Spinel-type ferrimagnetic particles process for producing the same, and magnetic recording medium using the same

a technology magnetic recording media, which is applied in the field of spinel-type ferrimagnetic particles, spinel-type ferrimagnetic particles production process, and magnetic recording media using the same, can solve the problems of unsatisfactory magnetic recording media using conventional spinel-type ferrimagnetic particles, and achieve excellent chemical stability, excellent coercive force, and excellent dispersion

Inactive Publication Date: 2006-08-24
MEIJI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007] The present invention has been conducted for solving the above conventional problems. A first object of the present invention is to provide spinel-type ferrimagnetic particles exhibiting not only a high coercive force irrespective of fine particles, but also excellent dispersibility and chemical stability.
[0009] As a result of the present inventors' earnest studies, it has been found that the spinel-type ferrimagnetic particles comprising iron and a divalent metal, which contain a superparamagnetic component in a specific amount, are coated on the surface thereof with a specific hydroxide, and have an average particle diameter of not more than 30 nm, can exhibit not only a high coercive force irrespective of fine particles, but also excellent dispersibility and chemical stability. The present invention has been attained on the basis of the above finding.

Problems solved by technology

However, the magnetic recording media using these conventional spinel-type ferrimagnetic particles are still unsatisfactory as magnetic recording media for high-density recording which are required to exhibit not only a high reliability but also an improved weather resistance.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0095] Ferric chloride hexahydrate, cobalt chloride hexahydrate, nickel chloride hexahydrate and manganese chloride tetrahydrate as metal salts were respectively dissolved in pure water in a 10 L resin beaker, thereby preparing 10 L of each of an aqueous solution containing 0.225 mol / L of Fe3+, an aqueous solution containing 0.10 mol / L of Co2+, an aqueous solution containing 0.08 mol / L of Ni2+ and an aqueous solution containing 0.02 mol / L of Mn2+. Then, a 20 L resin container equipped with a stirrer and a thermometer was charged with 4 L of the Fe3+-containing aqueous solution, 2 L of the Co2+-containing aqueous solution, 2 L of the Ni2+-containing aqueous solution and 2 L of the Mn2+-containing aqueous solution to prepare 10 L of a mixed aqueous solution having a molar ratio (Fe / Co+Ni+Mn) of 2.25. The thus obtained mixed aqueous solution was heated to 50° C. while fully stirring (solution A). Next, 7.2 L of a 1.0 mol / L sodium hydroxide aqueous solution (solution B) was charged into...

examples 2 to 7

, Comparative Example 1 and Reference Examples 1 and 2

[0111] The same procedure as defined in Example 1 was conducted except that the production conditions of the spinel-type ferrimagnetic particles were variously changed, thereby obtaining spinel-type ferrimagnetic particles. The essential production conditions are shown in Tables 4 to 9; properties of the obtained co-precipitated particles are shown in Table 10; properties of the acid-etched spinel-type ferrimagnetic particles are shown in Table 11; properties of the finally obtained spinel-type ferrimagnetic particles are shown in Tables 12 to 13; and properties of the magnetic coating film produced using the spinel-type ferrimagnetic particles are shown in Table 14. Meanwhile, as a result of Moessbauer spectrum measurements of the spinel-type ferrimagnetic particles obtained in Examples 2 to 7, it was confirmed that any of the particles contained substantially no superparamagnetic component (not more than 1% by mass).

TABLE 4Ex...

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Abstract

Spinel-type ferrimagnetic particles having a composition represented by the formula: (MO).n / 2(Fe2O3) wherein M is a divalent metal; and n is a molar ratio of Fe to M (n=Fe / M) which is from more than 2.05 to less than 2.5 (2.05<n<2.5), containing a superparamagnetic component in an amount of not more than 2% by mass, and having an average particle diameter of 5 to 30 nm, said spinel-type ferrimagnetic particles being respectively coated on surface thereof with a hydroxide of at least one metal selected from the group consisting of Si, Al, P and Zn in an amount of not more than 10% by mass, calculated as the metal, as well as a magnetic recording medium containing the spinel-type ferrimagnetic particles. The spinel-type ferrimagnetic particles can exhibit a high coercive force irrespective of fine particles, and are excellent in dispersibility and chemical stability, as well as the magnetic recording medium for high-density recording can exhibit not only excellent frequency characteristics and high output characteristics, but also an excellent weather resistance and a high reliability.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to spinel-type ferrimagnetic particles, a process for producing the spinel-type ferrimagnetic particles, and a magnetic recording medium using the spinel-type ferrimagnetic particles. More particularly, the present invention relates to spinel-type ferrimagnetic particles which can exhibit a high coercive force irrespective of fine particles, especially fine particles having an average particle size of 5 to 30 nm, and are excellent in chemical stability and dispersibility; a process for producing the spinel-type ferrimagnetic particles; and a magnetic recording medium using the spinel-type ferrimagnetic particles. [0003] 2. Prior Arts [0004] With recent demands for high performance and high-density recording of magnetic recording media such as magnetic tapes, there have been used such magnetic recording media having a high coercive force (Hc), i.e., exhibiting excellent magnetic properti...

Claims

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Application Information

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IPC IPC(8): G11B5/708H01F1/00
CPCB82Y30/00C01G49/0018C01G53/006C01P2002/32C01P2006/42C04B35/265C04B35/626C04B35/62605C04B35/62805C04B35/62807C04B35/62813C04B35/62881C04B35/63C04B2235/02C04B2235/3201C04B2235/3262C04B2235/3274C04B2235/3275C04B2235/3279C04B2235/3284C04B2235/444C04B2235/5409C04B2235/5454C04B2235/549C04B2235/72C04B2235/763G11B5/70668H01F1/112H01F1/113C01P2004/64C01P2006/12
Inventor YAMAMOTO, HIROSHIKATAMOTO, TSUTOMU
Owner MEIJI UNIV
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