Toda Kogyo Corporation

Shiseido Company, Limited

Imation Corporation

Yasutaka Ota

Kenji Okinaka

Norimichi Nagai

Kohji Mori

Hirofumi Kawasaki

Katsunori Fujimoto

Akio Mishima

Mamoru Tanihara

Masao Kiyama

Toshio Takada

Akihiko Hirayama

Kousaku Tamari

Tosiharu Harada

Norio Sugita

Masaaki Maekawa

Akinori Yamamoto

Haruki Kurokawa

Yoshiro Okuda

Kunio Ikemoto

Hiroshi Fukui

Takashi Ogawa

Masayuki Uegami

Tsutomu Katamoto

Minoru Yamasaki

Katsumi Yamashita

Jean A Lown

Tsuneo Suhara

Manabu Matsumoto

Kunihiro Kouchi

Hiroki Kamon

Magnetic metal particles containing iron as a main component, comprising cobalt in an amount of usually 20 to 50 atm %, calculated as Co, based on whole Fe, aluminum in an amount of usually 3 to 15 atm %, calculated as Al, based on whole Fe and a rare earth element in an amount of usually 3 to 20 atm %, calculated as rare earth element, based on whole Fe, and having an average major axis diameter of usually 0.02 to 0.065 &#x3bc;m, preferably from 0.02 to less than 0.05 &#x3bc;m, a coercive force of usually 159.2 to 222.9 kA/m (2,000 to 2,800 Oe), a soluble Na content of usually not more than 30 ppm, a soluble Ca content of usually not more than 100 ppm, and an oxidation stability &#x394;&#x3c3;s of usually not more than 10%.

Magnetic metal particles containing iron as main component, process for producing the same and magnetic recording medium using the same

Spindle-shaped magnetic alloy particles containing Fe and Co as main components of the present invention have a cobalt content of 20 to 50 atm % (calculated as Co) based on whole Fe; an average major axis diameter (L) of 0.03 to 0.10 &mgr;m; a coercive force value of 159.2 to 238.7 kA/m (2,000 to 3,000 Oe); a crystallite size of 100 to 160 &angst;; and an activation volume (V ) of 0.01 to 0.07E-4 &mgr;m . A high-density magnetic recording medium produced by using such spindle-shaped magnetic alloy particles containing Fe and Co as main components, have an excellent output characteristics in a short wavelength region, a considerably reduced noise and an excellent storage stability.

Spindle-shaped magnetic alloy particles for magnetic recording, and magnetic recording medium

Magnetic acicular alloy particles containing iron as a main component

The present invention relates to a spindle-shaped goethite particles containing cobalt of 8.0 to 50.0 atm %, calculated as Co, based on the total Fe in the spindle-shaped goethite particles and a compound of at least one element selected from the group consisting of Al, Si, Nd, Y, La, Ce, Pr, Tb, Ca, Mg, Ba and Sr of not more than 25.0 atm %, calculated as the element, based on the total Fe in the spindle-shaped goethite particles, and having an average major axis diameter of 0.05 to 0.15 .mu.m, a size distribution (standard deviation/major axis diameter) of not more than 0.30, an average minor axis diameter of 0.010 to 0.025 .mu.m, an aspect ratio of 4 to 8 and an X-ray crystallite size ratio (D.sub.020 /D.sub.110) of 2.0 to 3.5. These spindle-shaped goethite particles are useful as raw material of spindle-shaped magnetic iron-based alloy particles containing cobalt and iron as the main ingredients, which have a uniform particle size, no inclusion of dendrites, a high coercive force, an excellent coercive force distribution, a large saturation magnetization, and in addition, an excellent stability against oxidation.

Spindle-shaped geothite particles

The disclosure describes spindle-shaped magnetic iron-based alloy particles containing cobalt and iron as the main ingredients in which the Co content is 1.0 to 50.0 atm % (calculated as Co) based on the total Fe in the spindle-shaped magnetic iron-based alloy particles, and which the spindle-shaped magnetic iron-based alloy particles have an average major axis diameter of 0.05 to 0.18 .mu.m, a size distribution (standard deviation/major axis diameter) of not more than 0.25, an average minor axis diameter of 0.010 to 0.020 .mu.m, an aspect ratio (major axis diameter/minor axis diameter) of 4 to 15, an X-ray crystallite size D.sub.110 of 120 to 180 .ANG., a coercive force of 1720 to 2500 Oe, a saturation magnetization of not less than 110 emu/g, and a saturation magnetization decrement percentage of not more than 17%.

Process of making goethite or iron-based alloy particles

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

Spindle-shaped magnetic iron-based alloy particles containing cobalt and

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 acicular magnetic metal particles containing iron as the main ingredient the surfaces of which are coated with a polymer formed from at least one of silicone compounds represented by the following formula (I):

Acicular magnetic metal particles containing iron as main ingredient and

Disclosed herein are plate-like barium ferrite particles with a solid solution of zinc on the surface thereof, which have an average particle diameter of not less than 0.03 .mu.m and less than 0.1 .mu.m, a BET specific surface are of 55 to 80 m.sup.2 /g, a coercive force of 300 to 1,500 Oe and a magnetization of not less than 57 emu/g, preferably not less than 60 emu/g, in magnetic field of 10 KOe, and which are represented by the following formula (I):

Plate-like barium ferrite particles suitable for use in magnetic

Growing community of inventors

Hiroshima, Japan

Yasutaka Ota