HEXAGONAL FERRITE POWDER AND MAGNETIC RECORDING MEDIUM

• US 20170287517A1
• Filed: 03/31/2017
• Published: 10/05/2017
• Est. Priority Date: 03/31/2016
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: HOSOYA, Yoichi, SHIRATA, Masashi
• Granted Patent: US 10,373,638 B2
• Time in Patent Office: Days
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• 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: G11B 5/714 characterised by the dimension of the magnetic particles
• CPC Class Codes: G11B 5/78 Tape carriers
• CPC Class Codes: H01F 1/0063 in a non-magnetic matrix, e.g. granular solids granular films H01F10/007
• CPC Class Codes: H01F 1/11 in the form of particles for magnetic record carriers G11B5/70626

Abstract

Hexagonal ferrite powder has an average particle size falling within a range of 10 nm to 50 nm, a switching field distribution SFD_{23° C.} measured at a temperature of 23° C. that is less than or equal to 0.80, and a ratio of a switching field distribution SFD_{−190° C.} that is measured at a temperature of −190° C. to the SFD_{23° C.} (SFD_{−190° C.}/SFD_{23° C.}) that is greater than 0.80.

Claims

1. Hexagonal ferrite powder, which has:

an average particle size falling within a range of 10 nm to 50 nm;

a switching field distribution SFD<sub>23°

C.</sub> measured at a temperature of 23°

C. of less than or equal to 0.80; and

a ratio of a switching field distribution SFD<sub>−

190°

C.</sub> that is measured at a temperature of −

190°

C. to the SFD<sub>23°

C.</sub>, SFD<sub>−

190°

C.</sub>/SFD<sub>23°

C.</sub>, of greater than 0.80.

2. The hexagonal ferrite powder according to claim 1,

which has a saturation magnetization of greater than or equal to 30.0 A·

m²/kg.

3. The hexagonal ferrite powder according to claim 1,

which has a coercive force of greater than or equal to 159 kA/m.

4. The hexagonal ferrite powder according to claim 1,

wherein the average particle size falls within a range of 10 nm to 35 nm.

5. The hexagonal ferrite powder according to claim 1,

wherein the SFD_23°

C. is less than or equal to 0.60.

6. The hexagonal ferrite powder according to claim 1,

wherein the SFD_23°

C. falls within a range of 0.10 to 0.60.

7. The hexagonal ferrite powder according to claim 1,

wherein the ratio, SFD₋

190°

C./SFD<sub>23°

C.</sub>, is greater than or equal to 0.90.

8. The hexagonal ferrite powder according to claim 1,

wherein the ratio, SFD₋

190°

C./SFD<sub>23°

C.</sub>, falls within a range of 0.90 to 1.50.

9. The hexagonal ferrite powder according to claim 1,

wherein the SFD_23°

C. falls within a range of 0.10 to 0.60, and the ratio, SFD<sub>−

190°

C.</sub>/SFD<sub>23°

C.</sub>, falls within a range of 0.90 to 1.50.

10. A magnetic recording medium,

which comprises a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support,

wherein the ferromagnetic powder is hexagonal ferrite powder which has:

an average particle size falling within a range of 10 nm to 50 nm;

a switching field distribution SFD<sub>23°

C.</sub> measured at a temperature of 23°

C. of less than or equal to 0.80; and

a ratio of a switching field distribution SFD<sub>−

190°

C.</sub> that is measured at a temperature of −

190°

C. to the SFD<sub>23°

C.</sub>, SFD<sub>−

190°

C.</sub>/SFD<sub>23°

C.</sub>, of greater than 0.80.

11. The magnetic recording medium according to claim 10,

wherein the hexagonal ferrite powder has a saturation magnetization of greater than or equal to 30.0 A·

m²/kg.

12. The magnetic recording medium according to claim 10,

wherein the hexagonal ferrite powder has a coercive force of greater than or equal to 159 kA/m.

13. The magnetic recording medium according to claim 10,

wherein the average particle size of the hexagonal ferrite powder falls within a range of 10 nm to 35 nm.

14. The magnetic recording medium according to claim 10,

wherein the SFD_23°

C. of the hexagonal ferrite powder is less than or equal to 0.60.

15. The magnetic recording medium according to claim 10,

wherein the SFD_23°

C. of the hexagonal ferrite powder falls within a range of 0.10 to 0.60.

16. The magnetic recording medium according to claim 10,

wherein the ratio, SFD₋

190°

C./SFD<sub>23°

C.</sub>, of the hexagonal ferrite powder is greater than or equal to 0.90.

17. The magnetic recording medium according to claim 10,

wherein the ratio, SFD₋

190°

C./SFD<sub>23°

C.</sub>, of the hexagonal ferrite powder falls within a range of 0.90 to 1.50.

18. The magnetic recording medium according to claim 10,

wherein the SFD_23°

C. of the hexagonal ferrite powder falls within a range of 0.10 to 0.60, and the ratio, SFD<sub>−

190°

C.</sub>/SFD<sub>23°

C.</sub>, of the hexagonal ferrite powder falls within a range of 0.90 to 1.50.