Dowa Electronics Materials Co., Ltd.

The University of Tokyo

Dowa Mining Co., Ltd.

Fujifilm Corporation

Kenji Masada

Takafumi Amino

Shin-ichi Ohkoshi

Asuka Namai

Akira Nagatomi

Kenta Imoto

Hiroshi Kimura

Norihito Kasada

Shinya Sasaki

Takayuki Yoshida

Kenichi Inoue

Toshio Tada

Toshihiko Ueyama

Hiroko Tokoro

Hirohisa Omoto

Shinichi Konno

Daisuke Abe

Syunsuke Oka

Koji Nakabayashi

Shizuka Anan

Futoshi Nagashima

Tomoyuki Ishiyama

Gousuke Iwasaki

Yuzo Ishikawa

There is provided an oriented body containing platinum group-substituted-6 iron oxide particles typified by Rh-substituted &#x3b5;-iron oxide or Ru-substituted &#x3b5;-iron oxide applicable to MAMR, MIMR, or F-MIMR system, and a technique related thereto, containing platinum group element-substituted &#x3b5;-iron oxide particles in which a part of &#x3b5;-iron oxide is substituted with at least one element of platinum group elements, as magnetic particles wherein the degree of orientation of the magnetic particles defined by the degree of orientation=SQ (direction of magnetization easy-axes)/SQ (direction of magnetization hard-axes) exceeds 5.0, and a coercive force exceeds 31 kOe.

Oriented body, method for producing the same, device for producing the same, and magnetic recording medium

An epsilon iron oxide has an average particle size of 10 to 18 nm, a part of the iron element being substituted with a substitutional element and has a coercive force of 14 kOe or less, wherein a coefficient of variation of the particle size is 40% or less. A method for producing the same, a magnetic coating material and a magnetic recording medium using the epsilon iron oxide, includes depositing a metal compound of a substitutional element on iron oxide hydroxide to thereby obtain iron oxide hydroxide on which the metal compound is deposited; coating the iron oxide hydroxide on which the metal compound is deposited, with silicon oxide to thereby obtain iron oxide hydroxide coated with the silicon oxide; and applying heat treatment to the silicon oxide-coated iron oxide hydroxide in an oxidizing atmosphere, wherein a part of an iron element is substituted with the substitutional element.

Epsilon iron oxide and method for producing the same, magnetic coating material and magnetic recording medium

There are provided an oriented body such as a magnetic sheet in which a value of degree of orientation of magnetic particles is beyond 3.5, and a method for producing the same, and a device for producing the same, wherein the oriented body such as a magnetic sheet is produced through the steps of: mixing a mixed solution containing a solvent and a vehicle and &#x3b5;-iron oxide particles by shaking stirring, and dispersing the &#x3b5;-iron oxide particles in the mixed solution; providing a mixed solution in which the &#x3b5;-iron oxide particles are dispersed, on a predetermined substrate; and removing the solvent while applying a magnetic field to the substrate provided with the mixed solution, to obtain an oriented body.

Oriented body containing  e-iron oxide, method for producing the same, and device for producing the same

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.

Magnetic powder for magnetic recording medium

A magnetic powder for magnetic recording medium comprises acicular particles constituted primarily of Fe, wherein the powder contains Co in an amount such that the Co/Fe ratio is 50 at. % or less and the Co is contained in a manner such that the surface portion has a higher concentration than the core portion of the particles, and upon subjecting the magnetic powder for magnetic recording medium to TG measurement, the powder exhibits at least two oxidation starting points: a low-temperature side oxidation starting point and a high-temperature side oxidation starting point. The magnetic powder achieves improved resistance to oxidation without sacrificing magnetic characteristics.

Method of producing magnetic powder for magnetic recording medium

A hexagonal crystal ferrite magnetic powder having high magnetic characteristics while having a small particle volume and a high specific surface area is provided, and a high-density magnetic recording medium using the powder. A method for producing a hexagonal crystal ferrite formed using a glass crystallization method includes the steps of: mixing a glass matrix with raw materials including iron, bismuth, a divalent metal (M1), a tetravalent metal (M2), any one kind (A) of barium, strontium, calcium, and lead, and at least one kind of rare earth element (represented by R) having a mole equal to or less than that of the iron; heating the mixed raw material to obtain a glass body; quenching the glass body, pulverizing the glass body, and performing a heat treatment, and washing the glass body after the heat treatment with an acid solution.

