Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-07-13
2001-10-16
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S122000
Reexamination Certificate
active
06304415
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin-film magnetic head in which magnetic saturation is controlled at the tip portion when a track thereof narrows.
2. Description of the Related Art
Recently, high densifying of magnetic recording density progresses. For example, in HDD system, a system which is feasible to realize the high recording density of 1 Gbpsi/inch
2
becomes commercially practical, and it is nevertheless required to densify recording density. For achieving the high densifying of magnetic recording, such technical challenges as make a recording track of a thin-film magnetic head narrower in width, enlarge recording field with the thus narrowed track, and make magnetic inclination steeper in recording magnetic distribution in a line direction are remained for the persons in the art.
FIG. 18
depicts a structure of a thin-film magnetic head as a conventional and typical recording head. In
FIG. 18
, reference numeral
1
indicates a lower magnetic pole. An upper magnetic pole
3
is formed over the lower magnetic pole
1
with a recording magnetic gap
2
therebetween. The upper magnetic pole
3
has an air bearing surface (ABS) which is shaped corresponding to the track width. The upper magnetic pole
3
has a fan shape extending backward or to a coil (not shown) from the proximity of the air bearing surface. With the magnetic pole
3
having the shape shown in
FIG. 18
, the tip portion corresponding to the narrowed track width is hardly processed with high accuracy in the conventional manufacturing process of heads. Furthermore, magnetic saturation occurs at a narrow portion of the magnetic pole
3
(neck portion
4
), so that it is difficult to generate large recording magnetic field.
For increasing recording magnetic strength, the same structure as that of the MIG (Metal In Gap) head which is used in a bulk head is conducted experiments on the thin-film magnetic head. A thin-film magnetic head provided with a magnetic material layer which has a high saturated magnetic flux density with an extra-thin thickness of about 0.2 &mgr;m at a portion opposing to a magnetic gap is particularly known. When the recording track width of the thin-film magnetic head is narrowed, in a laminated film of two magnetic material layers with different saturated magnetic flux densities, the magnetic saturation occurs at the side of a lower saturated magnetic flux density layer. Accordingly, not only recording magnetic field strength decreases but also magnetic field inclination reduces, thus losing resolution, so that a disadvantage such as deterioration of NLTS (Non linear Transition Shift) happens.
A T-shaped thin-film magnetic head shown in
FIG. 19
is also suggested to prevent magnetic saturation at a portion being narrowed near the tip of a magnetic pole. The thin-film magnetic head shown in
FIG. 19
is provided, at the proximity of the air bearing surface of at least one magnetic pole (upper magnetic pole
5
in FIG.
19
), with a magnetic pole chip
5
a
contacting with the recording magnetic gap
2
and an auxiliary magnetic pole
5
b
which is wider than the magnetic pole chip in a state to have T-shaped figure at the air bearing surface of the magnetic pole
5
.
The T-shaped magnetic pole
5
, as shown in
FIG. 20
, can be realized by means of opening a trench
7
with a predetermined track width in an insulation layer
6
formed on the recording magnetic gap
2
and forming by embedding magnetic material layers in the trench
7
. In the T-shaped magnetic pole
5
using the trench
7
, since the magnetic pole
5
a
can be changed in the shape and the position thereof in accordance with the shape of the trench, the magnetic pole chip
5
a
with narrowed track can be accurately obtained.
However, when the surface width of the magnetic pole chip
5
a
opposing to the gap is narrowed for ever-more narrowing of the track width in the T-shaped magnetic pole
5
, the magnetic saturation occurs because of magnetic flux concentration at the laminated portion (the contacting portion) between the magnetic pole chip
5
a
and the auxiliary magnetic pole
5
b
. In this case, disadvantages of decreasing recording magnetic field strength and magnetic field inclination happen.
It is also investigated that the magnetic pole chip
5
a
in the T-shaped magnetic pole
5
is made with magnetic materials having a saturated magnetic flux density which is higher than that of the auxiliary magnetic pole
5
b
. However, the troublesome magnetic saturation at the laminated portion between the magnetic pole
5
a
and the auxiliary magnetic pole
5
b
is not completely prevented with the foregoing structure.
To be more specific, when the recording magnetic field is enlarged to increase the recording magnetic field strength, the magnetic saturation tends to break out at the laminated portion between the magnetic pole chip
5
a
and the auxiliary magnetic pole
5
b
. If the magnetic saturation occurs at the laminated portion, enough electric current can not be sent into the magnetic pole chip
5
a
made of the magnetic material having high saturated magnetic flux density, so that the magnetic field strength can not be improved in proportion to the increase of the recording current. Furthermore, the magnetic gradient in the line direction lowers because of magnetic field leaked out from portions where the magnetic saturation occurs, then raising a deterioration in NLTS.
As described above, the conventional thin-film magnetic head involves such disadvantage as tend to cause the magnetic saturation at any portion in the head when narrowing. Since the magnetic saturation in the magnetic head causes the recording magnetic field strength and the magnetic field gradient to lower and further NLTS to deteriorate, high densifying of the magnetic recording density is prevented.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a magnetic head which enables to control magnetic saturation at the proximity of the front portion in a magnetic pole to obtain excellent magnetic field strength and magnetic field gradient when the recording width is narrowed.
A first magnetic head according to the present invention is characterized by comprising a magnetic gap which is positioned to be situated on an air bearing surface, a pair of magnetic poles which are positioned to hold the magnetic gap therebetween and at least one of which being composed of a T-shaped magnetic pole having a magnetic pole chip contacting with the magnetic gap and an auxiliary magnetic pole which is wider than the magnetic pole chip, and a coil which is positioned between the pair of magnetic poles to intersect the magnetic poles, wherein the T-shaped magnetic pole has a laminated film including two or more kinds of magnetic material layers each having a different saturated magnetic flux density, and a magnetic material layer which is positioned at a side of the magnetic gap and has high saturated magnetic density out of the magnetic material layers in the laminated film, composing the magnetic pole chip and a portion of the auxiliary magnetic pole close thereto.
In the first magnetic head, not only the magnetic pole chip which composes the tip portion in the magnetic pole but also a portion of the auxiliary magnetic pole near the magnetic pole chip are composed with a magnetic material layer having high saturated magnetization. Accordingly, magnetic saturation is controlled at the contacting portion between the magnetic pole chip with a narrow width corresponding to the track width and the auxiliary magnetic pole. By controlling magnetic saturation at the portion between the magnetic pole chip and the auxiliary magnetic pole, preferable recording magnetic field strength and magnetic field gradient can be attained when the recording track is narrowed. Specifically, when recording current is increased to raise recording magnetic field strength, enough magnetic field strength can be attained corresponding to the electric current, furthermore, steepness of magnetic
Hara Michiko
Hori Akio
Kobayashi Tadahiko
Koizumi Takashi
Nagata Tomohiko
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tupper Robert S.
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