Magnetic recording medium

Patent metadata

Field	Value
Publication number	US-10614847-B2
Application number	US-201715855412-A
Country	US
Kind code	B2
Filing date	Dec 27, 2017
Priority date	Dec 28, 2016
Publication date	Apr 7, 2020
Grant date	Apr 7, 2020

Abstract

In a magnetic recording medium according to the present invention, if a straight line W having a length of 500 nm and a width of 15 nm is displayed parallel to a width direction of the magnetic layer and a straight line L having a length of 500 nm and a width of 15 nm is displayed parallel to a longitudinal direction of the magnetic layer, the number of magnetic particles that intersect the straight line W is N1, and the number of magnetic particles that intersect the straight line L is N2, then, a relationship of N1/0.5>60 and N2/0.5>60 is established where N1/0.5 is the number of magnetic particles per micrometer obtained by dividing N1 by 0.5 μm and N2/0.5 is the number of magnetic particles per micrometer obtained by dividing N2 by 0.5 μm.

First claim

What is claimed is:

1. A magnetic recording medium comprising:
a nonmagnetic support body; and
a magnetic layer containing magnetic particles,
wherein 0.0013 μT·m<Mr·t<0.0032 μT·m is satisfied where Mr is a residual magnetic flux density in a thickness direction of the magnetic layer and t is an average thickness of the magnetic layer,
a squareness ratio in the thickness direction of the magnetic layer is 0.65 or more,
if a straight line W having a length of 500 nm and a width of 15 nm is displayed parallel to a width direction of the magnetic layer and a straight line L having a length of 500 nm and a width of 15 nm is displayed parallel to a longitudinal direction of the magnetic layer, on an image obtained by observing a surface of the magnetic layer using a scanning electron microscope at 10 k-fold magnification,
the straight line W does not intersect a particle having a particle diameter of 50 nm or more and a gap having a maximum width of 50 nm or more on the image, and on the image, the number of magnetic particles that intersect the straight line W is N1, and
the straight line L does not intersect a particle having a particle diameter of 50 nm or more and a gap having a maximum width of 50 nm or more on the image, and on the image, the number of magnetic particles that intersect the straight line L is N2,
then, a relationship of N1/0.5>60 and N2/0.5>60 is established where N1/0.5 is the number of magnetic particles per micrometer obtained by dividing N1 by 0.5 μm and N2/0.5 is the number of magnetic particles per micrometer obtained by dividing N2 by 0.5 μm.

2. The magnetic recording medium according to claim 1 ,
wherein if a length of magnetization in the width direction of the magnetic layer is set to 1 μm or less, the length being a length of magnetization of a signal recorded in the magnetic layer, reproduction is performed by a TMR head.

3. The magnetic recording medium according to claim 1 ,
wherein the magnetic particles are made of ε-iron oxide.

4. The magnetic recording medium according to claim 3 ,
wherein an average particle diameter of the magnetic particles made of the ε-iron oxide is 15 nm or less.

5. The magnetic recording medium according to claim 1 ,
wherein a magnetic coercive force in the thickness direction of the magnetic layer is 3000 oersteds [Oe] or more.

6. The magnetic recording medium according to claim 1 ,
wherein when spacing on a surface of the magnetic layer is measured using a TSA (tape spacing analyzer) after the surface of the magnetic layer is cleaned using n-hexane, a value of the spacing is 5 nm or more and 12 nm or less.

7. The magnetic recording medium according to claim 1 ,
wherein a thickness of the magnetic layer is 30 nm or more and 200 nm or less.

Assignees

• Maxell Holdings Ltd

Inventors

• Kawakami Shinji
• Hiroi Toshio
• Fujita Masao

Classifications

• G11B5/714 Primary

  characterised by the dimension of the magnetic particles · CPC title

• G11B5/70642

  iron oxides · CPC title

• G11B5/70615

  containing Fe metal or alloys (G11B5/70621 takes precedence) · CPC title

• G11B5/70

  on a base layer · CPC title