HEXAGONAL FERRITE MAGNETIC PARTICLES, MAGNETIC RECORDING POWDER, AND MAGNETIC RECORDING MEDIUM

• US 20140295214A1
• Filed: 03/25/2014
• Published: 10/02/2014
• Est. Priority Date: 03/26/2013
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: TADA, Toshio, SUZUKI, Hiroyuki, SHIMIZU, Osamu
• Granted Patent: US 9,818,517 B2
• Time in Patent Office: Days
• US Class Current: 428/842.3
• CPC Class Codes: G11B 5/70615 containing Fe metal or alloys G11B5/70621 takes precedence
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: H01F 1/11 in the form of particles for magnetic record carriers G11B5/70626

Abstract

Hexagonal ferrite magnetic particles have an activation volume ranging from 1,000 nm³ to 1,500 nm³, and ΔE_10%/kT, thermal stability at 10% magnetization reversal, is equal to or greater than 40.

Claims

1. Hexagonal ferrite magnetic particles, which have:

an activation volume ranging from 1,000 nm³ to 1,500 nm³, and

Δ

E_10%/kT, thermal stability at 10% magnetization reversal, is equal to or greater than 40.

2. The hexagonal ferrite magnetic particles according to claim 1, which have a coercive force ranging from 175 kA/m to 400 kA/m.

3. The hexagonal ferrite magnetic particles according to claim 1, which exhibit a switching field distribution, SFD, ranging from 0.2 to 0.8.

4. The hexagonal ferrite magnetic particles according to claim 2, which exhibit a switching field distribution, SFD, ranging from 0.2 to 0.8.

5. The hexagonal ferrite magnetic particles according to claim 1, which comprise 1.5 atomic percent to 20 atomic percent of Al relative to Fe.

6. The hexagonal ferrite magnetic particles according to claim 2, which comprise 1.5 atomic percent to 20 atomic percent of Al relative to Fe.

7. The hexagonal ferrite magnetic particles according to claim 3, which comprise 1.5 atomic percent to 20 atomic percent of Al relative to Fe.

8. The hexagonal ferrite magnetic particles according to claim 4, which comprise 1.5 atomic percent to 20 atomic percent of Al relative to Fe.

9. Magnetic recording powder, which comprised of the hexagonal ferrite magnetic particles according to claim 1.

10. A magnetic recording medium comprising a magnetic layer comprising ferromagnetic material and binder on a nonmagnetic support, wherein

the ferromagnetic material comprises the hexagonal ferrite magnetic particles according to claim 1.

11. A magnetic recording medium comprising a magnetic layer comprising ferromagnetic material and binder on a nonmagnetic support, wherein

the ferromagnetic material comprises the hexagonal ferrite magnetic particles according to claim 2.

12. A magnetic recording medium comprising a magnetic layer comprising ferromagnetic material and binder on a nonmagnetic support, wherein

the ferromagnetic material comprises the hexagonal ferrite magnetic particles according to claim 3.

13. A magnetic recording medium comprising a magnetic layer comprising ferromagnetic material and binder on a nonmagnetic support, wherein

the ferromagnetic material comprises the hexagonal ferrite magnetic particles according to claim 3.

14. A magnetic recording medium comprising a magnetic layer comprising ferromagnetic material and binder on a nonmagnetic support, wherein

the ferromagnetic material comprises the hexagonal ferrite magnetic particles according to claim 5.

15. A magnetic recording medium comprising a magnetic layer comprising ferromagnetic material and binder on a nonmagnetic support, wherein

the ferromagnetic material comprises the hexagonal ferrite magnetic particles according to claim 6.

16. A magnetic recording medium comprising a magnetic layer comprising ferromagnetic material and binder on a nonmagnetic support, wherein

the ferromagnetic material comprises the hexagonal ferrite magnetic particles according to claim 7.

17. A magnetic recording medium comprising a magnetic layer comprising ferromagnetic material and binder on a nonmagnetic support, wherein

the ferromagnetic material comprises the hexagonal ferrite magnetic particles according to claim 8.