Magnetic powder suitable for low-noise media

a magnetic powder and low-noise technology, applied in the field of iron system magnetic powder, can solve the problems of powder susceptible to sintering during the reduction stage, difficult to record, and more and more difficult to continue to exist as independent particles, and achieve strong prevention of sintering and high c/n.

Inactive Publication Date: 2007-02-22
DOWA ELECTRONICS MATERIALS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0012] This invention was accomplished in the light of these circumstances and is directed to achieving strong prevention of sintering during reduction without causing the aforesaid problems

Problems solved by technology

However, unless the particle size of the magnetic powder is much smaller than the length of the region for recording the short-wavelength signal, a distinct magnetic transition cannot be produced, which, in practical terms, makes recording impossible.
However, as the particles get smaller, it becomes more and more difficult for the particles to continue to exist as independent particles.
For example, in the case of the metal magnetic powder generally used in a data storage tape, extreme refinement of the particle size makes the powder susceptible to sintering during the reduction stage of the production process.
Sintering increases the average particle volume, which is undesirable because the larger sintered particles become a source of noise, and also degrades the magnetic properties of the powder by deforming the particle shape.
In addition, when the powder is used to produce magnetic tape, the enlarged particles degrade dispersibility and cause loss of surface smoothness.
The magnetic powder therefore becomes unsuitable for use in high recording density media.
Although this makes output less of a concern when using a magnetic powder of low magnetization σs, it aggravates the problem of noise, because when a high-sensitivity head is used even slight noise is detected as large noise to markedly degrade the C/N ratio.
However, efforts made to reduce particle size at the starting powder stage are frequently outweighed by the effe

Method used

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  • Magnetic powder suitable for low-noise media

Examples

Experimental program
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Effect test

example 1

[0047] To 4 L (four liters) of a 0.2 mol / L aqueous solution of FeSO4 were added 0.5 L of a 12 mole / L aqueous solution of NaOH and an amount of ruthenium chloride to make Ru / Fe=0.1 at. %. The liquid mixture was maintained at a temperature of 40° C. while pure oxygen was blown into it at an average flow rate of 50 mL / min) on a period of 2.5 hours, thereby precipitating iron oxy-hydroxide (goethite) containing Ru in solid solution. Upon completion of this oxidation treatment, the precipitate (iron oxy-hydroxide) was filtered off, washed with water and then dispersed in water.

[0048] The dispersion was added with an amount of yttrium nitrate to make Y / Fe=1.0 at. % and then, at 40° C., with an amount of sodium aluminate to make Al / Fe=18.3 at. %, and with NaOH to adjust the pH to 7-8, thereby adhering yttrium and aluminum to the particle surfaces. The solid component was separated from the liquid by filtering, washed with water and dried in air at 110° C.

[0049] The so-obtained powder con...

example 2

[0051] Example 1 was repeated except that the amount of Ru added as a noble metal was changed to 0.5 at. %. The obtained powder was found by composition analysis to contain Al, Y and Ru at the rates of Al / Fe=17.9 at. %, Y / Fe=1.0 at. % and Ru / Fe=0.4 at. %. The properties of this mainly Fe16N2 magnetic powder are shown in Table 1.

example 3

[0052] Example 1 was repeated except that the amount of Ru added as a noble metal was changed to 1.0 at. % and the Ru was not incorporated in solid solution but as adhered to the particle surfaces. That is, Ru was not entrained in the iron oxy-hydroxide production reaction during synthesis of iron oxy-hydroxide by the wet method used in Example 1. Instead, ruthenium chloride was added to the liquid in which the synthesized iron oxy-hydroxide was dispersed, in an amount to make Ru / Fe=1.0 at. %. Ru was adhered to the iron oxy-hydroxide particles by the method of neutralization with NaOH, and then subjected to reduction treatment as the starting powder.

[0053] The obtained powder was found by composition analysis to contain Al, Y and Ru at the rates of Al / Fe=16.7 at. %, Y / Fe=1.0 at. % and Ru / Fe=0.8 at. %. The properties of this mainly Fe16N2 magnetic powder are shown in Table 1.

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Abstract

An iron system magnetic powder, and particularly an iron system magnetic powder comprised chiefly of Fe16N2, is provided that has an atomic ratio of total noble metal content to Fe of 0.01-10%. The magnetic powder can be produced by subjecting iron oxy-hydroxide or iron oxide having an atomic ratio of total noble metal content to Fe of 0.01-10% to reduction treatment. The average particle volume of the magnetic powder is preferably 4,000 nm3 or less. The magnetic powder is suitable for fabricating high recording density media of low noise, high output and high C/N ratio that are suitable for use with a GMR head or the like.

Description

FIELD OF THE INVENTION [0001] This invention relates to an iron system magnetic powder for use in high recording density magnetic recording media, particularly to a magnetic powder composed of fine particles that enables production of magnetic recording tape exhibiting outstanding low-noise and high C / N (carrier-to noise) properties. BACKGROUND ART [0002] In order to achieve the increasingly higher recording densities required by today's magnetic recording media, recording wavelengths are being shortened. However, unless the particle size of the magnetic powder is much smaller than the length of the region for recording the short-wavelength signal, a distinct magnetic transition cannot be produced, which, in practical terms, makes recording impossible. Thus, the particles of the magnetic powder have to be sufficiently smaller than the recording wavelength. [0003] Achieving higher recording density also requires increasing the resolving power of the recording signal, so it is also im...

Claims

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Application Information

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IPC IPC(8): G11B5/708H01F1/20
CPCG11B5/70615G11B5/70626G11B5/714H01F1/065
Inventor MASADA, KENJIISHIKAWA, YUZOKIMURA, HIROSHI
Owner DOWA ELECTRONICS MATERIALS CO LTD
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