Hexagonal ferrite magnetic powder, method for producing the same and magnetic recording medium

a technology of ferrite magnetic powder and hexagonal ferrite, which is applied in the direction of magnetic materials for record carriers, magnetic bodies, instruments, etc., can solve the problems of reducing the reproduction output, unable to achieve noise reduction without reducing s, and insufficient induction-type magnetic heads for use in the presently required reproduction of high-density records, etc., to achieve the effect of optimizing the packing ratio of the dispersion medium, high specific gravity

Inactive Publication Date: 2006-03-09
FUJIFILM HLDG CORP +1
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The invention provides a hexagonal ferrite magnetic powder that can be used in high-density magnetic recording. This powder has a specific size and magnetic properties that can reduce noise while maintaining a high coercive force. The invention also includes a method for producing the hexagonal ferrite magnetic powder and a magnetic recording medium containing it. The technical effect of this invention is to improve the performance of magnetic recording devices.

Problems solved by technology

However, the induction type magnetic head is becoming insufficient for use in the presently required reproduction of high-density records.
That is, when the number of coil turns of a reproduction head is increased in order to obtain a larger reproduction output, there results an increased inductance and an increase in resistance in high frequency region, leading to a problem of reduction in reproduction output.
However, the above-mentioned related art fails to achieve noise reduction without reducing σs and fails to provide a magnetic recording medium for high-density recording currently required.
However, reduction of σs of the magnetic powder causes reduction of output.
However, since the thickness of the magnetic layer is rendered small and σs of the magnetic powder is reduced, the output becomes smaller, thus sufficient performance not being obtained.
In addition, low noise and high output are required for a magnetic recording medium upon conducting high-density recording.

Method used

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  • Hexagonal ferrite magnetic powder, method for producing the same and magnetic recording medium
  • Hexagonal ferrite magnetic powder, method for producing the same and magnetic recording medium

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[0098] The invention is described in more detail below by reference to Examples and Comparative Examples which, however, do not limit the invention.

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Abstract

A hexagonal ferrite magnetic powder having an average tabular diameter of from 15 to 30 nm, a coercive force (Hc) of from 2,000 to 5,000 Oe (from 160 to 400 kA / m) and a saturated magnetization (σs) of equal to or more than [the average tabular diameter (nm)×0.37+45] A·m2 / kg. This magnetic powder is obtained by melting a starting material containing a material which has a composition within the hatched region (1) in the triangular phase diagram shown in FIG. 1 and quenching the molten product to obtain an amorphous product, subjecting the amorphous product to a thermal treatment, acid treatment, and washing. Also, a magnetic recording medium is obtained by adding this magnetic powder to the magnetic layer and coating it on the support.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a hexagonal ferrite magnetic powder, a method for producing the same and a magnetic recording medium. More particularly, it relates to a hexagonal ferrite magnetic powder which enables one to reduce noise without reducing σs and which is adapted for a magnetic recording medium for high-density recording reproducible by a highly sensitive head such as an MR head or a GMR head. Also, the invention relates to a magnetic recording medium containing the hexagonal ferrite magnetic powder in the magnetic layer. [0003] 2. Description of the Related Art [0004] In the field of magnetic recording, a magnetic head based on the principle of electromagnetic induction (induction type magnetic head) has been used and spread. However, the induction type magnetic head is becoming insufficient for use in the presently required reproduction of high-density records. That is, when the number of coil turns...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): G11B5/708H01F1/00C04B35/26C01G1/00G11B5/706G11B5/714
CPCG11B5/70678Y10T428/2982G11B5/714
InventorYAMAZAKI, NOBUOTAKAHASHI, MASATOSHIMANABE, AKIRASUZUKI, HIROYUKI
OwnerFUJIFILM HLDG CORP