Toda Kogyo Corporation

Imation Corporation

Hirofumi Kawasaki

Kenji Okinaka

Yasutaka Ota

Kohji Mori

Akio Mishima

Norimichi Nagai

Mamoru Tanihara

Tosiharu Harada

Kousaku Tamari

Yoshiro Okuda

Katsunori Fujimoto

Nobuhiro Katayama

Koichiro Morimoto

Kunio Ikemoto

Nanao Horiishi

Hiromitsu Misawa

Seiichi Takahashi

Masayuki Uegami

Toshiyuki Hakata

Hiroshi Sumita

Masaru Isoai

Shinji Uemoto

Minoru Yamasaki

Katsumi Yamashita

Yosiro Okuda

Jean A Lown

Atsushi Takedoi

Hiroyuki Kondo

Manabu Matsumoto

Kunihiro Kouchi

Yoshitaka Yoshinaga

Hiroki Kamon

An object of the present invention is to enhance a coercive force of magnetic particles by promoting formation of a continuous R-rich grain boundary phase in a crystal grain boundary of a magnetic phase of the particles, and to thereby obtain R-T-B-based rare earth magnet particles further having a high residual magnetic flux density. The present invention relates to production of R-T-B-based rare earth magnet particles capable of exhibiting a high coercive force even when a content of Al therein is reduced, and a high residual magnetic flux density, in which formation of an R-rich grain boundary phase therein can be promoted by heat-treating Al-containing R-T-B-based rare earth magnet particles obtained by HDDR treatment in vacuum or in an Ar atmosphere at a temperature of not lower than 670&#xb0; C. and not higher than 820&#xb0; C. for a period of not less than 30 min and not more than 300 min.

R-T-B-based rare earth magnet particles, and bonded magnets containing R-T-B-based rare earth magnet particles

R-T-B-based rare earth magnet particles are produced by an HDDR treatment which comprises a first stage HD step of heating particles of a raw material alloy having a composition of R, B and Co in an inert atmosphere or in a vacuum atmosphere and then replacing the atmosphere with a hydrogen-containing gas atmosphere in which the raw material alloy particles are held in the same temperature range and a second stage HD step of heating a material obtained in the first stage HD step in which the material is held in the hydrogen-containing gas atmosphere.

R-T-B-based rare earth magnet particles, process for producing the R-T-B- based rare earth magnet particles, and bonded magnet

There are provided a pharmaceutical raw material capable of exhibiting a uniform functionality and producing magnetic particle-containing drugs for diagnosis and medical treatments with a high reproducibility. The pharmaceutical raw material comprises a monodisperse colloid sterile aqueous solution of magnetic iron oxide fine particles having an average particle diameter of 5 to 30 nm, a saturation magnetization of 50 to 90 Am/kg and a coercive force of 0.1 to 1.6 kA/m. The pharmaceutical raw material can be produced by forming magnetic iron oxide fine particles in the form of a colloid aqueous solution, purifying the resultant colloid aqueous solution of superparamagnetic iron oxide particles by water-washing and removing water-soluble salts by-produced upon the reaction from the reaction solution by an ordinary method, and replacing a dispersing medium of the purified colloid aqueous solution with ultrapure water.

Pharmaceutical raw material

The present invention is a method for making highly stable magnetic alloy particles with high coercivities and high saturation magnetization comprising the steps of: a) providing a precursor selected from the group consisting of iron oxide hydroxide particles and iron oxide particles, wherein the precursor particle comprises from about 15 to about 45 atomic % Co based on amount of Fe present, b) reducing the precursor particles to magnetic alloy particles, c) passivating the magnetic alloy particles in an oxygen-containing atmosphere at a temperature between about 20.degree. and 100.degree. C., d) annealing the passivated magnetic alloy particles in an inert atmosphere at a temperature from about 120.degree. to about 450.degree. C., and e) further oxidizing the annealed magnetic alloy particles in an oxygen-containing atmosphere.

Method of producing acicular magnetic alloy particles

Disclosed herein are spindle-shaped magnetic iron based alloy particles containing at least one selected from the group consisting of Ni, Al, Si, P, Co, Mg, B and Zn, which have a particle length of 0.05 to 0.40 .mu.m, a crystallite size of 110 to 180 .ANG., a specific surface area of 30 to 60 m.sup.2 /g, a coercive force of 1,300 to 1,700 Oe and a saturation magnetization (.sigma.s) of not less than 100 emu/g and a process for producing the same.

Spindle-shaped magnetic iron based alloy particles and process for

Disclosed herein are granulated particles for magnetic particles for magnetic recording, comprising: acicular ferric hydroxide oxide particles or acicular iron oxide particles; and at least one selected from the group consisting of semisynthetic starch and semisynthetic cellulose and having a bulk density of not less than 0.3 g/cm.sup.3 and a powdering ratio of not more than 40%, and a process for producing the granulated particles, and magnetic particles obtained from such granulated particles.

Granulated particles for magnetic particles for magnetic recording, and

Spindle-shaped magnetic iron based alloy particles

Disclosed herein are acicular magnetic iron based alloy particles for magnetic recording, containing 1.5 to 10 mol % of B based on Fe (calculated as B) and 1.5 to 10 mol % of Co based on Fe (calculated as Co) in the vicinity of the surfaces of said particles and having a saturation magnetization of not less than 125 emu/g and an S.F.D. value of not more than 0.50, and a process for producing the same.

Acicular magnetic iron based alloy particles for magnetic recording and

Disclosed herein are magnetic iron oxide particles comprising spindle-like magnetite or maghemite particles having an aspect ratio(major:minor) of less than 4:1 and containing 0.1 to 20 atomic % of Si to Fe, and a process for producing the same.

Spindle-like magnetic iron oxide particles and process for producing the

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Aki, Japan

Hirofumi Kawasaki