Tdk Corporation

Other

Tokyo Magnetic Printing Co., Ltd.

Tdk Electronics Company, Limited

Masao Shigeta

Shohei Mimura

Tsutomu Chou

Masahiro Ito

Asako Kajita

Ippo Hirai

Suguru Takayama

Tsutomu Choh

Chikara Ishizaka

Hiroshi Hosaka

Katsuhiko Wakayama

Kaneo Mohri

Masahiro Karatsu

Kazuo Fukunaga

Norio Sato

Teruhiko Ojima

Motoyoshi Fujita

Atsushi Makimura

Mari Fujii

Tsutomu Cho

Shotatsu Sugenoya

Katsumi Saito

Eiichi Suga

Minoru Higurashi

Hiroyoshi Shimizu

The invention is a magnetic recording medium which is effectively protected against forgery by the alteration of recorded data, and a method for carrying out writing and reading on this magnetic recording medium. The magnetic recording medium of the invention comprises a recording material composed of a crystalline alloy containing Fe and Al . In the recoding material, the total amount of Fe and Al is at least 90 at % and the atomic ratio Al/(Fe&plus;Al) ranges from 0.30 to 0.45. The recording material changes from a disordered phase to an ordered phase by heating. The recording material has a saturation magnetization of at least 45 emu/g prior to heating and lowers its saturation magnetization by at least 35 emu/g upon heating. Dark regions are observable in a bright-field image of the recording material by transmission electron microscopy, the dark regions accounting for 15-60% of the recording material in areal ratio and having a maximum breadth of 10-200 nm.

Magnetic recording medium

A magnetic recording medium, and methods of making and reading the same, including on at least a portion of a substrate an irreversible recording layer which contains an irreversible recording material undergoing an irreversible change of saturation magnetization upon heating. The invention involves the steps of previously heating the irreversible recording layer to form an initial heated region in which a plurality of heated bars whose saturation magnetization has been irreversibly changed are arrayed in a bar code pattern, and converting unheated bars disposed between the heated bars into a heated state for changing the array pattern of heated bars, thereby recording the information.

Magnetic recording medium and method of making the same

A magnetic recording medium, and a method of making the same, including an irreversible recording layer which undergoes an irreversible change of saturation magnetization upon heating. The magnetic recording medium includes on at least a portion of a substrate an irreversible recording layer which contains an irreversible recording material undergoing an irreversible change of saturation magnetization upon heating. The irreversible recording layer includes at least in part a fixed information recording region for recording the fixed information of the medium. In the fixed information recording region, a plurality of heated bars whose saturation magnetization has been irreversibly changed are arrayed substantially parallel to each other. The array pattern of the heated bars or the array pattern of unheated bars disposed between adjacent ones of the heated bars contains the fixed information encoded in a frequency modulation process or phase modulation process.

A soft magnetic alloy having a composition of general formula:

Soft magnetic alloy, method for making, magnetic core, magnetic shield

Soft magnetic alloy comprising Fe, a vitrifying element (Si and B), and Cu, and containing a crystalline phase shows a low magnetic permeability of up to 3,000 at 100 kHz. Magnetic cores formed therefrom have low permeability, a wide unsaturation region, and iso.permeability without forming a gap and find application in choke coils and transformers.

Soft magnetic alloy, method for making, and magnetic core

Soft magnetic powder comprising flat soft magnetic particles of an alloy having a composition defined and encompassed by polygon ABCDE in a Fe-Si-Cr ternary composition diagram of FIG. 1 or polygon JKLMN in a Fe-Si-Al ternary composition diagram of FIG. 4 is suitable for use in magnetic shields. The flat soft magnetic particles are prepared by furnishing alloy particles having a predetermined composition, flattening them, and heat treating the flat particles to develop a peak corresponding to plane index (002) in an X-ray diffraction diagram thereof.

