Sony Corporation

Sony Group Corporation

Masaru Terakawa

Minoru Yamaga

Katsunori Maeshima

Yoichi Kanemaki

Eiji Nakashio

Tomoe Sato

Nobuyuki Sasaki

Masafumi Nakaya

Takeshi Takahashi

Atsushi Muramatsu

Kazuya Hashimoto

Jun Hashimoto

Takashi Kataguchi

Natsuki Ichise

Satoru Abe

Yuta Akimoto

Natsuki Toyosawa

Hiroyuki Kobayashi

Takanobu Iwama

Jun Takahashi

Futoshi Sasaki

Norikatsu Fujisawa

Hikaru Terui

Taikei Enomoto

Atsushi Muramatu

Yuuichi Masuzawa

Provided is a magnetic recording medium including: a support body; a base layer containing carbon particle powder and metal-containing particle powder; and a recording layer. In a recording surface, a maximum indentation depth h is 85≤h≤140, and a ratio d of a permanent strain to an elastic recovery (permanent strain/elastic recovery) is 0.95≤d≤1.25.

Magnetic recording medium

Provided is a magnetic recording medium configured to achieve higher density recording. The magnetic recording medium has a tape-like shape, and includes: a base containing polyester as a main constituent; and a magnetic layer provided on the base, including a plurality of magnetic powders, and configured to record a data signal. An average thickness of the magnetic recording medium is 5.6 μm or less. An average thickness of the base is 4.2 μm or less. An average thickness of the magnetic layer is 90 nm or less. An average aspect ratio of the magnetic powders is 1.0 or greater and 3.0 or less. A coercivity in a perpendicular direction is 3000 oersted or less. A rate of a coercivity in a longitudinal direction to the coercivity in the perpendicular direction is 0.8 or less. The magnetic layer includes a lubricant. An entire BET specific surface area of the magnetic recording medium from which the lubricant has been removed is 2.5 m/g or greater.

Magnetic recording medium having a particular specific surface area, magnetic recording and reproducing apparatus, and magnetic recording medium cartridge

A magnetic recording medium is a tape-shaped magnetic recording medium that has a recording layer including an ε-iron oxide particle. An area ratio R(=(S/S)×100) of a total area Sof an SFD curve of the recording layer in a perpendicular direction and an area Sof the SFD curve in which a coercivity Hc is in a range from −500 [Oe]≤Hc≤500 [Oe] is equal to or less than 5.5%.

Provided is a magnetic recording medium capable of implementing higher-density recording. This magnetic recording medium includes a substrate containing a polyester and a magnetic layer disposed on the substrate, including a plurality of types of magnetic powder. A surface of the magnetic layer has an arithmetic average roughness Ra of 2.5 nm or less. PSD to a spatial wavelength of 5 &#x3bc;m is 2.5 &#x3bc;m or less. The magnetic layer has an average thickness of 90 nm or less. The magnetic powder has an average aspect ratio of 1.0 or more and 3.0 or less. A coercive force in a perpendicular direction is 3000 oersted or less. A ratio of a coercive force in a longitudinal direction to the coercive force in the perpendicular direction is 0.8 or less. A half-value width of an isolated waveform in a reproduced waveform of a data signal is 200 nm or less.

Magnetic recording medium including magnetic layer having magnetic powder, magnetic recording/reproducing device, and magnetic recording medium cartridge

[Solving Means] A method of producing a magnetic powder includes: coating a surface of each of silica-coated precursor particles with at least one type of coating agent of a metal chloride or a sulfate; and firing the precursor particles coated with the coating agent.

Method of producing magnetic powder and method of producing magnetic recording medium

Provided is a magnetic recording medium having a recording track width of 2 &#x3bc;m or less, including: a recording layer containing a powder of particles containing &#x3b5; iron oxide, in which a squareness ratio measured in a transport direction is 30% or less, a squareness ratio S1 measured in the transport direction and a squareness ratio S2 measured in a width direction satisfy a relationship S1&#x2265;S2, a coercive force is 220 kA/m or greater and 310 kA/m or less, an activation volume is 8000 nmor less, and in a switching field distribution (SFD) curve, a peak ratio X/Y of a main peak height X and a height Y of a sub-peak near zero magnetic field is 3.0 or greater.

