Centre National De La Recherche Scientifique

Université Paul Sabatier (toulouse Iii)

Universite Paul Sabatier

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Other

Nippon Telegraph and Telephone Corporation

Atochem

S.a. Ateca

Abel C Rousset

Philippe Tailhades

Laurence Bouet

Jean-Pierre Bonino

Paul Mollard

Hiroshi Yoshikawa

Manabu Yamamoto

Takaya Tanabe

Lionel Presmanes

Toshifumi Ohkubo

Michel Gougeon

Akinori Furuya

Xavier DeVaux

Corine Despax

Christiane B Salvaing

Patrick Langlade

Isabelle Pasquet

Yves Blottiere

Bernard Gilot

Christian Sarda

Isabelle Gossart

Claude Rossignol

El Hadj Jabry

Guy Boissier

Val&eacute;rie Carles

Jean-Pierre Caffin

Alain Manoux

Belaid Maachi

A magneto-optical recording medium has a recording layer and a reflective layer on a substrate. The recording layer has a layered structure in which at least one spinel ferrite (or rutile-type oxide or hematite) layer and at least one garnet ferrite layer are piled together. It is preferable that the layered structure is formed on tracks where data are recorded. A manufacturing method comprises the steps of heat treatment in the range of 500-700&#xb0; C., preferably 600-630&#xb0; C., after the formation of the recording layer. In the magneto-optical recording and playback device to record and play back data, the wavelength of light for recording data is different from that for reading data, which is preferable for a magneto-optical recording medium comprising a garnet ferrite layer.

Magneto-optical recording medium, manufacturing method thereof and magneto-optical data recording and playback device

This invention relates to magneto-optical recording media such as magneto-optical disks and cards, manufacturing methods of the medium and a magneto-optical recording and playback device to record and play back data using the magneto-optical recording media. The magneto-optical recording medium of the present invention has a recording layer and a reflective layer on a substrate, and the recording layer has a layered structure in which at least one spinel ferrite (or rutile-type oxide or hematite) layer and at least one garnet ferrite layer are piled together. It is preferable that the layered structure is formed on tracks where data are recorded. The manufacturing method of the present invention comprises the steps of heat treatment in the range of 500-700&deg; C., preferably 600-630&deg; C., after the formation of the recording layer. In the magneto-optical recording and playback device to record and play back data of the present invention, the wavelength of light for recording data is different from that for reading data, which is preferable for a magneto-optical recording medium comprising a garnet ferrite layer.

Opto-magnetic recording medium with a garnet ferrite recording layer, and opto-magnetic information recording/reproducing device

The invention relates to a method of preparing metal powder comprising: preparing a simple or mixed oxalate of one or more metals formed of particles with needle-like morphology having a mean acicularity ratio (length/diameter) of from 4 to 20, and a length of from 5 to 10 microns and converting said oxalate to metal or metal alloy powder by reducing treatment with gaseous hydrogen. The conversion of said oxalate can be carried out by decomposing said oxalate, in air, to an oxide and then reducing said oxide to metal or metal alloy. The metal is chosen from among the rare earth metals and the transition metals, preferably from among iron, cobalt, and nickel. The method is particularly suitable for making iron powder metal having a spongy and filament-like microstructure which makes it suitable for use in heating composition for thermo-piles. In addition, the invention relates to metal compacts unstoved or annealed which are obtained by applying compaction pressure to the powders according to the invention.

Method of preparing metal powders, metal powders prepared in this way and compacts that include these powders

Composite material for magnetooptic recording, comprising a thin layer deposited on a non-magnetic solid substrate. The said thin layer is a polycrystalline layer consisting of microcrystals having a structure of a vacant-site spinel ferrite, based on iron, cobalt and transition metals. By virtue of a particular process for producing the thin layers, enabling especially the size of the crystallites to be increased, it is possible to optimize the magnetic and magnetooptic properties and to obtain thin layers having, for example, a remanent Faraday rotation and a coercive field which are greater, respectively, than 1 degree per micron for the Faraday rotation and 1000 Oe for the coercive field.

Composite material for magnetooptic recording its preparation and its use

The invention relates to nano-composite powders of alumina and metal constituted of grains of micronic size. Each grain comprises a compact matrix of alumina of a specific surface area less than 5 m.sup.2 /g, in which are dispersed crystallites of transition metals of alloys of these metals, of sizes less than 50 nm. The powder according to the invention may be produced starting with a precursor comprised of a mixed carboxylic salt of aluminum and one or more transition metals. The powders according to the invention permit producing by sintering cermets of alumina/metal benefitting from greatly improved mechanical and thermo-mechanical properties.

Composite alumina/metal powders, cermets made from said powders, and

A process for preparing hexaferrite particles of the type M'Fe.sub.12 O.sub.19 wherein M' represents principally an alkaline earth metal involves preparing a particulate mixture of a ferrous salt of an organic acid and a salt of an organic acid with at least one metal M', optionally with at least one dopant agent, the particles of the mixture having a size not greater than about 0.5 .mu.m and the said mixture containing a stoichiometric excess of the salt of metal M'. This mixture is heated up to the decomposition of the organic salts and the resulting product is submitted to a thermal treatment at a temperature at least equal to 700.degree. C. but not greater than 1000.degree. C. and is maintained at this temperature for a period of time sufficient to form hexaferrite. After cooling the resulting particles are washed with an aqueous solution of an acid capable of dissolving formed monoferrites of the type M'Fe.sub.2 O.sub.4 to remove them.

Process for the preparation of hexaferrites

Oxides having the spinel structure of .gamma.-Fe.sub.2 O.sub.3 /Fe.sub.3 O.sub.4 type, substituted by trivalent and monovalent metals, or doped with non-spinel derivatives thereof, more particularly iron/aluminum/potassium oxides well suited as dehydrogenation catalysts, e.g., for dehydrogenating ethylbenzene into styrene, are prepared by thermally decomposing mixed iron, aluminum and potassium salts, notably the oxalates thereof, in the presence of air, then reducing the product of thermal decomposition at a temperature of less than 400.degree. C., advantageously in the presence of steam and hydrogen, and optionally oxidizing the product of reduction; oxides of .beta.-alumina structure are also produced.

.gamma.-Fe.sub.2 O.sub.3 /Fe.sub.3 O.sub.4 spinels

A manganite type composition of the formula

Compositions of transition metal manganites in the form of particles or

Compositions of particulate magnetic oxides with a defect spinel

Particulate compositions of ferromagnetic metal oxalates in the form of

A method for manufacturing continuous, closed and hollow bodies which comprises (a) using cores (25) which are soluble in a solvent, (b) depositing on each core a coating (3) with a suitable mechanical strength to be self-supporting and having open pores to pass a solvent, and (c) placing the cores so coated into a solvent for dissolving the cores; the method of the invention may be implemented in bulk parts, in an economical manner, and allows making hollow bodies, in particular hollow balls, each comprising a continuous skin devoid of any macroscopic perforation and of a kind and with a thickness which are easily adjusted in relation to the desired properties.

Method for making continuous and closed hollow bodies, hollow bodies so

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Ramonville St Agne, France

Abel C Rousset