# US 10,504,548 B2 · Iron-based oxide magnetic particle powder and method for producing iron-based oxide magnetic particle powder

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- Number: US 10,504,548 B2
- Document ID: US10504548B2
- Status: Granted
- Kind: B2
- Application number: 15/511,038
- Filed: 2015-09-17
- Published: 2017-10-05
- Granted: 2019-12-10
- Earliest claimed: 2014-09-24
- Assignees: Dowa Electronics Materials Co., Ltd.
- Applicants: Dowa Electronics Materials Co., Ltd.
- Inventors: Kenji Sakane; Tetsuya Kawahito
- Web page: https://patentgrep.com/patent/US10504548B2

## CPC

- G11B 5/658: {containing oxygen, e.g. molecular oxygen or magnetic oxide}
- C01G 49/0018: {Mixed oxides or hydroxides, (C01G49/0009 takes precedence)}
- C01G 49/06: Ferric oxide [Fe2O3]
- C01G 51/40: Complex oxides containing cobalt and at least one other metal element
- G11B 5/70642: {iron oxides}
- G11B 5/714: characterised by the dimension of the magnetic particles
- H01F 1/11: in the form of particles {(for magnetic record carriers G11B5/70626)}
- B82Y 25/00: Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- B82Y 40/00: Manufacture or treatment of nanostructures
- C01P 2002/50: Solid solutions
- C01P 2002/52: containing elements as dopants
- C01P 2002/72: by d-values or two theta-values, e.g. as X-ray diagram
- C01P 2004/04: obtained by TEM, STEM, STM or AFM
- C01P 2004/51: Particles with a specific particle size distribution
- C01P 2004/64: Nanometer sized, i.e. from 1-100 nanometer
- C01P 2006/42: Magnetic properties
- Y10S 977/773: Nanoparticle, i.e. structure having three dimensions of 100 nm or less
- Y10S 977/811: Of specified metal oxide composition, e.g. conducting or semiconducting compositions such as ITO, ZnOx
- Y10S 977/896: Chemical synthesis, e.g. chemical bonding or breaking
- Y10S 977/943: Information storage or retrieval using nanostructure
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

An e-type iron-based oxide magnetic particle powder has narrow particle size distribution and has a low content of fine particles which do not contribute to magnetic recording characteristics. As a result, a narrow coercive force distribution is achieved and the powder is suitable for increasing recording density of a magnetic recording medium. The powder containing substituting metal elements can be obtained by: adding an alkali to an aqueous solution containing trivalent iron ions and ions of the metals for partially substituting Fe sites to neutralize the aqueous solution to a pH of 1.5 to 2.5; then adding a hydroxycarboxylic acid; further adding the alkali to neutralize the aqueous solution to a pH of 8.0 to 9.0; washing with water a precipitation of an iron oxyhydroxide containing the substituting metal elements produced; and coating the iron oxyhydroxide containing the substituting metal elements with a silicon oxide and heating the resultant.

## Claims

### Claim 1

An iron-based oxide magnetic particle powder in which a part of Fe sites of ε-Fe2O3 is substituted with another metal element, having a mean particle diameter as measured by a transmission electron microscopy of 10 nm to 30 nm, wherein an IL/IH value defined below is 0.7 or less:
wherein IH is the intensity of a peak appearing on the higher magnetic field side in a differential B-H curve obtained by numerically differentiating a B-H curve obtained by a measurement under conditions of an applied magnetic field of 1035 kA/m (13 kOe), an M measurement range of 0.005 A·m2 (5 emu), a step bit of 80 bit, a time constant of 0.03 sec, and a wait time of 0.1 sec, and IL is the intensity of the intercept on the vertical axis at the zero magnetic field in the differential B-H curve.

### Claim 2 (depends on 1)

The iron-based oxide magnetic particle powder according to claim 1, wherein the IL/IH value is 0.53 or less.

### Claim 3 (depends on 1)

The iron-based oxide magnetic particle powder according to claim 1, wherein the iron-based oxide is represented by ε-AxByCzFe2-x-y-zO3 (wherein, A represents at least one divalent metal element selected from Co, Ni, Mn, and Zn, B represents at least one tetravalent metal element 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 are satisfied).

### Claim 4 (depends on 1, 2)

The iron-based oxide magnetic particle powder according to claim 1 or 2, wherein the iron-based oxide is represented by ε-ByCzFe2-y-zO3 (wherein, B represents at least one tetravalent metal element selected from Ti and Sn, C represents at least one trivalent metal element selected from In, Ga, and Al, and 0<y, z<1 are satisfied).

