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Patent EP0141558A1 successfully refreshed from Google Patents.
EP0141558A1
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Process of manufacture for barium ferrite particles for magnetic recording media
Assignee: Toda Kogyo Corp
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Filing: 1984-10-12
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Granted: —
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Expires: 2004-10-12
Abstract
Abstract Hexagonal plate-like barium ferrite particles, suitable for use as the magnetic material of magnetic recording media, are represented by the formula BaFe 12-x-y M x Ti y O 19 wherein x and y are independently 0.6 to 1.2 and M is Co(II) or Co(II) and a divalent metal other than Co, the particles having a width of 0.1 to 0.4 micrometer, a BET specific surface area (S) of 20 to 50 m 2 /g, a magnetization (M) of larger than 40 emu/g in a magnetic field of 7.96 x 10 5 Am -1 (10 KOe) and a coercive force (He) of 3.98 x 10 4 Am -1 (500 to 1000 Oe).
Inventors
- 👤 Norimichi Nagai
- 👤 Nanao Horiishi
- 👤 Masao Kiyama
- 👤 Toshio Takada
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 13:23
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/714; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; G11B5/84
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
115 words
Hexagonal plate-like barium ferrite particles, suitable for use in magnetic recording, represented by the formula BaFe 12-x-y M x Ti y O 19 wherein x and y are independently from 0.6 to 1.2 and M is Co(II) or Co(II) and a divalent metal other than Co, the particles having a width of from 0.1 to 0.4 micrometer, a BET specific surface area (S) of from 20 to 50 m 2 jg, a magnetization (M) of larger than 40 emu/g in a magnetic field of 7.96 x 10 5 Am -1 (10 KOe) and a coercive force (Hc) of from 3.98 x 10 4 to 7.96 x 10 4 Am -1 (500 to 1000 O e).
Claim 2
Dependent Claim
115 words
Hexagonal plate-like barium ferrite particles, suitable for use in magnetic recording, represented by the formula BaFe 12-x-y M x Ti y O 19 wherein x and y are independently from 0.6 to 1.2 and M is Co(II) or Co(II) and a divalent metal other than Co, the particles having a width of from 0.1 to 0.4 micrometer, a BET specific surface area (S) of from 20 to 50 m 2 jg, a magnetization (M) of larger than 40 emu/g in a magnetic field of 7.96 x 10 5 Am -1 (10 KOe) and a coercive force (Hc) of from 3.98 x 10 4 to 7.96 x 10 4 Am -1 (500 to 1000 O e).
Claim 3
Dependent Claim
19 words
Particles according to claim 1, wherein M is Co(II) and a divalent metal selected from Fe(II), Zn(II) and Mn(II).
Claim 4
Dependent Claim
19 words
Particles according to claim 1 or 2, having a BET specific surface area of from 30 to 45 m2/g.
Claim 5
Dependent Claim
21 words
Particles according to any one of the preceding claims, wherein the width of each particle is from 0.1 to 0.3 micrometer.
Claim 6
Dependent Claim
32 words
Particles according to any one of the preceding claims, having a coercive force of from 4.77 x 10 to 7 . 16 x 10 4 Am -1 (600 to 900 O e).
Claim 7
Dependent Claim
13 words
Particles according to any one of the preceding claims, wherein x = y.
Claim 8
Dependent Claim
132 words
A process for producing hexagonal plate-like barium ferrite particles suitable for use in magnetic recording, represented by the formula: BaFe 12-x-y M x Ti y O 19 wherein x and y are independently from 0.6 to 1.2 and M is Co(II) or Co(II) and a divalent metal other than Co, which process comprises autoclaving at a temperature of from 250 to 330°C an aqueous alkaline suspension containing Fe(III), Ti(IV), Ba(II) and, as M(II), Co(II) or Co(II) and a divalent metal other than Co(II) and a molar excess with respect to the total amount of Fe(III), Ti(IV), Ba(II) and M(II) of an alkali metal hydroxide, treating. the thus obtained particles with an aqueous solution containing Si(IV), and subjecting the thus treated particles to thermal treatment at a temperature of not more than 900°C.
Claim 9
Dependent Claim
132 words
A process for producing hexagonal plate-like barium ferrite particles suitable for use in magnetic recording, represented by the formula: BaFe 12-x-y M x Ti y O 19 wherein x and y are independently from 0.6 to 1.2 and M is Co(II) or Co(II) and a divalent metal other than Co, which process comprises autoclaving at a temperature of from 250 to 330°C an aqueous alkaline suspension containing Fe(III), Ti(IV), Ba(II) and, as M(II), Co(II) or Co(II) and a divalent metal other than Co(II) and a molar excess with respect to the total amount of Fe(III), Ti(IV), Ba(II) and M(II) of an alkali metal hydroxide, treating. the thus obtained particles with an aqueous solution containing Si(IV), and subjecting the thus treated particles to thermal treatment at a temperature of not more than 900°C.
Claim 10
Dependent Claim
32 words
A process according to claim 7, wherein in the aqueous alkaline suspension the atomic ratio of total amount of M(II) and Ti(IV) to Fe(III) is 0.11 : 1 to 0.25 : 1.
Claim 11
Dependent Claim
20 words
A process according to claim 7 or 8, wherein the divalent metal other than Co is Fe(II), Zn(II) or Mn(II).
Claim 12
Dependent Claim
30 words
A process according to any one of claims 7 to 9, wherein the source of Fe(III) for the said aqueous alkaline suspension is ferric chloride, ferric nitrate or powdery ferricoxyhydroxide.
Claim 13
Dependent Claim
25 words
A process according to any one of claims 7 to 10, wherein the source of the Ba(II) is barium hydroxide, barium nitrate or barium chloride.
Claim 14
Dependent Claim
23 words
A process according to any one of claims 7 to 11, wherein the source of the Co(II) is cobalt nitrate or cobalt chloride.
Claim 15
Dependent Claim
24 words
A process according to any one of claims 7 to 12, wherein the source of the Ti(IV) is titanium chloride or an alkali titanate.
Claim 16
Dependent Claim
23 words
A process according to any one of claims 7 to 13, wherein the molar amount of M(II) equals the molar amount of Ti(II).
Claim 17
Dependent Claim
43 words
A magnetic recording medium in which the magnetic material comprises hexagonal plate-like barium ferrite particles as claimed in any one of claims 1 to 6 or which have been prepared by a process as claimed in any one of claims 7 to 14.
References Cited (Backward Citations)
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