HIGH RECORDING DENSITY MAGNETIC RECORDING MEDIUM AND RECORDING/REPRODUCTION MECHANISM FOR THE SAME

• US 20180350398A1
• Filed: 06/04/2018
• Published: 12/06/2018
• Est. Priority Date: 06/05/2017
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Maxell Holdings, Ltd.
• Inventors: KAWAKAMI, Shinji, KAWAKITA, Toshio, FUJITA, Masao
• Granted Patent: US 10,861,487 B2
• Time in Patent Office: Days
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11B 5/68 comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/70642 iron oxides
• CPC Class Codes: G11B 5/714 characterised by the dimension of the magnetic particles
• CPC Class Codes: G11B 5/82 Disk carriers

Abstract

A refractive index nL and an attenuation rate kL of a magnetic layer are obtained by irradiating linearly polarized light at an irradiation angle of 70° from a lengthwise direction of the magnetic layer to the surface of the magnetic layer, and a vertical reflectance RL during vertical incidence of the linearly polarized light in the lengthwise direction is obtained based on nL and kL. A refractive index nT and an attenuation rate kT of the magnetic layer are obtained by irradiating linearly polarized light at an irradiation angle of 70° from a width direction of the magnetic layer to the surface of the magnetic layer, and a vertical reflectance RT during vertical incidence of the linearly polarized light in the width direction is obtained from nT and kT. If a variation rate A (%) of RL and RT is A=|RL/RT−1|×100, the relationship A≤10% is established.

Claims

1. A high recording density magnetic recording medium comprising a nonmagnetic support body and a magnetic layer including magnetic particles, wherein

an average particle diameter of the magnetic particles is 17 nm or less,

a refractive index nL and an attenuation rate kL of the magnetic layer are obtained by irradiating linearly polarized light at an irradiation angle of 70°

from a lengthwise direction of the magnetic layer to the surface of the magnetic layer, and a vertical reflectance RL during vertical incidence of the linearly polarized light in the lengthwise direction is obtained from nL and kL,

a refractive index nT and an attenuation rate kT of the magnetic layer are obtained by irradiating linearly polarized light at an irradiation angle of 70°

from a width direction of the magnetic layer to the surface of the magnetic layer, and a vertical reflectance RT during vertical incidence of the linearly polarized light in the width direction is obtained from nT and kT, and

if a variation rate A (%) of RL and RT is A=|RL/RT−

1|×

100,

a relationship A≤

10% is established.

2. The high recording density magnetic recording medium according to claim 1, wherein if a length of magnetization of a signal recorded on the magnetic layer is 1 μ

m or less, the length of magnetization being in the width direction of the magnetic layer, reproduction is performed with a TMR head.

3. The high recording density magnetic recording medium according to claim 1, wherein 0.0013 μ

T·

m<

Mr·

t<

0.0032 μ

T·

m is satisfied, where a residual magnetic flux density in a thickness direction of the magnetic layer is Mr and an average thickness of the magnetic layer is t.

4. The high recording density magnetic recording medium according to claim 1, wherein a squareness ratio in the thickness direction of the magnetic layer is 0.65 or more.

5. The high recording density magnetic recording medium according to claim 1, wherein the magnetic particles contain ε

-iron oxide particles.

6. The high recording density 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.

7. The high recording density magnetic recording medium according to claim 1, wherein when the surface of the magnetic layer is cleaned using n-hexane and thereafter spacing on the surface of the magnetic layer is measured using a TSA (Tape Spacing Analyzer), a value of the spacing is 5 nm or more and 12 nm or less.

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

9. A recording/reproduction mechanism for a high recording density magnetic recording medium, comprising:

the high recording density magnetic recording medium according to claim 1, and a TMR head.