Dynamic magnetic information storage or retrieval – Head – Head surface structure
Reexamination Certificate
2001-08-23
2004-10-12
Korzuch, William (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Head surface structure
C360S317000
Reexamination Certificate
active
06804083
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magnetic heads.
2. Description of the Related Art
With respect to magnetic heads used in video cassette recorders (VCRs), data storage equipment for computers, etc., as recording density is improved and the signal-recording mode is digitized, track width continues to decrease from year to year.
In view of these circumstances, various metal-in-gap (MIG) type magnetic heads have been used in which two magnetic core halves are bonded together by a bonding agent, such as a welding glass, with an insulating film disposed therebetween. Each magnetic core half comprises a core half formed of a ferrite or a ceramic provided with a metal magnetic film having superior soft magnetic properties.
Moreover, in recent years, for the purpose of further decreasing the track width as compared to the MIG-type magnetic heads, attempts have been made to use magnetic heads which are provided with magnetoresistive elements (MR elements) for reading magnetically recorded information. These magnetic heads have been used in VCRs, data storage equipment, etc.
FIG. 9
is a sectional view showing a principal part of a conventional magnetic head provided with an MR element, and
FIG. 10
is a schematic diagram of a principal part of the magnetic head viewed from a medium-sliding surface.
In
FIGS. 9 and 10
, the X direction represents the track width direction of the magnetic head, the Y direction represents the travelling direction of a magnetic recording medium as well as the gap length direction of the magnetic head, and the Z direction represents a direction perpendicular to the medium-sliding surface as well as the height direction of the magnetic head. Therefore, the Y direction corresponds to a downstream direction relative to the magnetic recording medium, and a direction opposite to the Y direction corresponds to an upstream direction relative to the magnetic recording medium.
The magnetic head is a so-called “medium-sliding type” magnetic head, and includes two core halves, and an MR head for reading and a write head for recording formed between the core halves.
As shown in
FIGS. 9 and 10
, an MR head
110
for reading is disposed on an insulating layer
104
formed on an end face
103
a
of a core half
103
, and includes a lower shield layer
112
deposited on the insulating layer
104
, a lower insulating layer
113
, a magnetoresistive element (hereinafter referred to as an MR element)
120
formed on the lower insulating layer
113
and exposed to a medium-sliding surface
102
, an upper insulating layer
114
, and an upper shield layer
115
.
The MR element
120
comprises a soft magnetic alloy thin film formed of an Ni—Fe alloy or the like, and is connected to an MR electrode
121
.
A write head
111
includes a lower core layer
115
′ deposited on the upper shield layer
115
, a gap layer
116
deposited on the lower core layer
115
′, a thin-film coil section
117
, an upper insulating layer
118
covering the thin-film coil section
117
, and an upper core layer
119
connected to the gap layer
116
. A base
119
b
of the upper core layer
119
is magnetically coupled to the lower core layer
115
′ substantially at the center of the thin-film coil section
117
.
A core-protection layer
130
composed of alumina or the like is deposited on the upper core layer
119
.
As shown in
FIG. 10
, an insulating sliding-surface layer
131
is provided on both sides in the track width direction (in the X direction) of the MR head
110
and write head
111
and on one side in the gap length direction (the direction opposite to the Y direction) of the write head
111
. The insulating sliding-surface layer
131
, the MR element
120
, the upper and lower shield layers
112
and
115
, the upper and lower core layers
115
′ and
119
, and the gap layer
116
constitute the medium-sliding surface
102
. The insulating sliding-surface layer
131
is composed of the same material as the insulating layer
104
and the upper and lower insulating layers
113
and
114
, and these layers are connected and integrated.
In the MR head
110
, when a sensing current supplied from the MR electrode
121
flows through the MR element
120
, if a recording magnetic field from the magnetic recording medium is applied to the MR element
120
, the resistance of the MR element changes, and thereby the voltage of the sensing current is changed in response to the recording magnetic field. By detecting the change in voltage, magnetically recorded information recorded in the recording medium can be read out.
Although both the upper shield layer
115
and the lower core layer
115
′ are composed of magnetic materials, the functions of the individual layers differ from each other. Thus, the magnetic properties required are different. That is, the upper shield layer
115
must have a high magnetic permeability because it functions as a magnetic shield for the MR head
110
, and the lower core layer
115
′ must have a high magnetic flux density because it functions as a magnetic pole for the write head
111
. Therefore, for example, an Ni-rich Ni—Fe alloy is used for the upper shield layer
115
and an Fe-rich Ni—Fe alloy is used for the lower core layer
115
′. Since the Fe-rich Ni—Fe alloy used for the lower core layer
115
′ has a relatively low hardness and is therefore malleable, a plastic flow can easily occur during grinding.
However, in the conventional magnetic head, as shown in
FIG. 11
, when a magnetic recording medium, such as a magnetic tape, slides over the lower core layer
115
′, a portion of the lower core layer
115
′ may be ground and plastic flow may occur, resulting in a lingulate sag D (see the right side in FIG.
11
). In some cases, so-called “smearing” may occur in which the lingulate sag D extends to the MR element
120
, causing short-circuiting between the lower core layer
115
′ and the MR element
120
, and decreasing the reading output thereby, resulting in the magnetic head having a shortened life span.
Recently, there has also been a demand for decreasing the gap length of the MR head
110
based on the need for an improvement in magnetic recording density. Consequently, the thicknesses of the MR element
120
and the upper and lower insulating layers
114
and
113
have been decreased.
A decrease in the thickness of the upper insulating layer
114
means a decrease in the distance between the MR element
120
and the lower core layer
115
′, and this often results in smearing.
The problem described above does not relate to so-called “floating-type magnetic recording” in which writing and reading of recorded information are performed while the magnetic head and the magnetic recording medium are moved relative to each other without making contact. However, smearing may be unavoidable when a medium-sliding-type magnetic head is employed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a magnetic head in which smearing due to the plastic flow of the lower core layer is prevented so that the magnetic head has a longer life and is suitable for higher recording densities.
In one aspect of the present invention, a magnetic head includes an MR head and a write head which are exposed to a medium-sliding surface, wherein the MR head includes a magnetoresistive element and slides over a magnetic recording medium to read information magnetically recorded in the magnetic recording medium. The MR head further includes a shield layer provided on one side in the thickness direction of the magnetoresistive element, and a shield core layer which includes a shield section and a core section provided on the other side in the thickness direction of the magnetoresistive element, the magnetoresistive element, the shield layer, and the shield section being exposed to the medium-sliding surface. A smear-preventing layer is provided between the shield section and the core section in the shield core layer, the smear-preventing layer
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Korzuch William
Magee C R
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