### Claim 5 (depends on 1)

The iron-based oxide magnetic particle powder according to claim 1, wherein the iron-based oxide is represented by ε-CzFe2-zO3 (wherein, C represents at least one trivalent metal element selected from In, Ga, and Al, and 0<z<1 are satisfied).

### Claim 6 (depends on 1)

A coating material for a coating type magnetic recording medium, wherein the iron-based oxide magnetic particle powder as set forth in claim 1 is used.

### Claim 7 (depends on 1)

A magnetic recording medium, wherein the iron-based oxide magnetic particle powder as set forth in claim 1 is used.

### Claim 8

A method for producing an iron-based oxide magnetic particle powder in which a part of Fe sites of ε-Fe2O3 is substituted with another metal element, having a mean particle diameter as measured by a transmission electron microscopy of 10 nm to 30 nm, the method comprising:
a first neutralization step in which an aqueous solution containing trivalent iron ions and ions of the metal for partially substituting the Fe sites is neutralized to a pH of 1.5 to 2.5;
a step in which a hydroxycarboxylic acid is added to the aqueous solution after the neutralization;
a second neutralization step in which the aqueous solution having the hydroxycarboxylic acid added is neutralized to a pH of 8.0 to 9.0;
a step in which an iron oxyhydroxide containing the substituting metal element produced in the second neutralization step is subjected to water washing;
a step in which the iron oxyhydroxide containing the substituting metal element after the water washing is coated with a silicon oxide; and
a step in which the iron oxyhydroxide containing the substituting metal element coated with the silicon oxide is heated to produce an iron oxide containing the substituting metal element coated with the silicon oxide, wherein a value of IL/IH defined below is 0.7 or less: wherein IH is the intensity of a peak appearing on the higher magnetic field side in a differential B-H curve obtained by numerically differentiating a B-H curve obtained by a measurement under conditions of an applied magnetic field of 1035 kA/m (13 kOe), an M measurement range of 0.005 A*m2 (5 emu), a step bit of 80 bit, a time constant of 0.03 sec, and a wait time of 0.1 sec, and IL is the intensity of the intercept on the vertical axis at the zero magnetic field in the differential B-H curve.

### Claim 9 (depends on 8)

The method for producing an iron-based oxide magnetic particle powder according to claim 8, wherein the value of IL/IH is 0.53 or less.

### Claim 10 (depends on 8)

The method for producing an iron-based oxide magnetic particle powder according to claim 8, wherein the iron-based oxide is represented by ε-AxByCzFe2-x-y-zO3 (wherein, A represents at least one divalent metal element selected from Co, Ni, Mn, and Zn, B represents at least one tetravalent metal element 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 are satisfied).

### Claim 11 (depends on 8)

The method for producing an iron-based oxide magnetic particle powder according to claim 8, wherein the iron-based oxide is represented by ε-ByCzFe2-y-zO3 (wherein, B represents at least one tetravalent metal element selected from Ti and Sn, C represents at least one trivalent metal element selected from In, Ga, and Al, and 0<y, z<1 are satisfied).

### Claim 12 (depends on 8)

The method for producing an iron-based oxide magnetic particle powder according to claim 8, wherein the iron-based oxide is represented by ε-CZFe2-zO3 (wherein, C represents at least one trivalent metal element selected from In, Ga, and Al, and 0<z<1 are satisfied).

### Claim 13 (depends on 8)

The method for producing an iron-based oxide magnetic particle powder according to claim 8, wherein the hydroxycarboxylic acid is one or more of tartaric acid, citric acid, and malic acid.

### Claim 14 (depends on 8)

An iron-based oxide magnetic particle powder produced by the method for producing an iron-based oxide magnetic particle powder as set forth in claim 8.