Soft magnetic powder and magnetic shield composition

A powder comprising flakes of magnetically soft amorphous alloy having an average thickness of 0.01-1 .mu.m and an aspect ratio of 10-10,000 is blended with a binder to form a coating composition from which a magnetic shield is fabricated. The alloy is basically an Fe-B-Si ternary alloy in which iron may be partially replaced by another metal.

Magnetic shield-forming magnetically soft powder, composition thereof,

A direction sensor includes at least one sensor element including a ring-shaped core formed from at least one flexible wire made of zero-magnetostrictive amorphous magnetic material, two pairs of series connected coils spaced from each other at equal intervals about the core for sensing an external magnetic field, with the core being formed by threading the wires through the coils, the coils being excited by an alternating frequency f, wherein voltages of frequency f are produced across each pair of coils; and a process circuit for providing a differential voltage between the voltages of frequency f produced across each pair of coils.

Magnetic sensor using the earth's magnetism

The present invention relates to the core of a noise filter. Conventionally, ferrite or iron powder is used as the core of a noise filter. Some patent publications disclose the core of a noise filter made of an amorphous magnetic alloy. An amorphous magnetic alloy which as a low pulse-noise resistance deterioration percentage is that on or within the curve X and Y of FIG. 3.

Core of a noise filter comprised of an amorphous alloy

The present invention relates to a core of magnetic amorphous alloy. A thin strip of such alloy is wound and then cut to provide, e.g., C-shaped pieces. A pair of C-shaped pieces is assembled to provide the core. Conventionally, the magnetic properties, e.g., the watt loss, of the core are impaired at the cut ends of a thin strip due to the formation of burrs. The present invention is characterized by providing the cut ends with a thickness substantially the same as the thickness of the non-cut portion of the thin strip and by polishing the cut ends substantially parallel to the major surface of the thin strip, thereby improving the magnetic properties of the core.

Amorphous cut core

The improved structure of an inductor with an amorphous sheet core and a winding has been found. A core assembly has a pair of housing halves made of non-magnetic material with U-shaped track, in which a laminated amorphous sheet is mounted. The ends of the halves are inserted in a winding so that the ends of the cores abut with each other directly or through a gap spacer. The core halves are pressed by spring action to assemble the inductor. The core halves are produced by the steps of winding an amorphous sheet to a coil, inserting the coil in the track of the housing, and impregnating the coil with plastics.

Inductor

Conventionally, silicon steel strips and ferrite cores have been used as the core of a choke coil. These strips and the like have not yet been replaced with amorphous alloy because in the known amorphous magnetic alloy the pre-magnetization characteristic, the amount of heat generated, and the secular change are poor. The present invention proposes a core of a choke coil which consists of a coiled thin strip of an amorphous alloy, and has at least one cut air gap, the coiled regions of the thin strip being bound to one another at at least in the neighborhood of said at least one cut air gap, and said amorphous magnetic alloy is essentially comprised of the following composition, Fe.sub.x Mn.sub.y (Si.sub.p B.sub.q P.sub.r C.sub.s).sub.z, wherein x+y+z is 100 atomic % based on all of the elements, y is from 0.001 to 10 atomic %, z is from 21 to 25.5 atomic %, p+q+r+s is atomic % 1, p is from 0.40 to 0.75, r is fro 0.0001 to 0.05, the ratio s/q is from 0.03 to 0.4, and z is z.ltoreq.50p+1, z.ltoreq.10p+19, z.gtoreq.30p+2, and z.gtoreq.13p+13.7.

Core of a choke coil comprised of amorphous magnetic alloy

The present invention relates to a saturable core which consists of a coiled thin strip of an amorphous magnetic alloy. The present invention provides a saturable core having a high .DELTA.Bs, a low power loss, a good saturation property, and low secular changes of the magnetic properties, due to determining the coiling direction of the saturable core so that it is the same as that of a coil heat treated.

Growing community of inventors

Narashino, Japan

Masao Shigeta