A product, according to one approach, includes a recording layer. The recording layer includes encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an encapsulating layer. A polymeric binder binds the encapsulated nanoparticles. A product, according to another approach, includes a recording layer. The recording layer includes encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an encapsulating layer, and a polymeric binder binding the encapsulated nanoparticles. An average diameter of the magnetic nanoparticles is in a range of 2 nanometers to 20 nanometers. An average thickness of the recording layer is less than 0.2 microns.

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

A fractionation method for magnetic recording-magnetic powder is provided. The method includes applying a magnetic field to a liquid that contains magnetic recording-magnetic powder dispersed therein, wherein the liquid is stored in a storage unit relatively shifting a position where the magnetic field is applied to the liquid; and separating the storage unit into two parts after the shift.

A fractionation method for magnetic recording-magnetic powder is provided. The method includes applying a magnetic field to a liquid that contains magnetic recording-magnetic powder dispersed therein, wherein the liquid is stored in a storage unit relatively shifting a position where the magnetic field is applied to the liquid; and separating the storage unit into two parts after the shift.

A product, according to one approach, includes a recording layer. The recording layer includes encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an encapsulating layer. A polymeric binder binds the encapsulated nanoparticles. A product, according to another approach, includes a recording layer. The recording layer includes encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an encapsulating layer, and a polymeric binder binding the encapsulated nanoparticles. An average diameter of the magnetic nanoparticles is in a range of 2 nanometers to 20 nanometers. An average thickness of the recording layer is less than 0.2 microns.

A product, according to one approach, includes a recording layer. The recording layer includes encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an encapsulating layer. A polymeric binder binds the encapsulated nanoparticles. A product, according to another approach, includes a recording layer. The recording layer includes encapsulated nanoparticles each comprising a magnetic nanoparticle encapsulated by an encapsulating layer, and a polymeric binder binding the encapsulated nanoparticles. An average diameter of the magnetic nanoparticles is in a range of 2 nanometers to 20 nanometers. An average thickness of the recording layer is less than 0.2 microns.

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.

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.

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.