Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-08-31
2003-09-23
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06624972
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head for generating a magnetic field to magnetize an external medium, a magnetic head manufacturing method of manufacturing a magnetic head, and an information recording apparatus for recording information on a medium.
2. Description of the Related Art
Recently, as a computer is widely used, a large amount of information is usually dealt with. As one of information recording apparatuses for recording such a large amount of information, there is used a hard disk drive (HDD). Generally, a hard disk drive (HDD) has a magnetic disk which is a disk-like shaped medium for storing information, and a recording head for causing information to be stored in the magnetic disk.
The magnetic disk has a ferromagnetic layer consisting of a ferromagnetic material on a surface thereof. Magnetization is independently maintained on each of microscopic areas of the ferromagnetic layer. The magnetic disk is subjected to a high speed rotation inside the HDD. The recording head has a microscopic recording coil and a pair of magnetic poles. Generally, the recording head is disposed to be adjacent to the magnetic disk. The pair of magnetic poles are placed over against one another with a predetermined interval (gap length) in a direction in which a track of the magnetic disk is extended. The pair of magnetic poles have a predetermined width corresponding to the track width in the track width direction. When a signal current conducts through the recording coil, a magnetic field generates from the recording coil in accordance with the signal current. The magnetic field thus generated is leaked from the pair of magnetic poles, so that magnetization of each track on the surface of the magnetic disk is suitably reversed in a microscopic length unit according to the gap length. Such a reversal of the magnetization causes information to be recorded in form of a direction of magnetization of each microscopic domain.
In order to hold magnetization of each microscopic domain of the magnetic disk thus oriented, there is a need that the ferromagnetic layer of the surface of the magnetic disk has a predetermined or more coercive force H
c
. On the other hand, it is needed for a recording head for recording information on the magnetic disk to apply to the magnetic disk such a magnetic field that a magnetic field (a head magnetic field H
h
) in the ferromagnetic layer becomes stronger than the coercive force H
c
of the magnetic disk so that the respective magnetization of the magnetic disk is reversed.
Generally, the magnetic field generated from the recording head is leaked out of the track as the object of the recording. The leaked magnetic field has an effect on direction and magnitude of magnetization out of the track. Generally, it is considered that intensity of the magnetic field at the lower limit, on which the reversal of magnetization occurs, is ½ of the coercive force H
c
of the magnetic disk. Thus, in a range that intensity of the magnetic field leaked out of the track as the recording object is not less than ½ of the coercive force H
c
of the magnetic disk, there is a possibility that the magnetization is reversed also at the out side of the track and whereby recording-stain occurs. The recording-stain is defined in magnitude by a spread in a track width direction as to one end of the range as mentioned above. Generally, the recording-stain becomes relatively larger with respect to the track width, as the track width becomes smaller. Accordingly, the recording-stain is an obstacle to recording information onto the magnetic disk at high recording density. In order to reduce the recording-stain, there is a method of reducing the gap length whereby a leakage of the magnetic field to the out side of the track as the recording object is suppressed.
However, when the gap length is reduced, reversal of magnetization by the recording head in the track as the recording object is performed in the narrow range in the track direction according to the gap length. As the range is narrower, a demagnetizing field of the reversed magnetization is increased, and as a result, intensity of the magnetic field generated from the recording head is weaken by the demagnetizing field. In this manner, when intensity of the magnetic field is weaken, there occurs a shift (a hard transition shift: HTS) of a magnetization transition point at the boundary of an area wherein magnetization is reversed, and as a result, a range in which magnetization is actually reversed, that is, a range in which the recording magnetic field exceeds the medium H
c
, is narrowed. This causes overwrite characteristics of recording of information onto the magnetic disk by the recording head, that is, a ratio of reproducing output of information newly recorded to reproducing output of information before overwriting still remained in the event that information is overwritten on the magnetic disk, to deteriorate. As mentioned above, according to the conventional recording head, it is difficult to cope with both reducing the recording-stain and providing excellent overwrite characteristics.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a magnetic head having excellent overwrite characteristics capable of reducing the recording-stain, a magnetic head manufacturing method of manufacturing the magnetic head, and an information recording apparatus having excellent overwrite characteristics capable of reducing the recording-stain.
To achieve the above-mentioned objects, the present invention provides a magnetic head having a pair of magnetic poles disposed to be adjacent to or in contact with a recording medium relatively moving, said pair of magnetic poles being placed over against one another with a predetermined interval in a relative moving direction at an adjacent point or a contact point to the recording medium, in which a magnetic field is generated between the magnetic poles so that the recording medium is magnetized,
wherein a soft magnetic film expanding in a direction blocking facing of the pair of magnetic poles and a non-magnetic film supporting the soft magnetic film are alternately laminated at a position located between the pair of magnetic poles.
In a magnetic head, generally, one or both of a pair of magnetic poles constituting the magnetic head is provided with a sub-magnetic pole at the end wherein the pair of magnetic poles face one another. A spatial distribution of a magnetic field generated between the pair of magnetic poles is controlled by the sub-magnetic pole in accordance with shape, size and material of the sub-magnetic pole. In the event that a magnetic head of the present invention, a magnetic head referred to in a magnetic head manufacturing method of the present invention, which will be described later, and a magnetic head referred to in an information recording apparatus of the present invention, which will be also described later, have such a sub-magnetic pole, the magnetic pole referred to in the present invention implies such a sub-magnetic pole.
Generally, according to a magnetic head, when a predetermined interval is spread between a pair of magnetic poles, HTS is suppressed to be small and an overwrite characteristic is improved. On the other hand, the soft magnetic film is magnetized by a magnetic field generated between the pair of magnetic poles to attract a flux, and thus even in the event that the interval between the pair of magnetic poles is spread, the soft magnetic film serves to suppress a recording-stain in a direction along the recording medium perpendicular to the relative moving direction, that is, a so-called track width direction. Thus, in the event that a predetermined interval is ensured between the pair of magnetic poles, according to the present invention, it is possible to provide a magnetic head coping with both the reduction of the recording-stain and the excellent overwrite characteristic.
In the magnetic head of the present inventi
Nishida Syuji
Tagawa Ikuya
Fujitsu Limited
Greer Burns & Crain Ltd.
Tupper Robert S.
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