Hexagonal ferrite magnetic particle and method of manufacturing the same, and magnetic recording medium

Patent metadata

Field	Value
Publication number	US-9251833-B2
Application number	US-201314022554-A
Country	US
Kind code	B2
Filing date	Sep 10, 2013
Priority date	Mar 31, 2010
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

An aspect of the present invention relates to a method of manufacturing a hexagonal ferrite magnetic particle comprising melting an Al-containing starting material mixture to prepare a melt and quenching the melt to obtain an amorphous material; subjecting the amorphous material to heat treatment to cause a hexagonal ferrite magnetic particle to precipitate in a product obtained by the heat treatment; collecting a hexagonal ferrite magnetic particle by subjecting the product to treatment with an acid and washing, wherein the hexagonal ferrite magnetic particle collected has a particle size ranging from 15 to 30 nm, comprises 0.6 to 8.0 weight percent of Al, based on Al 2 O 3 conversion, relative to a total weight of the particle, and Al adheres to a surface of the hexagonal ferrite magnetic particle.

First claim

What is claimed is:

1. A hexagonal ferrite magnetic particle prepared by a method of manufacturing a hexagonal ferrite magnetic particle comprising:
melting an Al-containing starting material mixture to prepare a melt and quenching the melt to obtain an amorphous material;
subjecting the amorphous material to heat treatment to cause a hexagonal ferrite magnetic particle to precipitate in a product obtained by the heat treatment;
collecting a hexagonal ferrite magnetic particle by subjecting the product to treatment with an acid and washing, wherein the hexagonal ferrite magnetic particle collected has a particle size ranging from 15 to 30 nm, comprises 0.6 to 8.0 weight percent of Al, based on Al 2 O 3 conversion, relative to a total weight of the particle, and Al adheres to a surface of the hexagonal ferrite magnetic particle, said particle being comprised of a primary particle of hexagonal ferrite to whose surface Al adheres.

2. The hexagonal ferrite magnetic particle according to claim 1 , which has a coercive force ranging from 159 to 318 kA/m.

3. The hexagonal ferrite magnetic particle according to claim 1 , on whose surface Al is present as an oxide.

4. The hexagonal ferrite magnetic particle according to claim 1 , which has a specific surface area ranging from 50 to 100 m 2 /g.

5. The hexagonal ferrite magnetic particle according to claim 1 , which is a barium ferrite magnetic particle.

6. 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 ferrite magnetic particle according to claim 1 .

Assignees

• Fujifilm Corp

Inventors

• Suzuki Hiroyuki
• Yamazaki Nobuo

Classifications

• C04B2235/767

  Hexagonal symmetry, e.g. beta-Si3N4, beta-Sialon, alpha-SiC or hexa-ferrites · CPC title

• C01P2006/12

  Surface area · CPC title

• C04B2235/3275

  Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite · CPC title

• C04B35/2683

  Other ferrites containing alkaline earth metals or lead · CPC title

• C04B35/62665

  Flame, plasma or melting treatment · CPC title