Magnetic recording medium

Patent metadata

Field	Value
Publication number	US-2021350827-A1
Application number	US-201917272159-A
Country	US
Kind code	A1
Filing date	Sep 5, 2019
Priority date	Sep 5, 2018
Publication date	Nov 11, 2021
Grant date	—

Abstract

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.

First claim

1 . A magnetic recording medium used on a record/playback device with a minimum recording wavelength or 50 nm or shorter, the magnetic recording medium comprising:
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.

2 . The magnetic recording medium according to claim 1 , wherein the spinel-type ferrite magnetic powder has uniaxial magnetic anisotropy.

3 . The magnetic recording medium according to claim 1 , wherein the spinel-type ferrite magnetic powder is oriented in a thickness direction of the magnetic layer.

4 . The magnetic recording medium according to claim 1 , wherein
the spinel-type ferrite magnetic powder contains a cubic or nearly cubic magnetic particle, and a square face of the magnetic particle exposes out from the surface of the magnetic layer.

5 . The magnetic recording medium according to claim 4 , wherein the surface of the magnetic layer has spread thereon the square faces of the magnetic particle.

6 . The magnetic recording medium according to claim 1 , wherein the spinel-type ferrite magnetic powder is cobalt-ferrite magnetic powder.

7 . The magnetic recording medium according to claim 1 , wherein the spinel-type ferrite magnetic powder has an average size of 25 nm or smaller.

8 . The magnetic recording medium according to claim 1 , having an average thickness of 5.6 μm or smaller.

9 . The magnetic recording medium according to claim 1 , further comprising
an underlayer arranged below the magnetic layer, wherein average thicknesses of the magnetic layer and the underlayer total 1.1 μm or smaller.

10 . The magnetic recording medium according to claim 1 , having a squareness ratio in the vertical direction of 65% or larger.

11 . The magnetic recording medium according to claim 1 , wherein
the magnetic recording medium has an elongated form, and the magnetic recording medium has a squareness ratio in a longitudinal direction of 35% or smaller.

12 . The magnetic recording medium according to claim 1 , wherein
the magnetic recording medium has an elongated form, and the magnetic recording medium has a coercive force in a longitudinal direction of 2000 Oe or smaller.

Assignees

• Sony Corp

Inventors

• Terakawa Masaru
• Yamaga Minoru

Classifications

• G11B5/7356

  comprising non-magnetic particles in the back layer, e.g. particles of TiO2, ZnO or SiO2 · CPC title

• G11B5/70678 Primary

  Ferrites · CPC title

• G11B5/73

  Base layers {, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer} · CPC title

• G11B5/706

  characterised by the composition of the magnetic material · CPC title

• G11B5/714

  characterised by the dimension of the magnetic particles · CPC title