Magnetic powder for magnetic recording medium, and production method thereof
US-2020161035-A1 · May 21, 2020 · US
Hexagonal ferrite magnetic powder
US11404190B2 · US · B2
| Field | Value |
|---|---|
| Publication number | US-11404190-B2 |
| Application number | US-201916702629-A |
| Country | US |
| Kind code | B2 |
| Filing date | Dec 4, 2019 |
| Priority date | Dec 6, 2018 |
| Publication date | Aug 2, 2022 |
| Grant date | Aug 2, 2022 |
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Abstract
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Provided is a hexagonal ferrite magnetic powder for a magnetic recording medium, containing hexagonal ferrite magnetic particles having aluminum hydroxide adhered on the surface thereof, the hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, a Co/Fe molar ratio of 0.002 to 0.030, and a Nb/Fe molar ratio of 0.005 to 0.050, and having an Fe site valence AFe of 3.015 to 3.040 as calculated by AFe=(3+2×[Co/Fe]+5×[Nb/Fe])/(1+[Co/Fe]+[Nb/Fe]) wherein [Co/Fe] represents the Co/Fe molar ratio and [Nb/Fe] represents the Nb/Fe molar ratio, and preferably having an activation volume Vact of 1400 to 1800 nm3. This magnetic powder simultaneously achieves an increase in magnetic characteristics including SNR of a magnetic recording medium and a further increase in durability thereof.
First claim
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What is claimed is: 1. A hexagonal ferrite magnetic powder for a magnetic recording medium, comprising hexagonal ferrite magnetic particles having aluminum hydroxide adhered on the surface thereof, the hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, a Co/Fe molar ratio of 0.002 to 0.030, and a Nb/Fe molar ratio of 0.005 to 0.050, and having an Fe site valence A Fe of 3.015 to 3.040 as calculated by the following formula (1), wherein a generalized Fe site valence X Fe as calculated by the following formula (2) is equal to A Fe : A Fe =(3+2×[Co/Fe]+5×[Nb/Fe])/(1+[Co/Fe]+[Nb/Fe]) (1) X Fe =(3+2×[M2/Fe]+4×[M4/Fe]+5×[M5/Fe])/(1+[M2/Fe]+[M4/Fe]+[M5/Fe]) (2) wherein [Co/Fe] represents a Co/Fe molar ratio, [Nb/Fe] represents a Nb/Fe molar ratio, [M2/Fe] represents a molar ratio of the divalent transition metals M2's to Fe, [M4/Fe] represents a molar ratio of the tetravalent transition metals M4's to Fe, and [M5/Fe] represents a molar ratio of the pentavalent transition metals M5's to Fe. 2. The hexagonal ferrite magnetic powder for a magnetic recording medium according to claim 1 , wherein the hexagonal ferrite magnetic powder has an activation volume Vact of 1400 to 1800 nm 3 . 3. A hexagonal ferrite magnetic powder for a magnetic recording medium, comprising hexagonal ferrite magnetic particles having aluminum hydroxide adhered on the surface thereof, the hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, a Co/Fe molar ratio of 0.002 to 0.030, and a Nb/Fe molar ratio of 0.005 to 0.050, and having an Fe site valence A Fe of 3.015 to 3.040 as calculated by the following formula (1), wherein substituting elements of Fe sites consist of Co and Nb: A Fe =(3+2×[Co/Fe]+5×[Nb/Fe])/(1+[Co/Fe]+[Nb/Fe]) (1) wherein [Co/Fe] represents a Co/Fe molar ratio and [Nb/Fe] represents a Nb/Fe molar ratio.
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Classifications
- G11B5/70678Primary
Ferrites · CPC title
in the form of particles {(for magnetic record carriers G11B5/70626)} · CPC title
- H01F1/344Primary
Ferrites, e.g. having a cubic spinel structure (X2+O)(Y23+O3), e.g. magnetite Fe3O4 · CPC title
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- What does patent US11404190B2 cover?
- Provided is a hexagonal ferrite magnetic powder for a magnetic recording medium, containing hexagonal ferrite magnetic particles having aluminum hydroxide adhered on the surface thereof, the hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, a Co/Fe molar ratio of 0.002 to 0.030, and a Nb/Fe molar ratio of 0.005 to 0.050, and having an Fe site valence AFe of 3.015 …
- Who is the assignee on this patent?
- Dowa Electronics Materials Co Ltd, Fujifilm Corp
- What technology area does this patent fall under?
- Primary CPC classification G11B5/70678. Mapped technology areas include Physics.
- When was this patent published?
- Publication date Tue Aug 02 2022 00:00:00 GMT+0000 (Coordinated Universal Time) (B2). Legal status and post-grant events are not shown on this page.
- What related patents are in patentsdb?
- We list 2 related publications on this page (citations in our corpus or others sharing the same primary CPC).