MAGNETIC RECORDING MEDIUM

• US 20150111066A1
• Filed: 10/15/2014
• Published: 04/23/2015
• Est. Priority Date: 10/22/2013
• Status: Abandoned Application

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Terakawa, Masaru, Yamaga, Minoru, Kanemaki, Yoichi
• Application Number:
  US14/514,518
• Publication Number:
  US 20150111066A1
• Time in Patent Office: Days
• US Class Current: 428/836.2
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/70642 iron oxides

Abstract

A magnetic recording medium includes a nonmagnetic support body, and a magnetic layer containing magnetic powder, in which the magnetic powder contains ε-Fe₂O₃ crystal (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.

Claims

1. A magnetic recording medium comprising:

a nonmagnetic support body; and

a magnetic layer containing magnetic powder,

wherein the magnetic powder contains ε

-Fe₂O₃ crystal (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.

2. The magnetic recording medium according to claim 1,

wherein the thickness of the magnetic layer is from 30 nm to 100 nm.

3. The magnetic recording medium according to claim 1,

wherein an spontaneous magnetization amount of the magnetic powder is from 5 emu/g to 25 emu/g.

4. The magnetic recording medium according to claim 1,

wherein coersive force of the magnetic layer is from 2000 Oe to 4500 Oe.

5. The magnetic recording medium according to claim 1,

wherein physical volume of the magnetic powder is from 800 nm³ to 4000 nm³.

6. The magnetic recording medium according to claim 1,

wherein a filling rate of the magnetic powder is 30% or more.

7. The magnetic recording medium according to claim 1,

wherein a magnetic resistance effect type head of a tunnel type is used as a reproduction head.