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

Patent metadata

Field	Value
Publication number	US-9478331-B2
Application number	US-201313839619-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	Mar 30, 2012
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

An aspect of the present invention relates to a method of manufacturing hexagonal strontium ferrite magnetic powder, which comprises melting a starting material mixture which has a composition, as a composition converted into an oxide, lying within a region enclosed by the following four points:
(a) SrO=48.0 mol %, Fe 2 O 3 =17.2 mol %, B 2 O 3 =34.8 mol %; (b) SrO=55.9 mol %, Fe 2 O 3 =17.7 mol %, B 2 O 3 =26.4 mol %; (c) SrO=41.7 mol %, Fe 2 O 3 =40.9 mol %, B 2 O 3 =17.4 mol %; (d) SrO=36.7 mol %, Fe 2 O 3 =40.1 mol %, B 2 O 3 =23.2 mol %;

in a ternary diagram with SrO, Fe 2 O 3 , which may include an Fe substitution element, and B 2 O 3 as apexes, to provide a melt, and quenching the melt to obtain a solidified product; and heat treating the solidified product to precipitate hexagonal strontium ferrite magnetic particles within the solidified product.

First claim

What is claimed is:

1. A method of manufacturing hexagonal strontium ferrite magnetic powder, which comprises:
melting a starting material mixture which has a composition, as a composition converted into an oxide, lying within a region enclosed by the following three points:
(e) SrO=48.3 mol %, Fe 2 O 3 =17.2 mol %, B 2 O 3 =34.5 mol %;
(f) SrO=55.9 mol %, Fe 2 O 3 =17.7 mol %, B 2 O 3 =26.4 mol %;
(g) SrO=42.8 mol %, Fe 2 O 3 =39.1 mol %, B 2 O 3 =18.1 mol %;
in a ternary diagram with SrO, Fe 2 O 3 , which optionally may include an Fe substitution element, and B 2 O 3 as apexes, to provide a melt, and quenching the melt to obtain a solidified product; and
heat treating the solidified product to precipitate hexagonal strontium ferrite magnetic particles within the solidified product,
wherein:
the heat treatment is conducted by heating and maintaining the solidified product in a temperature region ranging from 600 to 660° C.; and
the heat treatment provides precipitated hexagonal strontium ferrite magnetic particles with an activation volume ranging from 1,000 to 1,383 nm 3 .

2. A method of manufacturing a magnetic recording medium, which comprises:
conducting the method of manufacturing according to claim 1 to provide hexagonal strontium ferrite magnetic powder; and
preparing a magnetic layer with a magnetic coating material which comprises the hexagonal strontium ferrite magnetic powder and a binder, on a nonmagnetic support.

Assignees

• Fujifilm Corp

Inventors

• Yamazaki Nobuo
• Suzuki Hiroyuki

Classifications

• H01F1/11 Primary

  in the form of particles {(for magnetic record carriers G11B5/70626)} · CPC title

• C04B2235/3215

  Barium oxides or oxide-forming salts thereof · CPC title

• C01G49/0036

  containing one alkaline earth metal, magnesium or lead · CPC title

• C04B2235/3284

  Zinc oxides, zincates, cadmium oxides, cadmiates, mercury oxides, mercurates or oxide forming salts thereof · CPC title

• C04B2235/3213

  Strontium oxides or oxide-forming salts thereof · CPC title