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

A method for producing a magnetic powder comprised chiefly of FeNcomprising providing a starting powder comprising an oxy-hydroxide or oxide of iron and an amount of noble metal. The starting powder is reduced into an iron powder by a dry method using a hydrogen gas; and the iron powder is nitrided into a magnetic powder comprised chiefly of FeNparticles using a nitrogen-containing gas at a temperature not higher than 200&#xb0; C. The amount of noble metal is such that an amount that the atomic percent ratio of the noble metal content to Fe in the magnetic powder is 0.01-10.

Magnetic powder suitable for low-noise media

A high-reliability iron nitride-based magnetic powder with markedly improved weatherability with respect to deterioration over time of the magnetic properties in fine particles smaller than 25 nm is formed by adhering one or more of the elements Si and P to the surface of an iron nitride-based magnetic powder constituted primarily of FeNwith an average grain size of 25 nm or less, where the total content of Si and P in the magnetic powder may be 0.1% or greater as an atomic ratio with respect to Fe. In particular, the invention provides an iron nitride-based magnetic powder such that the value &#x394;Has defined by Equation (1) below is 5% or less and the value &#x394;&#x3c3;as defined by Equation (2) below is 20% or less.&#x394;=()/100&#x2003;&#x2003;(1)&#x394;&#x3c3;=(&#x3c3;&#x2212;&#x3c3;)/&#x3c3;100&#x2003;&#x2003;(2) Here, Hand &#x3c3;are the coercivity and saturation magnetization, respectively, of the magnetic powder after being kept for one week at a constant temperature and constant humidity of 60&#xb0; C. and 90% RH. Hand &#x3c3;are the coercivity and saturation magnetization of the magnetic powder before being kept at constant temperature and constant humidity.

High-weatherability iron nitride-based magnetic powder and method of manufacturing the powder

An iron nitride magnetic powder consisting primarily of FeNphase whose average particle diameter determined by particle size measurement using a TEM micrograph is 20 nm or less and whose geometric standard deviation of the particle diameter is 1.4 or less. The iron nitride magnetic powder can be obtained by a method of producing an iron nitride magnetic powder consisting primarily of FeNphase includes a step of, at the time of producing an iron nitride magnetic powder consisting primarily of FeNphase by subjecting a reduced powder obtained by reduction of iron oxide to ammonia treatment, using goethite containing Al in solid solution as the iron oxide.

Iron nitride magnetic powder and method of producing the powder

An iron nitride system magnetic powder comprising of particles comprised primarily of Fe16N(having an average particle diameter of up to 25 nm, for example) is provided, to which one or more elements selected from Si, P and Ti is adhered. The powder has a C/Fe atomic ratio of 0.5 to 30%, preferably a (Si+P+Ti)/Fe atomic ratio of 0.1 to 10%. With &#x394;Hc defined (Hc&#xb7;Hc)/Hc&#xd7;100, the powder has a &#x394;Hc of up to 5%, and with &#x394;&#x3c3;s defined as (&#x3c3;s&#xb7;&#x3c3;s)/&#x3c3;s&#xd7;100, a &#x394;&#x3c3;s of up to 20%. The powder can provide an ignition temperature of 140&#xb0; C. or above, and a tap density of 1.0 g/cmor above. Hcand &#x3c3;sare the coercive force (kA/m) and saturation magnetization (Am/kg), respectively, of the iron nitride system magnetic powder after adhesion, and Hcand &#x3c3;sare the coercive force (kA/m) and saturation magnetization (Am/kg), respectively, of the powder after it has been stored in a thermo-hygrostat for one week at a temperature of 60&#xb0; C. and a relative humidity of 90%.

Iron nitride system magnetic powder having good storage stability

An iron nitride magnetic powder comprised primarily of FeNphase is characterized in that its coercive force Hc is 200 KA/m or greater and bulk switching field distribution BSDF is 2 or less. The magnetic powder can be produced by allowing a nitriding reaction of Fe particles with a nitrogen-containing gas for producing nitrided particles of primarily FeNphase to proceed under an increased pressure of 0.1 MPa or greater. The enhanced properties of the iron nitride magnetic powder make it suitable as a magnetic material for high-density magnetic recording media.

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Okayama, Japan

Kenji Masada