Dowa Electronics Materials Co., Ltd.

Fujifilm Corporation

The University of Arizona

Materials Co., Ltd.

Hirohisa Omoto

Toshio Tada

Hiroyuki Suzuki

Shuji Kaneda

Norihito Kasada

Takayuki Kikuchi

Takayuki Yoshida

Toshihiko Ueyama

Kenji Masada

Satoshi Shiki

Daisuke Abe

Akifumi Onodera

Futoshi Nagashima

Dong Chul Pyun

Heemin Yoo

Masaki Koshiko

A hexagonal ferrite magnetic powder is significantly more useful for achieving simultaneously both the enhancement of the recording density and the enhancement of the SNR of a magnetic recording medium. The hexagonal ferrite magnetic powder contains Bi at a Bi/Fe molar ratio in a range of 0.035 or less, has a saturation magnetization σs of 42.0 Am/kg or more and a Dx volume calculated based on the crystallite diameters of 1,800 nmor less. A method for producing hexagonal ferrite magnetic powder includes a step of performing a treatment of immersing hexagonal ferrite magnetic powder containing Bi in a solution having dissolved therein a compound X that forms a complex with Bi, so as to elute a part of Bi existing in the hexagonal ferrite magnetic powder into the solution.

Hexagonal ferrite magnetic powder and method for producing same

Provided is an Al-containing hexagonal ferrite magnetic powder which produces an excellent durability-improving effect on a magnetic recording medium, wherein uniform pulverization of the magnetic powder can be easily achieved by dispersion treatment in preparation of a magnetic coating material even in cases where the magnetic powder has a small primary particle size or has a composition which is likely to produce hard secondary particles. The magnetic powder for a magnetic recording medium is an Al-containing hexagonal ferrite magnetic powder having an Al/Fe molar ratio of 0.030 to 0.200, and has a particle size distribution in which the volume ratio of particles having a particle size of 30 μm or more as measured by a laser diffraction particle size distribution analyzer with a dispersion pressure of 100 kPa is 5.0% or less, and an activation volume Vact of 1800 nmor less.

Magnetic powder for magnetic recording medium

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 Aof 3.015 to 3.040 as calculated by A=(3+2&#xd7;[Co/Fe]+5&#xd7;[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 nm. This magnetic powder simultaneously achieves an increase in magnetic characteristics including SNR of a magnetic recording medium and a further increase in durability thereof.

Hexagonal ferrite magnetic powder

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 nm. 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.

A metal magnetic powder having a metal magnetic phase mainly composed of ferromagnetic elements, and composed of particles containing one or more kinds of elements selected from rare earth elements including Y, and Al, Si. And the method for producing the metal magnetic powder, including the steps of: eluting the non-magnetic components in the particles under an action of a reducing agent acting on the metal magnetic powder, in a solution containing a complexing agent capable of forming the complex with the non-magnetic components; and forming an oxide layer on the particles in the solution after eluting the non-magnetic components into the solution, without drying the particles.

Metal magnetic powder and process for producing the same, magnetic coating material, and magnetic recording medium

A metallic magnetic powder where a primary particle of each metallic magnetic particle is a powder without forming an aggregate, and a method of making the same that includes manufacturing a metallic magnetic powder constituted of metallic magnetic particles, containing a metallic magnetic phase, with Fe, or Fe and Co as main components, rare earth elements, or yttrium and one or more non-magnetic components removing the non-magnetic component from the metallic magnetic with a reducing agent, while making a complexing agent exist for forming a complex with the non-magnetic component in water; oxidizing the metallic magnetic particle with the non-magnetic component removed; substituting water adhered to the oxidized metallic magnetic particle with an organic solvent; and coating the surface of the metallic magnetic particle with an organic matter different from the organic solvent, while maintaining a wet condition of the metallic magnetic particle with the organic solvent adhered thereto.

Metallic magnetic powder and manufacturing method of the same, magnetic painting, magnetic powder for magnetic therapy, and magnetic recording medium

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Tokyo, Japan

Hirohisa Omoto