Iron-based oxide magnetic particle powder, method for producing same, coating material, and magnetic recording medium

Patent metadata

Field	Value
Publication number	US-10622127-B2
Application number	US-201515541505-A
Country	US
Kind code	B2
Filing date	Dec 28, 2015
Priority date	Jan 9, 2015
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

An iron-based oxide magnetic particle powder has a narrow particle size distribution a small content of fine particles that do not contribute to magnetic recording characteristics, and a narrow coercive force distribution, to enhance magnetic recording medium density. Neutralizing an aqueous solution containing a trivalent iron ion and an ion of the metal substituting a part of the Fe sites by adding an alkali to make pH of 1.5 or more and 2.5 or less, adding a hydroxycarboxylic acid, and further neutralizing by adding an alkali to make pH of 8.0 or more and 9.0 or less are performed at 5° C. or more and 25° C. or less. A formed iron oxyhydroxide precipitate containing the substituting metal element is rinsed with water, then coated with silicon oxide, and then heated thereby providing e-type iron-based oxide magnetic particle powder. The rinsed precipitate may be subjected to a hydrothermal treatment.

First claim

The invention claimed is:

1. An iron-based oxide magnetic particle powder comprising ε-Fe 2 O 3 having an average particle diameter measured with a transmission electron microscope of 10 nm or more and 30 nm or less, a part of Fe sites of which is substituted by another metal element, the iron-based oxide magnetic particle powder having a value of I L /I H defined below of 0.7 or less and a value of α s /ε s defined below of 0.1 or less,
wherein I H represents an intensity of a peak present on a high magnetic field side in a differential B-H curve obtained by numerical differential of a B-H curve obtained by measuring under conditions of an applied magnetic field of 1,035 kA/m (13 kOe), an M measurement range of 0.005 A·m 2 (5 emu), a step bit of 80 bit, a time constant of 0.03 sec, and a wait time of 0.1 sec; and I L represents an intensity of an intercept of an ordinate at zero magnetic field in the differential B-H curve, and
α s represents a maximum value of a diffraction intensity except for background in X-ray diffractometry at 2θ of 27.2° or more and 29.7° or less; and ε s represents a maximum value of a diffraction intensity except for background in X-ray diffractometry at 2θ of 42° or more and 44° or less.

2. The iron-based oxide magnetic particle powder according to claim 1 , wherein the iron-based oxide is ε-A x B y C z Fe 2-x-y-z O 3 (wherein A represents at least one divalent metal element selected from Co, Ni, Mn, and Zn; B represents at least one tetravalent metal atom selected from Ti and Sn; C represents at least one trivalent metal element selected from In, Ga, and Al; and 0<x, y, z<1).

3. A method for producing iron-based oxide magnetic particle powder comprising ε-Fe 2 O 3 having an average particle diameter measured with a transmission electron microscope of 10 nm or more and 30 nm or less, a part of Fe sites of which is substituted by another metal element,
the method comprising:
a first neutralization step of neutralizing an aqueous solution containing a trivalent iron ion and an ion of the metal substituting a part of the Fe sites to make pH of 1.5 or more and 2.5 or less at a temperature retained at 5° C. or more and 25° C. or less;
adding a hydroxycarboxylic acid to the aqueous solution after neutralizing, at a temperature retained at 5° C. or more and 25° C. or less;
a second neutralization step of neutralizing the aqueous solution to make pH of 8.0 or more and 9.0 or less at a temperature retained at 5° C. or more and 25° C. or less after adding the hydroxycarboxylic acid;
rinsing a formed precipitate of iron oxyhydroxide containing the substituting metal element formed in the second neutralization step, with water;
coating a silicon oxide on the iron oxyhydroxide containing the substituting metal element after rinsing with water; and
heating the iron oxyhydroxide containing the substituting metal element coated with the silicon oxide to provide an iron oxide containing the substituting metal element coated with the silicon oxide.

4. The method for producing iron-based oxide magnetic particle powder according to claim 3 , wherein the method further comprises:
removing the silicon oxide coated on the iron oxide containing the substituting metal element,
after providing the iron oxide containing the substituting metal element coated with the silicon oxide.

