Hexagonal strontium ferrite powder, magnetic recording medium, and magnetic recording and reproducing apparatus

Patent metadata

Field	Value
Publication number	US-11705156-B2
Application number	US-202117542561-A
Country	US
Kind code	B2
Filing date	Dec 6, 2021
Priority date	Jan 11, 2019
Publication date	Jul 18, 2023
Grant date	Jul 18, 2023

Abstract

A hexagonal strontium ferrite powder, in which an average particle size is 10.0 to 25.0 nm, a content of one or more kinds of atom selected from the group consisting of a gallium atom, a scandium atom, an indium atom, and an antimony atom is 1.0 to 15.0 atom % with respect to 100.0 atom % of an iron atom, and a coercivity Hc is greater than 2,000 Oe and smaller than 4.000 Oe. A magnetic recording medium including: a non-magnetic support; and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, in which the ferromagnetic powder is the hexagonal strontium ferrite powder. A magnetic recording and reproducing apparatus including this magnetic recording medium.

First claim

What is claimed is:

1. A hexagonal strontium ferrite powder,
wherein an average particle size is 10.0 to 25.0 nm,
a content of one or more kinds of atom selected from the group consisting of a gallium atom, a scandium atom, an indium atom, and an antimony atom is 1.0 to 15.0 atom % with respect to 100.0 atom % of an iron atom, and
a coercivity Hc is greater than 2,000 Oe and smaller than 4,000 Oe, and
which is a ferromagnetic powder for magnetic recording.

2. The hexagonal strontium ferrite powder according to claim 1 , wherein a mass magnetization σs is equal to or greater than 41 A·m 2 /kg.

3. The hexagonal strontium ferrite powder according to claim 1 , comprising:
a gallium atom.

4. The hexagonal strontium ferrite powder according to claim 1 , comprising:
a scandium atom.

5. The hexagonal strontium ferrite powder according to claim 1 , comprising:
an indium atom.

6. The hexagonal strontium ferrite powder according to claim 1 , comprising:
an antimony atom.

7. The hexagonal strontium ferrite powder according to claim 1 , further comprising:
an aluminum atom.

8. The hexagonal strontium ferrite powder according to claim 1 , further comprising:
a neodymium atom.

9. The hexagonal strontium ferrite powder according to claim 1 ,
wherein the hexagonal strontium ferrite powder has a magnetoplumbite type crystal structure.

10. The hexagonal strontium ferrite powder according to claim 1 ,
wherein the content of the one or more kinds of atom selected from the group consisting of a gallium atom, a scandium atom, an indium atom, and an antimony atom is 1.0 to 12.0 atom % with respect to 100.0 atom % of an iron atom.

11. The hexagonal strontium ferrite powder according to claim 10 , comprising:
a gallium atom.

12. The hexagonal strontium ferrite powder according to claim 10 , comprising:
a scandium atom.

13. The hexagonal strontium ferrite powder according to claim 10 , comprising:
an indium atom.

14. The hexagonal strontium ferrite powder according to claim 10 , comprising:
an antimony atom.

15. The hexagonal strontium ferrite powder according to claim 10 , further comprising:
an aluminum atom.

16. The hexagonal strontium ferrite powder according to claim 10 , further comprising:
a neodymium atom.

Assignees

• Fujifilm Corp

Inventors

• Naoi Kenji
• Shirata Masashi

Classifications

• G11B5/70678 Primary

  Ferrites · CPC title

• C01G49/009

  Compounds containing iron, with or without oxygen or hydrogen, and containing two or more other elements · CPC title

• C01G49/0018

  Mixed oxides or hydroxides, (C01G49/0009 takes precedence) · CPC title

• C01G49/0054

  containing one rare earth metal, yttrium or scandium · CPC title

• G11B5/7013

  characterised by the dispersing agent · CPC title