are ferromagnetic hexagonal ferrite particles, each of which has an indentation with a depth of equal to or more than 1/10 of an equivalent projected circle diameter of the ferromagnetic hexagonal ferrite particle.

Hexagonal ferrite magnetic particles have an activation volume ranging from 1,000 nm.sup.3 to 1,500 nm.sup.3, and ΔE.sub.10%/kT, thermal stability at 10% magnetization reversal, is equal to or greater than 40.

A magnetic recording medium includes: a substrate that is long in shape; and a magnetic layer containing magnetic powder and a binder. The glass transition point of the binder is not lower than 75° C. In a case where atomic force microscope observation images in a 10 μm×10 μm rectangular shape are acquired at five locations randomly selected from the surface on the side of the magnetic layer, any linear protrusion that is 3 nm to 20 nm in height, is 0.3 μm to 1.0 μm in width, and extends across two sides of the observation image does not exist in the observation images of four locations among the acquired observation images of the five locations.

A magnetic recording cartridge is provided and including a magnetic recording medium, wherein an average thickness of the magnetic recording medium t.sub.T is 3.5 μm≤t.sub.T≤5.6 μm, a dimensional change amount Δw in a width direction of the magnetic recording medium with respect to a tension change in a longitudinal direction of the magnetic recording medium is 700 ppm/N≤Δw≤20000 ppm, the magnetic recording medium is accommodated in a state of being wound around the reel in the cartridge case and (a servo track width on an inner side of winding of the magnetic recording medium)−(a servo track width on an outer side of winding of the magnetic recording medium)>0 is satisfied, and a squareness ratio measured in a vertical direction of the magnetic recording medium is 65% or more.

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.after−S.sub.before) between a spacing S.sub.after measured by optical interferometry regarding a surface of the back coating layer after ethanol cleaning and a spacing S.sub.before measured by optical interferometry regarding the surface of the back coating layer before ethanol cleaning is greater than 0 nm and equal to or smaller than 15.0 nm, and the non-magnetic support is an aromatic polyester support having a moisture absorption of 0.3% or less.

A magnetic recording medium is a magnetic recording medium having a tape-like shape and includes a base substrate and a magnetic layer provided on the base substrate. A plurality of data tracks can be formed in the magnetic layer, a width of a data track is 2900 nm or less, and in a case of defining, as w.sub.max and w.sub.min, a maximum value and a minimum value respectively out of average values of a width of the magnetic recording medium measured under four kinds of environment in which temperature and relative humidity are set to (10° C., 10%), (10° C., 80%), (29° C., 80%), and (45° C., 10%), w.sub.max and w.sub.min satisfy a relation of (w.sub.max−w.sub.min)/w.sub.min≤400 [ppm].

The magnetic recording and reproducing device includes a magnetic recording medium, a recording element, and a reproducing element. The recording element is an inductive recording element having a first magnetic pole which generates a magnetic field, and a second magnetic pole which is spaced apart from the first magnetic pole with a write gap interposed therebetween, a tip width of the first magnetic pole is substantially the same as a tip width of the second magnetic pole, and a reproducing element width of the reproducing element is 0.5 μm to 0.8 μm. The magnetic recording medium has a non-magnetic support, and a magnetic layer containing a ferromagnetic powder, and the number of recesses, which are present in a surface of the magnetic layer and have an equivalent circle diameter of 0.20 μm to 0.50 μm, is 10 to 500 per area of 40 μm×40 μm.

A tape-shaped magnetic recording medium includes a substrate; and a magnetic layer that is provided on the substrate and contains a magnetic powder. An average thickness of the magnetic layer is not more than 90 nm, an average aspect ratio of the magnetic powder is not less than 1.0 and not more than 3.0, the coercive force Hc1 in a vertical direction is not more than 3000 Oe, and the coercive force Hc1 in the vertical direction and a coercive force Hc2 in a longitudinal direction satisfy a relationship of Hc2/Hc1≤0.8.

The magnetic recording and reproducing device includes a magnetic recording medium, a recording element, and a reproducing element. The recording element is an inductive recording element having a first magnetic pole which generates a magnetic field, and a second magnetic pole which is spaced apart from the first magnetic pole with a write gap interposed therebetween, a tip width of the first magnetic pole is substantially the same as a tip width of the second magnetic pole, and a reproducing element width of the reproducing element is 0.2 μm or greater and less than 0.5 μm. In the magnetic recording medium, the number of recesses, which are present in a surface of the magnetic layer and have an equivalent circle diameter of 0.10 μm or greater and less than 0.20 μm, is 100 to 2,000 per area of 40 μm×40 μm.

The magnetic tape includes a non-magnetic support; and a magnetic layer in which the magnetic layer has a timing-based servo pattern, an edge shape of the timing-based servo pattern, specified by magnetic force microscopy is a shape in which a difference between a value L.sub.99.9 of a cumulative distribution function of 99.9% and a value L.sub.0.1 of a cumulative distribution function of 0.1% in a position deviation width from an ideal shape of the magnetic tape in a longitudinal direction is 180 nm or less, and a difference between a spacing S.sub.after measured on a surface of the magnetic layer by an optical interferometry after methyl-ethyl-ketone cleaning and a spacing S.sub.before measured on the surface of the magnetic layer by an optical interferometry before methyl-ethyl-ketone cleaning is greater than 0 nm and 15.0 nm or less.