Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-11-13
2002-07-23
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06424490
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P11-323435 filed Nov. 12, 1999, which applications is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a magnetic head to be suitably used for highly densely recording digital signals on a magnetic recording medium.
2. Related Background Art
Magnetic recording/reproducing apparatus for recording and/or reproducing (hereinafter to be referred to as recording/reproducing) magnetic signals on a tape-shaped magnetic recording medium such as video tape recorders (VTRs) and digital audio tape recorders (DATA recorders) are provided with a magnetic head.
The magnetic head comprises a magnetic core made of a magnetic material and a coil wound around the magnetic core. The magnetic core is provided with a minute magnetic gap.
In the field of magnetic recording in recent years, there is a growing demand for the technology of recording/reproducing ever more magnetic signals at a high speed in order to realize a high image quality of video signals and a high memory capacity and a high transfer rate of recording medium. Efforts have been made to meet the demand by using magnetic signals having a shorter wavelength to be recorded on and/or reproduced from a recording medium by means of a magnetic recording/reproducing apparatus. The recording medium that can meet the demand may be a metal tape obtained by applying powder of a ferromagnetic metal material to a base film or an evaporation type tape obtained by directly depositing a ferromagnetic metal material on a base film by evaporation. Such a magnetic recording medium is highly resistant against magnetic force so that it can stably store and retain high frequency magnetic signals.
As for the magnetic head, there have been proposed magnetic heads wherein a pair of magnetic core halves, each being formed by sandwiching a metal magnetic film between a pair of guard members containing a nonmagnetic material as principal ingredient, are made to abut each other and bonded together at the corresponding end facets of the metal magnetic films and a nonmagnetic film is formed along the interface of the metal magnetic films that are abutting each other in order to produce a magnetic gap.
Such magnetic heads are referred to as multilayer type heads because each of the metal magnetic films of magnetic core has a multilayer structure formed by arranging metal magnetic layers showing a high permeability and a high saturation magnetic flux density with an insulation layer interposed therebetween. Thus, each of the metal magnetic films of a multilayer type head has a multilayer structure formed by arranging metal magnetic layers with an insulation layer interposed therebetween and the metal magnetic films are mutually magneto-statically bonded at corresponding ends thereof. With this arrangement, the eddy-current loss of the head can be reduced and the head efficiency can be improved particularly in a high frequency zone.
Meanwhile, conventional multilayer type heads typically employs gold (Au) as for the material of the nonmagnetic film for forming the magnetic gap. Then, such a nonmagnetic film is formed on the abutting surface of each of the magnetic core halves so that the pair of magnetic core halves may be bonded together by bonding the nonmagnetic films by means of low temperature thermal diffusion bonding. Additionally, a Cr layer may be formed closer to each magnetic core half than the Au layer in conventional multilayer type heads for the purpose of retaining the good adhesion of the Au layer that operates effectively for the low temperature thermal diffusion bonding relative to the corresponding metal magnetic film. Thus, the nonmagnetic film may also have a multilayer structure of a Cr layer and an Au layer.
However, with such an arrangement, the Cr layer of the nonmagnetic film can adhere not only to the guard member of the magnetic core half but also to the metal magnetic film of the magnetic core half. Then, the metal magnetic layer of the multilayer structure of the metal magnetic film becomes short-circuited by the Cr layer to give rise to an increased eddy-current loss. In other words, in a conventional multilayer type head, the effect of the multilayer structure of the metal magnetic film designed for the purpose of reducing the eddy-current loss is offset, if partly, by the Cr layer of the nonmagnetic film for forming the magnetic gap to consequently degrade the performance of the head in a high frequency zone.
BRIEF SUMMARY OF THE INVENTION
Therefore, it is the object of the present invention to provide a magnetic head adapted to prevent any of the metal magnetic layers of its metal magnetic films for forming of the magnetic core from being short-circuited by the nonmagnetic films of the magnetic gap, thereby reducing the eddy-current loss and improving the head efficiency particularly in a high frequency zone. According to the invention, the above object is achieved by providing a magnetic head comprising a pair of magnetic core halves, each being formed by sandwiching a metal magnetic film between a pair of guard members containing a nonmagnetic material as principal ingredient, made to abut each other and bonded together at the corresponding end facets of the metal magnetic films and a nonmagnetic film formed along the interface of the metal magnetic films abutting each other in order to produce a magnetic gap;
each of said metal magnetic films having a multilayer structure formed by arranging metal magnetic layers with an insulation layer interposed therebetween;
said nonmagnetic film having a multilayer structure including a first film of an insulating material, a second film of Cr and a third film of Au as arranged from each of said pair of magnetic core halves, said third films being diffusion bonded to each other.
In a magnetic head according to the invention and having the above described configuration, the electric insulation of the metal magnetic layers of the metal magnetic film can be maintained because the first films of the nonmagnetic film that are held in contact with the respective magnetic core halves are made of an insulating material.
Therefore, the eddy-current loss can be effectively reduced to improve the head efficiency particularly in a high frequency zone. Therefore, a magnetic head according to the invention can stably and reliably record magnetic signals on and reproduce magnetic signals from a magnetic recording medium if the magnetic signals to be recorded on and/or reproduced from the magnetic recording medium have a short wavelength.
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Aoki Kaoru
Kousaka Masaya
Cao Allen
Sonnenschein Nath & Rosenthal
Sony Corporation
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