Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1998-12-09
2001-03-13
Cao, Allen T. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06201669
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistive element for regenerating a line of magnetically recorded information by taking advantage of an element in which electric resistance varies in response to changes of external magnetic fields. The present invention in particular relates to a magnetoresistive element and a method for producing the same, wherein flattening of the top face of the magnetoresistive element is attained without deteriorating regenerative characteristics.
2. Description of the Related Art
FIG. 7A
is a cross section, in the vicinity of an ABS (Air Bearing Surface), of an AMR (Amisotropic Magnetoresistive) element for sensing recording magnetic field from a recording medium such as a hard disk device.
A so-called inductive type write magnetic head is laminated on this AMR element.
A soft magnetic layer (SAL)
20
, a non-magnetic layer (SHUNT layer)
21
and a magnetoresistive layer (MR layer)
22
are laminated on the foregoing AMR layer from the bottom to the top and hard bias layers
24
,
24
and lead layers
26
,
26
are laminated on both side areas of this laminated body.
Interlayers
25
,
25
for improving heat resistance are formed between the hard bias layer
24
and lead layer
26
with a protective layer
23
formed on the magnetoresistive layer
22
. Both of the interlayers
25
and protective layer
23
are formed of Ta films.
Usually, a film of a Ni—Fe—Nb alloy is used for soft magnetic layer
20
, a Ta film is used for the non-magnetic layer
21
, a film of a Ni—Fe alloy is used for the magnetoresistive layer
22
, a film of a Co—Pt alloy is used for the hard bias layer
24
and a Cr film is used for the lead layer
26
.
The hard bias layer
24
functions as a magnet magnetized along the X-direction in this AMR element, a bias magnetic field being applied from hard bias layer
24
to the magnetoresistive layer
22
along the X-direction. A bias magnetic field is also applied from the soft magnetic layer
20
to the magnetoresistive layer
22
along the Y-direction. Applying bias magnetic fields to the magnetoresistive layer
22
along the X- and Y-directions allows magnetization changes of the magnetoresistive layer
22
to linearly respond against magnetic field changes.
A sensing current from the lead layer
26
is imparted to the magnetoresistive layer
22
. Since the scanning direction of the recording medium such as a hard disk device is along the Z-direction, changes of the magnetization direction of the magnetoresistive layer
22
allows resistance values to be changed when a leakage magnetic field from the recording medium is applied along the Y-direction, which is sensed as voltage changes.
While an inductive head is laminated on the AMR element via a top gap layer (not shown in the drawing) as hitherto described, the inductive head is composed of a bottom core layer (top shield layer)
40
, a top core layer
41
and a coil layer (not shown in the drawing).
When a recording current flows through the coil layer, a recording magnetic field is imparted to the top core layer
41
and bottom core layer
40
, magnetic signals being recorded on the recording medium such as a hard disk device by a leakage magnetic field between the bottom core layer
40
and top core layer
41
.
FIG. 9
is a cross section in the vicinity of the ABS of a spin-valve type thin film element (a spin-valve type thin film magnetic head) for sensing recording magnetic field from the recording medium such as a hard disk device. An inductive head composed of the bottom core layer
40
and the top core layer
41
shown in
FIG. 7A
is also laminated, though not shown in the drawing, on the spin-valve type thin film element.
The spin-valve type thin film element described above is a kind of GMR (giant magnetoresistive) element, having a better regeneration sensitivity than the AMR element for complying with the requirement of high density recording.
An underlayer
34
such as Ta, an antiferromagnetic layer
30
, a fixed magnetic layer (a pinned magnetic layer)
31
, a non-magnetic conductive layer
32
and a free magnetic layer
33
are laminated from the bottom to the top in this spin-valve type thin film element, and a protective layer
23
made of, for example, Ta is formed on the free magnetic layer
33
as in the AMR element shown in FIG.
7
A.
Hard bias layers
24
,
24
are formed, as in the AMR element shown in
FIG. 7A
, at both side areas of the laminated body from the underlayer
34
through the protective layer
23
, lead layers
26
,
26
being formed on these hard bias layers
24
,
24
via the interlayers
25
,
25
.
A film of a Ni—Mn alloy, a film of a Ni—Fe alloy and a Cu film are usually used for the antiferromagnetic layer
30
, pinned magnetic layer
31
and free magnetic layer
33
, respectively.
The antiferromagnetic layer
30
and the pinned magnetic layer
31
are formed in contact relation with each other as shown in the drawing. The pinned magnetic layer
31
is put into a single magnetic domain state by exchange magnetic coupling at the interface with the antiferromagnetic layer
30
, the magnetization direction of which being fixed along the Y-direction.
The magnetization direction of the free magnetic layer
33
is aligned along the X-direction by being affected by the hard bias layers
24
,
24
magnetized along the X-direction.
A static current (sensing current) is imparted from the lead layers
26
,
26
to the pinned magnetic layer
31
, non-magnetic conductive layer
32
and free magnetic layer
33
in this spin-valve type thin film element. Since the scanning direction of the recording medium such as a hard disk device is along the Z-direction, magnetization of the free magnetic layer turns from the X-direction to the Y-direction when the leakage magnetic field from the recording medium is applied along the Y-direction. Electric resistance varies depending on the relation between changes of the magnetization direction in the free magnetic layer
33
and the pinned magnetization direction of the pinned magnetic layer
31
. The leakage magnetic field from the recording medium is sensed due to voltage changes based on this electric resistance change.
Meanwhile, the film thickness of the leading layer
26
, formed on both side areas of the laminated body from the soft magnetic layer
20
through the protective layer
23
as shown in
FIG. 7A
, is very thick in order to reduce the direct current resistance (DCR) of the AMR element. Small direct current resistance allows the sensing output to be large, improving the regenerative characteristics.
However, the overall thickness of the both side areas comprising the hard bias layer
24
, interlayer
25
and lead layer
26
becomes thicker than the overall thickness of the laminated body (the layer from the soft magnetic layer
20
through the protective layer
23
) when the film thickness of the lead layer
26
is made thick, resulting in a distorted configuration of the top face of the AMR element as shown in FIG.
7
A.
Consequently, the bottom core layer
40
to be formed on the AMR element is deposited as a bent layer following the undulation of the top face of the AMR element as shown in
FIG. 7A
, also causing a distortion of the top core layer
41
in confronting relation over the bottom core layer
40
via a magnetic gap G.
When the portions of the bottom core layer
40
and top core layer
41
being in a confronting relation with each other via the magnetic gap G are distorted as shown in
FIG. 7A
, the recording patterns
42
,
43
written on the recording medium becomes non-linear as shown in
FIG. 7B
with bent portions at both ends. Non-linear recording of the signals on the recording medium as described above causes the following problems.
Supposing that the recording medium travels from the face to the back of the drawing to regenerate the signals in the recording pattern
42
, the signals in the recording pattern
43
outside of the signals in the recording pattern
42
are simultaneously regenerated at near the both end
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Cao Allen T.
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