MAGNETIC POWDER FOR MAGNETIC RECORDING MEDIUM

• US 20150123026A1
• Filed: 10/31/2014
• Published: 05/07/2015
• Est. Priority Date: 11/01/2013
• Status: Active Grant

• Current Assignee: Dowa Electronics Materials Co. Ltd. (DOWA Holdings Company Limited), Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Dowa Electronics Materials Co. Ltd. (DOWA Holdings Company Limited), Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: OMOTO, Hirohisa, TADA, Toshio, MASADA, Kenji, NAGASHIMA, Futoshi, ABE, Daisuke, KASADA, Norihito
• Granted Patent: US 9,741,479 B2
• Time in Patent Office: Days
• US Class Current: 252/62.63
• CPC Class Codes: C01G 49/0036 containing one alkaline earth metal, magnesium or lead
• CPC Class Codes: C01P 2002/76 by a space-group or by other symmetry indications
• CPC Class Codes: C01P 2006/42 Magnetic properties
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: H01F 1/11 in the form of particles for magnetic record carriers G11B5/70626

Abstract

Provided is magnetic powder capable of enhancing simultaneously both magnetic characteristics including SNP and durability of a magnetic recording medium. The hexagonal ferrite magnetic powder for a magnetic recording medium has a Ba/Fe molar ratio of 8.0% or more, a Bi/Fe molar ratio of 2.5% or more and an Al/Fe molar ratio of from 3.0 to 6.0%. The magnetic powder preferably has an activation volume Vact of from 1,400 to 1,800 nm³. The magnetic powder particularly preferably has a coercive force Hc of from 159 to 279 kA/m (which is approximately from 2,000 to 3,500 Oe) and a coercivity distribution SFD of from 0.3 to 1.0. The magnetic powder may contain, as an element that substitutes an Fe site of the hexagonal ferrite, at least one kind selected from divalent transition metals M1 and tetravalent transition metals M2.

Claims

1. Hexagonal ferrite magnetic powder for a magnetic recording medium, having a Ba/Fe molar ratio of 8.0% or more, a Bi/Fe molar ratio of 2.5% or more and an Al/Fe molar ratio of from 3.0 to 6.0%.

2. The hexagonal ferrite magnetic powder according to claim 1, wherein the hexagonal ferrite magnetic powder has an activation volume Vact of from 1,400 to 1,800 nm³.

3. The hexagonal ferrite magnetic powder according to claim 1, wherein the hexagonal ferrite magnetic powder has a coercive force Hc of from 159 to 279 kA/m and a coercivity distribution SFD of from 0.3 to 1.0.

4. The hexagonal ferrite magnetic powder according to claim 1, wherein the hexagonal ferrite magnetic powder contains, as an element that substitutes an Fe site of the hexagonal ferrite, at least one kind selected from divalent transition metals and tetravalent transition metals.