A magnetic recording medium is provided and includes a layer structure including a magnetic layer, a non-magnetic layer, and a base layer in order, in which an average thickness tof the magnetic recording medium is 4.0 &#x3bc;m&#x2264;t&#x2264;5.3 &#x3bc;m, a dimensional variation &#x394;w in a width direction of the magnetic recording medium to tension change in a longitudinal direction of the magnetic recording medium is 680 ppm/N&#x2264;&#x394;w&#x2264;2000 ppm/N, and an average thickness tof the non-magnetic layer is t&#x2264;1.0 &#x3bc;m.

Magnetic recording medium having controlled dimensional variation

An object of the present disclosure is to provide a magnetic recording medium excellent in electro-magnetic conversion characteristic and thermal stability. The present disclosure provides a tape-shaped magnetic recording medium including: a substrate; and a magnetic layer provided over the substrate and including a magnetic powder, in which the magnetic layer has an average thickness of equal to or less than 90 nm, the magnetic powder has an average aspect ratio of from 1.0 to 3.0, the magnetic powder has an average particle volume of equal to or less than 2,300 nm, a coercive force Hc1 in a vertical direction of the magnetic recording medium is equal to or less than 4,500 Oe, a coercive force Hc2 in a longitudinal direction of the magnetic recording medium and the coercive force Hc1 satisfy a relation of Hc2/Hc1&#x2264;0.8, and the ratio Hrp/Hc1 of a residual coercive force Hrp of the magnetic recording medium measured using a pulsed magnetic field and the coercive force Hc1 is equal to or less than 2.0.

A magnetic recording medium, which is used in a recording and playback device in which the shortest recording wavelength is 75 nm or less, in which the magnetic recording medium has a recording layer including powder of &#x3b5;-iron oxide-containing particles, the average particle size of the particles is 22 nm or less, the coercive force He is 220 kA/m or more and 320 kA/m or less, and the non linear transition shift is 20% or less.

Magnetic recording medium having -iron oxide-containing particles

A cobalt ferrite magnetic powder includes magnetic particles that have a uniaxial crystal magnetic anisotropy and contain cobalt ferrite. A peak top 2&#x3b8; of a (3, 1, 1) plane determined by powder X-ray diffractometry using a CoK&#x3b1; ray is 41.3&#xb0; or more and 41.5&#xb0; or less. Some Cos contained in the magnetic particles are substituted with at least one selected from the group consisting of Zn, Ge, and a transition metal element other than Fe.

Cobalt ferrite magnetic powder, method of producing the same, and magnetic recording medium

A method of producing a magnetic powder includes: performing heat treatment on first particles that contain triiron tetraoxide to prepare second particles that contain &#x3b5;-iron oxide.

Method of producing a magnetic powder and method of producing a magnetic recording medium

A magnetic recording medium used on a record/playback device with a minimum recording wavelength or 50 nm or shorter, the magnetic recording medium including a magnetic layer that contains a spinel-type ferrite magnetic powder, the magnetic layer having an average thickness of 85 nm or smaller, and the magnetic layer having a saturation flux density of 1600 Gauss or larger and 2000 Gauss or smaller.

Magnetic recording medium having controlled saturation flux density

A magnetic recording medium includes a nonmagnetic support body, and a magnetic layer containing magnetic powder, in which the magnetic powder contains &#x3b5;-FeOcrystal (including a case of substituting a portion of Fe site with a metal element M), a product of residual magnetization and a thickness of the magnetic layer is from 0.5 mA to 6.0 mA, and a squareness ratio which is measured in a longitudinal direction of the magnetic layer is 0.3 or less.

A method for producing a magnetic powder includes performing a reduction treatment on the surface of particles including a hard magnetic material to form core-shell particles each having a shell portion including a soft magnetic material.

Magnetic powder, method for production thereof, and magnetic recording medium

The magnetic recording medium includes a long substrate body, and a magnetic layer including a powder of cubic crystal ferrite magnetic particles. The sum of a squareness ratio in the longitudinal direction and a squareness ratio in the vertical direction is 1.2 or more, and the difference of the squareness ratio in the longitudinal direction and the squareness ratio in the vertical direction is 0.15 or more.

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Miyagi, Japan

Masaru Terakawa