Toda Kogyo Corporation

Akio Mishima

Kenji Okinaka

Yasutaka Ota

Tosiharu Harada

Kohji Mori

Hirofumi Kawasaki

Akira Mukaizaka

Norimichi Nagai

Mamoru Tanihara

Yoshiro Okuda

Tomoyuki Imai

Kousaku Tamari

Katsunori Fujimoto

Yosiro Okuda

Kunio Ikemoto

Masayuki Uegami

Hiroshi Sumita

Minoru Yamasaki

Katsumi Yamashita

Tokihiro Kurata

Hiroyuki Kondo

Manabu Matsumoto

Kunihiro Kouchi

Yoshitaka Yoshinaga

Hiroki Kamon

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 is spindle ferromagnetic alloy particles having the aspect ratio (major:minor) of less than 3:1 and the coercive force of 500 to 100 Oe, and containing 0.1 to 13 atomic % of Si to Fe, and a process for producing the same.

Spindle ferromagnetic alloy particles

Disclosed herein is acicular ferromagnetic alloy particles for magnetic recording, containing Si, Cr, Ni and P and optionally Mg impregnated with phosphorus compound and silicon compound and process for producing the same.

Acicular ferromagnetic alloy particles for magnetic recording and

Acicular ferromagnetic alloy particles doped with silicon, chromium and nickel and optionally magnesium and a process for producing said particles comprising heating at 300.degree. to 500.degree. C. under reducing atmosphere acicular particles of .alpha.-iron(III) oxide hydroxide doped with silicon, chromium and nickel and optionally magnesium or acicular particles of .alpha.-ferric oxide doped with silicon, chromium and nickel and optionally magnesium obtained by dehydrating the acicular particles of .alpha.-iron(III) oxide hydroxide doped with silicon, chromium and nickel and optionally magnesium are disclosed herein.

Acicular ferromagnetic alloy particles and process for producing said

A process for producing an acicular ferromagnetic alloy particles mainly containing iron and magnesium, which comprises preparing a suspension of iron(II) hydroxide and water-soluble magnesium salt, the suspension having a pH value of at least 11 and containing the magnesium salt in an amount of 0.5 to 20.0 atomic % based on the amount of the iron(II) hydroxide in the suspension and calculated as the ratio of Mg to Fe(II), oxidizing the suspension with an oxygen-containing gas to form an acicular particles of iron(III) oxide hydroxide substituted with magnesium, forming coats of phosphorus compound and subsequent silicon compound on the acicular particles, heating the resultant particle at 500.degree. to 900.degree. C. under a non-reducing atmosphere and then reheating the particle thus treated at 350.degree. to 600.degree. C. under reducing atmosphere.

Process for producing acicular ferromagnetic alloy particles and

Fine magnetic particles with high saturation magnetization (over 140 emu/g) as well as high stability against oxidation in air, are produced by a process which comprises the first stage of oxidizing the surfaces of metallic particles consisting mainly of iron in an atmosphere containing both H.sub.2 O and H.sub.2 gases at an oxidizing temperature below 900.degree. C., and the second stage of further oxidizing the surfaces of the particles produced at the first stage in an atmosphere containing O.sub.2 gas.

Process for preparing magnetic particles with metallic region therein,

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Hiroshima, Japan

Akio Mishima