In the magnetic tape, a maximum value of magnetic tape deformation amounts after storage in each of five environments for 1 year is 0.50 μm or less, a rate of a change of magnetic tape deformation amount with respect to a change in relative humidity obtained from the five magnetic tape deformation amounts is 0.0001 μm/% to 0.0500 μm/%, and a rate of a change of the magnetic tape deformation amount with respect to a change in temperature obtained from the five magnetic tape deformation amounts is 0.0010 μm/° C. to 0.1000 μm/° C.

The magnetic tape cartridge includes a magnetic tape that is accommodated in the magnetic tape cartridge while being wound around a reel hub. The magnetic tape has a non-magnetic support and a magnetic layer including ferromagnetic powder, and includes one or more components selected from the group consisting of a fatty acid and a fatty acid amide in a portion on the magnetic layer side on the non-magnetic support, and after the magnetic tape cartridge is stored in an environment of an atmosphere temperature of 60° C. and a relative humidity of 80% for 24 hours, a C—H derived C concentration calculated from a C—H peak area ratio of C1s spectra obtained by X-ray photoelectron spectroscopic analysis performed at a photoelectron take-off angle of 10 degrees on a surface of the magnetic layer in an inner region during winding of the magnetic tape is 45 at % or more.

The magnetic recording medium includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder. The ferromagnetic powder is a ferromagnetic powder selected from the group consisting of a hexagonal strontium ferrite powder and an ε-iron oxide powder. The standard deviation of a height of the magnetic projection portion on a surface of the magnetic layer is in a range of 0.5 to 2.5 nm.

An object is to provide a magnetic recording medium having excellent traveling stability and a thin total thickness. 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 surface on a side of the magnetic layer has a kurtosis of 3.0 or more, a surface on a side of the back layer has a kurtosis of 2.0 or more, the surface on the magnetic layer side has arithmetic average roughness R.sub.a of 2.5 nm or less, the base layer includes a polyester as a main component, the magnetic recording medium has an average thickness t.sub.T of 5.6 μm or less, the magnetic recording medium includes a lubricant, the lubricant includes a fatty acid and a fatty acid ester, and a mass ratio between the fatty acid and the fatty acid ester extracted with hexane satisfies fatty acid/fatty acid ester≤0.6, and the magnetic recording medium has pores, and the pores have an average diameter of 6 nm or more and 11 nm or less when the diameters of the pores are measured in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried.

Provided is a ferromagnetic powder for magnetic recording, in which an activation volume is 800 nm.sup.3 to 1,500 nm.sup.3, an average plate ratio is 2.0 to 5.0, a rare earth atom content is 0.5 atom % to 5.0 atom %, and an aluminum atom content is greater than 10.0 atom % and equal to or smaller than 20.0 atom %, with respect to 100 atom % of iron atom, and the ferromagnetic powder is a plate-shaped hexagonal strontium ferrite powder having a rare earth atom surface layer portion uneven distribution and an aluminum atom surface layer portion uneven distribution, and a magnetic recording medium including this ferromagnetic powder for magnetic recording in a magnetic layer.

A magnetic recording medium is a magnetic recording medium in the form of a tape and includes a substrate, a foundation layer provided on the substrate, and a magnetic layer provided on the foundation layer and containing a magnetic powder. The foundation layer and the magnetic layer each contain a lubricant. A squareness ratio of the magnetic layer in a perpendicular direction is equal to or higher than 65%, an average thickness of the magnetic recording medium is equal to or smaller than 5.6 μm, a plurality of recessed portions each having a depth corresponding to 20% or higher of the average thickness of the magnetic layer is provided on a surface of the magnetic layer, and the number of the recessed portions per unit area of 1,600 μm.sup.2 of the surface of the magnetic layer is equal to or greater than 20 and equal to or smaller than 200, and an amount of exudation of the lubricant per unit region of 12.5 μm×9.3 μm on the surface of the magnetic layer in a vacuum is equal to or greater than 3.0 μm.sup.2 and equal to or smaller than 6.5 μm.sup.2.

A hexagonal ferrite magnetic powder is significantly more useful for achieving simultaneously both the enhancement of the recording density and the enhancement of the SNR of a magnetic recording medium. The hexagonal ferrite magnetic powder contains Bi at a Bi/Fe molar ratio in a range of 0.035 or less, has a saturation magnetization σs of 42.0 Am.sup.2/kg or more and a Dx volume calculated based on the crystallite diameters of 1,800 nm.sup.3 or less. A method for producing hexagonal ferrite magnetic powder includes a step of performing a treatment of immersing hexagonal ferrite magnetic powder containing Bi in a solution having dissolved therein a compound X that forms a complex with Bi, so as to elute a part of Bi existing in the hexagonal ferrite magnetic powder into the solution.

The magnetic recording medium has an arithmetic average roughness Ra of a surface of a magnetic layer is 2.2 nm or less, a fluorine concentration A obtained by X-ray photoelectron spectroscopy performed on a surface of the magnetic layer at a photoelectron take-off angle of 10 degrees being 5 atom % or more and 50 atom % or less, and B, which is calculated by Equation 1 from an integrated intensity Ftotal of fragments derived from a fluorine-containing compound obtained for an entire region in a thickness direction of a cross section of the magnetic layer by line profile analysis of TOF-SIMS and an integrated intensity Fupper of fragments derived from a fluorine compound obtained for a region from the surface of the magnetic layer to an intermediate thickness in the thickness direction of the cross section, being 60% or more and 95% or less, Equation 1:B=(Fupper/Ftotal)×100.

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.

A magnetic recording medium includes a substrate, a soft magnetic underlayer on the substrate, and a dual seed layer. The dual seed layer includes a first seed layer comprising NiFe at a first concentration, and a second seed layer comprising NiFe at a second concentration different from the first concentration and a segregant. The first seed layer may be on a soft magnetic underlayer and the second seed layer is on the first seed layer. The magnetic recording medium may further include one or more magnetic recording layers on the dual seed layer. The magnetic recording medium with the composition-graded dual seed layer may provide small grain size and good crystallographic texture for layers on the dual seed layer, including the magnetic recording layers.