Magnetic recording medium

Patent metadata

Field	Value
Publication number	US-2019295584-A1
Application number	US-201716321291-A
Country	US
Kind code	A1
Filing date	Nov 17, 2017
Priority date	Dec 20, 2016
Publication date	Sep 26, 2019
Grant date	—

Abstract

A magnetic recording medium is used in a recording/reproduction apparatus having a shortest recording wavelength of not more than 75 nm, the magnetic recording medium including a recording layer that contains a powder of particles containing ε-iron oxide, in which a squareness ratio measured in a traveling direction of the magnetic recording medium is not more than 30%, a ratio (Dmax/Dmin) of an average longest diameter Dmax of the particles to an average shortest diameter Dmin of the particles satisfies a relationship of 1.0≤(Dmax/Dmin)≤1.1, an average thickness δmag of the recording layer is not more than 100 nm, and a ratio (δmag/Dmin) of the average thickness δmag of the recording layer to the average shortest diameter Dmin of the particles satisfies a relationship of δmag/Dmin≤5.

First claim

1 . A magnetic recording medium that is used in a recording/reproduction apparatus having a shortest recording wavelength of not more than 75 nm, the magnetic recording medium comprising:
a recording layer that contains a powder of particles containing ε-iron oxide, wherein a squareness ratio measured in a traveling direction of the magnetic recording medium is not more than 30%, a ratio (D max /D min ) of an average longest diameter D max of the particles to an average shortest diameter D min of the particles satisfies a relationship of 1.0≤(D max /D min )≤1.1, an average thickness δ mag of the recording layer is not more than 100 nm, and a ratio (δ mag /D min ) of the average thickness δ mag of the recording layer to the average shortest diameter D min of the particles satisfies a relationship of δ mag /D min ≤5.

2 . The magnetic recording medium according to claim 1 , wherein
each of the particles has a spherical shape or a substantially spherical shape.

3 . The magnetic recording medium according to claim 1 , wherein
each of the particles has a cubic shape or a substantially cubic shape.

4 . The magnetic recording medium according to claim 1 , wherein
each of the particles has a core-shell structure.

5 . The magnetic recording medium according to claim 1 , wherein
each of the particles includes
a core portion containing ε-iron oxide, and
a shell portion containing a soft magnetic material.

6 . The magnetic recording medium according to claim 5 , wherein
each of the particles further includes an oxide coating film provided on the shell portion.

7 . The magnetic recording medium according to claim 1 , wherein
the squareness ratio measured in the traveling direction of the magnetic recording medium is not more than 25%.

8 . The magnetic recording medium according to claim 1 , wherein
an average thickness δ mag of the recording layer is not more than 80 nm.

9 . The magnetic recording medium according to claim 1 , wherein
a ratio (δ mag /D min ) of an average thickness δ mag of the recording layer to an average shortest diameter D min of the particles satisfies a relationship of δ mag /D min ≤4.5.

10 . The magnetic recording medium according to claim 1 , wherein
each of the particles further contains metal other than iron.

11 . The magnetic recording medium according to claim 1 , wherein
an activation volume V act is not more than 5000 nm 3 .

12 . The magnetic recording medium according to claim 1 , wherein
an activation volume V act is not more than 3000 nm 3 .

13 . The magnetic recording medium according to claim 1 , wherein
the recording/reproduction apparatus includes a ring-type head as a recording head.

14 . The magnetic recording medium according to claim 1 , which is perpendicular magnetic recording-type magnetic recording medium.

Assignees

• Sony Corp

Inventors

• Terakawa Masaru
• Kanemaki Yoichi
• Yamaga Minoru

Classifications

• G11B5/712 Primary

  characterised by the surface treatment or coating of magnetic particles · CPC title

• G11B5/70605 Primary

  metals or alloys · CPC title

• G11B5/714

  characterised by the dimension of the magnetic particles · CPC title

• G11B5/70

  on a base layer · CPC title

• G11B5/70642

  iron oxides · CPC title