Matsushita Electric Industrial Co., Ltd.

Keiichi Ochiai

Nobuyuki Aoki

Masaki Aoki

Hideo Torii

Hideaki Komoda

Eiji Fujii

Hideo Hatanaka

Yasuhiro Ueyama

Tetsuo Satake

Ikuo Ota

In the magnetic recording medium, the non-magnetic substrate has an under-coat layer including the first flake powder of non-magnetic material on its surface and further has a back-coat film including the second flake powder of non-magnetic material on the opposite face on the non-magnetic substrate to the one face coated by the magnetic film; thereby splendid property of running durability and electromagnetic transducing characteristics is achieved in spite of thinning the total thickness of the magnetic recording medium.

Magnetic recording medium

Disclosed herein is a magnetic recording medium having a magnetic layer comprising hexagonal ferrite magnetic particles each expressed as BaO.multidot.Fe.sub.12-x-y Sn.sub.x Mg.sub.y O.sub.18 (where, 0.55.ltoreq.x.ltoreq.0.88, 0.71.ltoreq.y.ltoreq.1.05). The hexagonal ferrite magnetic particles contained in this magnetic layer each have Sn and Mg partially substituted for Fe, the Sn and Mg being perfectly solid-soluble, thus being capable of providing hexagonal ferrite magnetic particles which are superior in crystalline properties and small in variation of composition. As a result, the coercivity distribution can be made further sensitive, both the self demagnetization and recording demagnetization in the short wave-length range can be reduced, and a higher reproducing output characteristic is attainable in the high density recording range.

Magnetic recording medium having a magnetic layer comprising hexagonal

Disclosed herein is a perpendicular magnetic film of spinel type iron oxide formed on a surface of a base substrate in the form of columnar grains which are densely arranged perpendicularly to the surface of the base substrate. A vapor of an organic iron compound or a mixed vapor consisting of the organic iron compound vapor and a vapor of an organic metal compound different from the organic iron compound is added with oxygen to obtain a mixed gas. The mixed gas is subjected to chemical vapor deposition on the substrate at low temperature, at reduced pressure in plasma, thereby to obtain the perpendicular magnetic film.

Perpendicular magnetic film of spinel type iron oxide compound and its

Disclosed is a composite magnetic powder comprising two crystal phases of a hexagonal ferrite portion and a spinel structure ferrite portion, which are different in thermal characteristic and in crystal structure and which are in a crystallographically epitaxial relation in each particle. The magnetic powder can be synthesized by reaction of starting components in a low temperature solution. Using the magnetic powder, a vertical magnetic recording medium can be provided, which is excellent in weather stability and suitable for short wavelength recording.

Composite magnetic powder, method for producing the same and recording

The present invention provides a platelike magnetic powder made from a magnetic powder having particles each of which has a portion comprising the spinel type crystal structure and a portion comprising the magnetoplumbite type crystal structure. The magnetic powder provides a large saturation magnetization .sigma.s and a small temperature change .DELTA.Hc/.DELTA.T of coercive force in the vicinity of the room temperature. Further, the present invention is to provide a high density magnetic recording medium which uses the magnetic powder. Furthermore, the present invention is to provide, a method to easily manufacture the magnetic powder by the coprecipitation method. A raw material powder of superfine particles is prepared. The prepared powder is fired at a low temperature in a non-oxidizing atmosphere.

Growing community of inventors

Hirakata, Japan

Keiichi Ochiai