The magnetic tape device includes: a magnetic tape; and a reproducing head, in which a magnetic tape transportation speed of the magnetic tape device is equal to or lower than 18 m/sec, the reproducing head is a magnetic head including a tunnel magnetoresistance effect type element as a reproducing element, the magnetic tape includes a non-magnetic support, and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support, the magnetic layer includes one or more components selected from the group consisting of fatty acid and fatty acid amide, and a CH derived C concentration calculated from a CH peak area ratio of C1s spectra obtained by X-ray photoelectron spectroscopic analysis performed on the surface of the magnetic layer at a photoelectron take-off angle of 10 degrees is 45 to 65 atom %.

The magnetic tape device includes: a magnetic tape; and a reproducing head, in which a magnetic tape transportation speed of the magnetic tape device is equal to or lower than 18 m/sec, the reproducing head is a magnetic head including a tunnel magnetoresistance effect type element as a reproducing element, the magnetic tape includes a non-magnetic support, and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support, the magnetic layer includes one or more components selected from the group consisting of fatty acid and fatty acid amide, and a CH derived C concentration calculated from a CH peak area ratio of C1s spectra obtained by X-ray photoelectron spectroscopic analysis performed on the surface of the magnetic layer at a photoelectron take-off angle of 10 degrees is 45 to 65 atom %.

An object of the present invention is to provide a magnetic powder having a narrow particle size distribution of epsilon-type iron oxide particles, and another object is to provide magnetic powder suitable for magnetic recording medium by improving particle size distribution, and provide epsilon-type iron oxide magnetic particles and related technologies in which a number average particle diameter of major diameters (D.sub.50) is 10 to 20 nm, a 90% cumulative particle diameter (D.sub.90) is 30 nm or less, and a geometric standard deviation (.sub.g) of major diameters is 1.45 or less, which are obtained by TEM observation.

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

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

A method, according to one approach, includes forming an underlayer of a magnetic recording medium. 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. A magnetic recording layer is formed above the underlayer. The magnetic 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.

A method, according to one approach, includes forming an underlayer of a magnetic recording medium. 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. A magnetic recording layer is formed above the underlayer. The magnetic 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.

A fractionation method for magnetic recording-magnetic powder includes: applying a magnetic field to a liquid that contains magnetic recording-magnetic powder dispersed therein; and relatively shifting a position where the magnetic field is applied to the liquid.

A fractionation method for magnetic recording-magnetic powder includes: applying a magnetic field to a liquid that contains magnetic recording-magnetic powder dispersed therein; and relatively shifting a position where the magnetic field is applied to the liquid.

The magnetic tape has a magnetic layer containing ferromagnetic powder and binder on a nonmagnetic support, wherein the centerline average surface roughness Ra as measured on the surface on the magnetic layer side of the magnetic tape is less than or equal to 1.8 nm, and the logarithmic decrement as determined by a pendulum viscoelasticity test on the surface on the magnetic layer side of the magnetic tape is less than or equal to 0.050.