HEXAGONAL BARIUM FERRITE MAGNETIC PARTICLE AND METHOD OF MANUFACTURING THE SAME, AND MAGNETIC RECORDING MEDIUM

• US 20120177951A1
• Filed: 01/05/2012
• Published: 07/12/2012
• Est. Priority Date: 01/06/2011
• Status: Abandoned Application

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: YAMAZAKI, Nobuo, SUZUKI, Hiroyuki
• Application Number:
  US13/344,354
• Publication Number:
  US 20120177951A1
• Time in Patent Office: Days
• US Class Current: 428/842.8
• 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

An aspect of the present invention relates to a hexagonal barium ferrite magnetic particle, wherein, relative to 100 atom percent of a Fe content, an Al content ranges from 1.5 to 15 atom percent, a combined content of a divalent element and a pentavalent element ranges from 1.0 to 10 atom percent, an atomic ratio of a content of the divalent element to a content of the pentavalent element is greater than 2.0 but less than 4.0, and an activation volume ranges from 1,300 to 1,800 nm³.

Claims

1. A hexagonal barium ferrite magnetic particle, wherein, relative to 100 atom percent of a Fe content, an Al content ranges from 1.5 to 15 atom percent, a combined content of a divalent element and a pentavalent element ranges from 1.0 to 10 atom percent, an atomic ratio of a content of the divalent element to a content of the pentavalent element is greater than 2.0 but less than 4.0, and an activation volume ranges from 1,300 to 1,800 nm³.

2. The hexagonal barium ferrite magnetic particle according to claim 1, which has a saturation magnetization, as, of equal to or greater than 50 A·

m²/kg.

3. The hexagonal barium ferrite magnetic particle according to claim 1, which has a thermal stability in the form of KuV/kT of equal to or greater than 60, wherein Ku denotes an anisotropy constant, V denotes an activation volume, k denotes a Boltzmann constant, and T denotes an absolute temperature.

4. The hexagonal barium ferrite magnetic particle according to claim 1, wherein the divalent element is selected from the group consisting of Co and Zn.

5. The hexagonal barium ferrite magnetic particle according to claim 1, wherein the pentavalent element is selected from the group consisting of V and Nb.

6. The hexagonal barium ferrite magnetic particle according to claim 1, which is employed for magnetic recording.

7. A method of manufacturing a hexagonal barium ferrite magnetic particle, which comprises:

providing a starting material mixture wherein, relative to 100 atom percent of a Fe content, an Al content ranges from 1.5 to 15 atom percent, a combined content of a divalent element and a pentavalent element ranges from 1.0 to 10 atom percent, and an atomic ratio of a content of the divalent element to a content of the pentavalent element is greater than 2.0 but less than 4.0; and

conducting a glass crystallization method with the use of the starting material mixture to form the hexagonal barium ferrite magnetic particle according to claim 1.

8. The method of manufacturing a hexagonal barium ferrite magnetic particle according to claim 7, wherein the divalent element is selected from the group consisting of Co and Zn.

9. The method of manufacturing a hexagonal barium ferrite magnetic particle according to claim 7, wherein the pentavalent element is selected from the group consisting of V and Nb.

10. The method of manufacturing a hexagonal barium ferrite magnetic particle according to claim 7, wherein the hexagonal barium ferrite magnetic particle formed has a saturation magnetization, σ

s, of equal to or greater than 50 A·

m²/kg.

11. The method of manufacturing a hexagonal barium ferrite magnetic particle according to claim 7, wherein the hexagonal barium ferrite magnetic particle formed has a thermal stability in the form of KuV/kT of equal to or greater than 60, wherein Ku denotes an anisotropy constant, V denotes an activation volume, k denotes a Boltzmann constant, and T denotes an absolute temperature.

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

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

13. The magnetic recording medium according to claim 12, wherein the hexagonal barium ferrite magnetic particle contained in the magnetic layer has a saturation magnetization, as, of equal to or greater than 50 A·

m²/kg.

14. The magnetic recording medium according to claim 12, wherein the hexagonal barium ferrite magnetic particle contained in the magnetic layer has a thermal stability in the form of KuV/kT of equal to or greater than 60, wherein Ku denotes an anisotropy constant, V denotes an activation volume, k denotes a Boltzmann constant, and T denotes an absolute temperature.

15. The magnetic recording medium according to claim 12, wherein the divalent element contained in the hexagonal barium ferrite magnetic particle is selected from the group consisting of Co and Zn.

16. The magnetic recording medium according to claim 12, wherein the pentavalent element contained in the hexagonal barium ferrite magnetic particle is selected from the group consisting of V and Nb.