5. The method for producing iron-based oxide magnetic particle powder according to claim 3 , wherein the iron-based oxide magnetic particle powder has a value of I L /I H defined below of 0.7 or less and a value of α s /ε s defined below of 0.1 or less,
wherein I H represents an intensity of a peak present on a high magnetic field side in a differential B-H curve obtained by numerical differential of a B-H curve obtained by measuring under conditions of an applied magnetic field of 1,035 kA/m (13 kOe), an M measurement range of 0.005 A·m 2 (5 emu), a step bit of 80 bit, a time constant of 0.03 sec, and a wait time of 0.1 sec; and I L represents an intensity of an intercept of an ordinate at zero magnetic field in the differential B-H curve, and
α s represents a maximum value of a diffraction intensity except for background in X-ray diffractometry at 2θ of 27.2° or more and 29.7° or less; and ε s represents a maximum value of a diffraction intensity except for background in X-ray diffractometry at 2θ of 42° or more and 44° or less.

6. The method for producing iron-based oxide magnetic particle powder according to claim 3 , wherein the iron-based oxide is ε-A x B y C z Fe 2-x-y-z O 3 (wherein A represents at least one divalent metal element selected from Co, Ni, Mn, and Zn; B represents at least one tetravalent metal atom selected from Ti and Sn; C represents at least one trivalent metal element selected from In, Ga, and Al; and 0<x, y, z<1).

7. The method for producing iron-based oxide magnetic particle powder according to claim 3 , wherein the hydroxycarboxylic acid is at least one selected from tartaric acid, citric acid, and malic acid.

8. A method for producing iron-based oxide magnetic particle powder comprising ε-Fe 2 O 3 having an average particle diameter measured with a transmission electron microscope of 10 nm or more and 30 nm or less, a part of Fe sites of which is substituted by another metal element,
the method comprising:
a first neutralization step of neutralizing an aqueous solution containing a trivalent iron ion and an ion of the metal substituting a part of the Fe sites to make pH of 1.5 or more and 2.5 or less at a temperature retained at 5° C. or more and 25° C. or less;
adding a hydroxycarboxylic acid to the aqueous solution after neutralizing, at a temperature retained at 5° C. or more and 25° C. or less;
a second neutralization step of neutralizing the aqueous solution to make pH of 8.0 or more and 9.0 or less at a temperature retained at 5° C. or more and 25° C. or less after adding the hydroxycarboxylic acid;
rinsing a formed precipitate of iron oxyhydroxide containing the substituting metal element formed in the second neutralization step, with water;
subjecting the iron oxyhydroxide containing the substituting metal element after rinsing with water, to a hydrothermal treatment at 120° C. or more and 180° C. or less;
coating a silicon oxide on the iron oxyhydroxide containing the substituting metal element after subjecting to the hydrothermal treatment; and
heating the iron oxyhydroxide containing the substituting metal element coated with the silicon oxide to provide an iron oxide containing the substituting metal element coated with the silicon oxide.

9. The method for producing iron-based oxide magnetic particle powder according to claim 8 , wherein the method further comprises:
removing the silicon oxide coated on the iron oxide containing the substituting metal element,
after providing the iron oxide containing the substituting metal element coated with the silicon oxide.

10. Iron-based oxide magnetic particle powder produced by the method for producing iron-based oxide magnetic particle powder according to claim 3 .

11. A coating material for a coating type magnetic recording medium, comprising the iron-based oxide magnetic particle powder according to claim 1 .

12. A magnetic recording medium comprising the iron-based oxide magnetic particle powder according to claim 1 .

Assignees

• Dowa Electronics Materials Co Ltd

Inventors

• Sakane Kenji
• Kawahito Tetsuya

Classifications

• G11B5/842

  Coating a support with a liquid magnetic dispersion · CPC title

• H01F1/0054

  Coated nanoparticles, e.g. nanoparticles coated with organic surfactant · CPC title

• H01F1/0315 Primary

  Ferrites · CPC title

• C01G49/06

  Ferric oxide [Fe2O3] · CPC title

• H01F1/14725

  with insulating coating · CPC title