Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-06-14
2003-03-11
Vo, Peter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603070, C029S603130, C029S603140, C029S603230, C204S192100, C205S183000, C360S119050, C360S125330, C360S314000, C360S324000
Reexamination Certificate
active
06530141
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a novel thin film magnetic head, a recording/reproduction separation type head using the thin film magnetic head, and a magnetic recording and reproducing apparatus.
A thin film magnetic head for a magnetic disk apparatus is formed on a slider held above a disk which rotates at high speed. The magnetic head has a magnet pole layer in the form of a thin film made of a ferromagnetic material. On an air bearing surface (ABS), a lower magnetic pole layer and an upper magnetic pole layer are provided on and under a gap layer. The upper and lower magnetic pole layers of the recording head are in contact with each other in the rear part of the gap. In order to increase the recording density, it is necessary to write a large amount of data on the surface of a magnetic disk. For this purpose, it has been proposed to narrow the track width, thereby increasing the recording density. A method which provides a thin film magnetic head having a width at the magnetic pole end, that is, a track width, of 2 &mgr;m or narrower is described in Japanese Patent Application Laid-Open No. 7-296328. According to the method described in this publication, when a magnetic film is formed by plating, a silicon dioxide layer is used as a plating frame. It is described in the publication that the magnetic pole layers from the ABS to the zero throat level in the rear part are wider than a magnetic pole end layer and are in parallel, and that a parallel path is formed for receiving and transferring the magnetic flux from/to the magnet pole end region, thereby enhancing the magnetic flux transmitting ability. Further, the shape of the upper magnetic film (shown by P2(T) in
FIG. 24 and P
2 in
FIG. 25
) is clearly shown in the head construction diagram of
FIGS. 24 and 25
of the publication. The cross-sectional area of the upper magnetic film is constant, when it is seen from the air bearing surface at the gap depth position (upper part of the frame).
It is an object of the invention to provide a thin film magnetic head with less blur having a high recording magnetic field, and a recording/reproduction separation type magnetic head using the thin film magnetic head as well as a magnetic recording and reproducing apparatus.
It is another object of the invention to provide a high-frequency driven magnetic head having a magnetic pole width of 1 &mgr;m or narrower and a magnetic recording and reproducing apparatus which uses the magnetic head and has a very high recording density.
SUMMARY OF THE INVENTION
According to the invention, there is provided a thin film magnetic head having an upper magnetic film and a lower magnetic film disposed on either side of a non-magnetic gap film, wherein on at least one of the upper and lower magnetic films, an upper end part magnetic film is formed on the upper magnetic film and a lower end part magnetic film is formed on the lower magnetic film via the magnetic gap at the ends in which the magnetic gap is formed on the magnetic gap side.
The invention is also characterized in that a cross-sectional area parallel to the air bearing surface of at least one of the upper and lower end part magnetic films is smaller than the cross-sectional area of the upper and lower magnetic films in a part having the magnetic gap; the track width of at least one of the upper and lower end part magnetic films is narrower than the track width of the upper magnetic film and that of the lower magnetic film; and at least one of the upper and lower end part magnetic films is projected more than the upper and lower magnetic films on the air bearing surface toward the air bearing surface side.
According to the invention, the thin film magnetic head as mentioned above is characterized by either one of the following two features or the combination thereof; i.e., (1) the fact that each of the upper and lower end part magnetic films is constructed by a plated magnetic film having a saturated magnetic flux density of 1.5 tesla or higher and the upper magnetic film is formed by plating or sputtering so as to have the width wider than a frame width of the plated magnetic film and a specific resistance of 50 &mgr;&OHgr;·cm or higher; and (2) the fact that the upper and lower end part magnetic films have the same track width, an upper shield film for magnetically shielding the upper magnetic film and a magnetic resistive film has a width wider than the track width, and the upper magnetic film is constructed by one or a plurality of multilayered magnetic films.
According to the invention, there is provided a recording/reproduction separation type magnetic head, in which a recording head for writing information and a reproduction head for reading information are integrally formed, wherein the recording head, is constructed in the form of the above mentioned thin film magnetic head.
In the above mentioned recording/reproduction separation type magnetic head according to the invention, the reproduction head includes a ferromagnetic layer having a magnetic resistive effect and an antiferromagnetic layer which is closely attached to the ferromagnetic layer and allows the ferromagnetic layer to exhibit one-way anisotropy, and the antiferromagnetic layer is made of a Cr—Mn alloy.
According to the invention, a magnetic recording/reproduction apparatus, which comprises a thin film magnetic disk, on which information is recorded, rotating means for the thin film magnetic disk, a recording/reproduction separation type magnetic device which is attached to a floating type slider and has a recording head for writing information and a reproduction head for reading information, and moving means for supporting the floating type slider and accessing the thin film magnetic disk; wherein, the magnetic disk, rotating at 4000 rpm or higher for recording and reproduction and having a recording frequency of 45 MHz or higher, is characterized in that it is accessed by a recording/reproduction separation type magnetic head constructed using the foregoing recording/reproduction separation type magnetic head.
Preferably, the invention is applied to a magnetic disk apparatus having a recording density of 4 Gb/in
2
or higher When a recording head is seen from the air bearing surface, as shown in
FIG. 1
, the track width of the magnetic film
1
above the gap is narrowed relative to a track width Tw near the gap, and the upper end part magnetic film
16
shown in
FIG. 2
is widened on both sides of the track by the length t of the overhang. A frame member having an undercut is fabricated by the combination of irradiation of ultraviolet rays and far ultraviolet rays and two stages of development of a two-layered film using a photo resist and polydimethylglutarimide; a gap film is formed between the photo resist layers; and the lower magnetic film is undercut.
When a magnetic head having the structure, as shown in
FIG. 3
according to the invention, is fabricated, since a frame member made of silicon dioxide or the like is not used, the wear resistance and an apparatus for forming the frame member become unnecessary. Since the upper magnetic film
11
is not exposed to the air bearing surface, as shown in
FIG. 3
, there is little leakage of the magnetic flux from the upper magnetic film to the air bearing surface, so that blur on the medium can be reduced. As shown in
FIG. 6
, when the shape of the upper magnetic film is changed in the throat height, the cross-sectional area on the air bearing surface side parallel to the air bearing surface is reduced, which is enlarged from the middle of the throat height. Consequently, the magnetic field which leaks from the upper magnetic film
11
to the air bearing surface is reduced, and the magnetic field which leaks from the upper magnetic film
11
via the upper end magnetic film
17
can be increased. The head can be used for a magnetic recording apparatus of high recording density having a surface recording density of 4 Gb/in
2
or higher. It is very important for the narrow track head to have a reduced overhang t near the air bearin
Fukui Hiroshi
Fuyama Moriaki
Hara Miki
Ito Tetsuo
Komuro Matahiro
Nguyen Donghai D.
Vo Peter
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