### Claim 15

A method for producing an iron-based oxide magnetic particle powder in which a part of Fe sites of ε-Fe2O3 is substituted with another metal element, having a mean particle diameter as measured by a transmission electron microscopy of 10 nm to 30 nm, the method comprising:
a first neutralization step in which an aqueous solution containing trivalent iron ions and ions of the metal for partially substituting the Fe sites is neutralized to a pH of 1.5 to 2.5;
a step in which a hydroxycarboxylic acid is added to the aqueous solution after the neutralization;
a second neutralization step in which the aqueous solution having the hydroxycarboxylic acid added is neutralized to a pH of 8.0 to 9.0;
a step in which an iron oxyhydroxide containing the substituting metal element produced in the second neutralization step is subjected to water washing;
a step in which the iron oxyhydroxide containing the substituting metal element after the water washing is coated with a silicon oxide;
a step in which the iron oxyhydroxide containing the substituting metal element coated with the silicon oxide is heated to produce an iron oxide containing the substituting metal element coated with the silicon oxide; and
a step in which the silicon oxide coating the iron oxide containing the substituting metal element is removed, wherein a value of IL/IH defined below is 0.7 or less: wherein IH is the intensity of a peak appearing on the higher magnetic field side in a differential B-H curve obtained by numerically differentiating a B-H curve obtained by a measurement under conditions of an applied magnetic field of 1035 kA/m (13 kOe), an M measurement range of 0.005 A*m2 (5 emu), a step bit of 80 bit, a time constant of 0.03 sec, and a wait time of 0.1 sec, and IL is the intensity of the intercept on the vertical axis at the zero magnetic field in the differential B-H curve.

### Claim 16

A method for producing an iron-based oxide magnetic particle powder in which a part of Fe sites of ε-Fe2O3 is substituted with another metal element, having a mean particle diameter as measured by a transmission electron microscopy of 10 nm to 30 nm, the method comprising:
a first neutralization step in which an aqueous solution containing trivalent iron ions and ions of the metal for partially substituting the Fe sites is neutralized to a pH of 1.5 to 2.5;
a step in which a hydroxycarboxylic acid is added to the aqueous solution after the neutralization;
a second neutralization step in which the aqueous solution having the hydroxycarboxylic acid added is neutralized to a pH of 8.0 to 9.0;
a step in which an iron oxyhydroxide containing the substituting metal element produced in the second neutralization step is subjected to water washing;
a step in which the iron oxyhydroxide containing the substituting metal element after the water washing is coated with a silicon oxide;
a step in which the iron oxyhydroxide containing the substituting metal element coated with the silicon oxide is heated to produce an iron oxide containing the substituting metal element coated with the silicon oxide; and
a step in which the silicon oxide coating the iron oxide containing the substituting metal element is removed and then the iron oxide containing the substituting metal element is classified, wherein a value of IL/IH defined below is 0.7 or less: wherein IH is the intensity of a peak appearing on the higher magnetic field side in a differential B-H curve obtained by numerically differentiating a B-H curve obtained by a measurement under conditions of an applied magnetic field of 1035 kA/m (13 kOe), an M measurement range of 0.005 A*m2 (5 emu), a step bit of 80 bit, a time constant of 0.03 sec, and a wait time of 0.1 sec, and IL is the intensity of the intercept on the vertical axis at the zero magnetic field in the differential B-H curve.

### Claim 17

A method for producing an iron-based oxide magnetic particle powder in which a part of Fe sites of ε-Fe2O3 is substituted with another metal element, having a mean particle diameter as measured by a transmission electron microscopy of 10 nm to 30 nm, the method comprising:
a first neutralization step in which an aqueous solution containing trivalent iron ions and ions of the metal for partially substituting the Fe sites is neutralized to a pH of 1.5 to 2.5;
a step in which a hydroxycarboxylic acid is added to the aqueous solution after the neutralization;
a second neutralization step in which the aqueous solution having the hydroxycarboxylic acid added is neutralized to a pH of 8.0 to 9.0;
a step in which an iron oxyhydroxide containing the substituting metal element produced in the second neutralization step is subjected to water washing;
a step in which a hydrothermal treatment at 120° C. to 180° C. is applied to the iron oxyhydroxide containing the substituting metal element after the water washing;
a step in which the iron oxyhydroxide containing the substituting metal element after the hydrothermal treatment is coated with a silicon oxide;
a step in which the iron oxyhydroxide containing the substituting metal element coated with the silicon oxide is heated to produce an iron oxide containing the substituting metal element coated with the silicon oxide; and
a step in which the silicon oxide coating the iron oxide containing the substituting metal element is removed, wherein a value of IL/IH defined below is 0.7 or less: wherein IH is the intensity of a peak appearing on the higher magnetic field side in a differential B-H curve obtained by numerically differentiating a B-H curve obtained by a measurement under conditions of an applied magnetic field of 1035 kA/m (13 kOe), an M measurement range of 0.005 A*m2 (5 emu), a step bit of 80 bit, a time constant of 0.03 sec, and a wait time of 0.1 sec, and IL is the intensity of the intercept on the vertical axis at the zero magnetic field in the differential B-H curve.