U.S. patent application number 14/753301 was filed with the patent office on 2016-10-06 for magneto-resistive effect element with recessed antiferromagnetic layer.
The applicant listed for this patent is TDK Corporation. Invention is credited to Naomichi DEGAWA, Takayasu KANAYA, Kenzo MAKINO, Satoshi MIURA.
Application Number | 20160293188 14/753301 |
Document ID | / |
Family ID | 57016021 |
Filed Date | 2016-10-06 |
United States Patent
Application |
20160293188 |
Kind Code |
A1 |
DEGAWA; Naomichi ; et
al. |
October 6, 2016 |
MAGNETO-RESISTIVE EFFECT ELEMENT WITH RECESSED ANTIFERROMAGNETIC
LAYER
Abstract
A magneto-resistive effect element (MR element) has a first
shield layer; a second shield layer; an inner shield layer that is
positioned between the first shield layer and the second shield
layer, and that makes contact with the first shield layer and faces
the air bearing surface (ABS); and a multilayer film that is
positioned between the first shield layer and the second shield
layer. The multilayer film has a free layer; a first pinned layer;
a nonmagnetic spacer layer; a second pinned layer that fixes the
magnetization direction of the first pinned layer; and an
antiferromagnetic layer that is exchange-coupled with the second
pinned layer. The antiferromagnetic layer faces the back surface of
the inner shield layer viewed from the ABS. The MR element has an
insulating layer positioned between the antiferromagnetic layer and
the inner shield layer.
Inventors: |
DEGAWA; Naomichi; (Tokyo,
JP) ; MAKINO; Kenzo; (Tokyo, JP) ; MIURA;
Satoshi; (Tokyo, JP) ; KANAYA; Takayasu;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TDK Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
57016021 |
Appl. No.: |
14/753301 |
Filed: |
June 29, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14672693 |
Mar 30, 2015 |
|
|
|
14753301 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 33/098 20130101;
G11B 2005/3996 20130101; G11B 5/3912 20130101; G11B 5/3932
20130101 |
International
Class: |
G11B 5/39 20060101
G11B005/39; G11B 5/60 20060101 G11B005/60 |
Claims
1. A magneto-resistive effect element (MR element), comprising: a
first shield layer, a second shield layer, an inner shield layer
that is positioned between the first shield layer and the second
shield layer, that faces the first shield layer, and that faces an
air bearing surface (ABS), and a multilayer film that is positioned
between the first shield layer and the second shield layer, wherein
the multilayer film comprises a free layer having a magnetization
direction that fluctuates relative to an external magnetic field, a
first pinned layer that is positioned closer to the first shield
layer than the free layer, and having a magnetization direction
that is fixed relative to the external magnetic field, a
nonmagnetic spacer layer that is positioned between the free layer
and the first pinned layer, a second pinned layer that is
positioned closer to the first shield layer than the first pinned
layer, and that fixes the magnetization direction of the first
pinned layer, and an antiferromagnetic layer that is positioned
closer to the first shield layer than the second pinned layer, and
that is exchange-coupled with the second pinned layer; the
antiferromagnetic layer faces the back surface of the inner shield
layer viewed from the ABS; and the MR element comprises an
insulating layer between the antiferromagnetic layer and the inner
shield layer, wherein the second pinned layer comprises a first
part facing the back surface of the inner shield layer and a second
part that makes contact with the first part, and that extends to
the ABS between the first part and the first pinned layer and
between the inner shield layer and the first pinned layer, and the
insulating layer is positioned between the first part and the inner
shield layer, and between the antiferromagnetic layer and the inner
shield layer.
2. The MR element according to claim 1, wherein the insulating
layer is a nonmagnetic insulating layer.
3. (canceled)
4. The MR element according to claim 1, wherein the first part
comprises a first layer that makes contact with the
antiferromagnetic layer, a second layer that makes contact with the
second part, and a layer that is positioned between the first layer
and the second layer, and that generates-exchange coupling between
the first layer and the second layer.
5. The MR element according to claim 1, wherein the insulating
layer is made from aluminum oxide, silicon oxide, magnesium oxide,
nickel oxide, manganese oxide, tantalum oxide, cobalt oxide, iron
oxide or chrome oxide.
6. The MR element according to claim 1, comprising: a pair of bias
magnetic field application layers that are positioned at both sides
of the free layer in the cross track direction, and that include
respective soft magnetic layers, wherein the second shield layer
comprises: a soft magnetic layer, and an anisotropy application
layer that is positioned at an opposite side of the bias magnetic
field application layers across the soft magnetic layer of the
second shield layer, and that applies anisotropy to the soft
magnetic layer of the second shield layer; and the soft magnetic
layer of the bias magnetic field application layers are magnetized
to an orientation that is parallel or anti-parallel to the soft
magnetic layer of the second shield layer by the soft magnetic
layer of the second shield layer.
7. The MR element according to claim 6, wherein the anisotropy
application layer is made from an antiferromagnetic layer.
8. The MR element according to claim 6, wherein the anisotropy
application layer is made from a hard magnetic layer.
9. A head gimbal assembly (HGA), comprising: a magnetic head slider
including the MR element according to claim 1, and a suspension
that elastically supports the magnetic head slider, wherein the
suspension comprises: a flexure joined to the magnetic head slider,
a load beam having one end connected to the flexure, and a base
plate that is connected to the other end of the load beam.
10. A magnetic recording apparatus, comprising: a magnetic head
slider including the MR element according to claim 1, a magnetic
recording medium positioned opposite to the magnetic head slider, a
spindle motor that rotary-drives the magnetic recording medium, and
a device that supports the magnetic head slider, and that positions
the magnetic head slider relative to the magnetic recording
medium.
11. A magneto-resistive effect element (MR element), comprising: a
first shield layer, a second shield layer, an inner shield layer
that is positioned between the first shield layer and the second
shield layer, and that faces the first shield layer and faces an
air bearing surface (ABS), and a multilayer film that is positioned
between the first shield layer and the second shield layer, wherein
the multilayer film comprises: a free layer where its magnetization
direction fluctuates relative to an external magnetic field, a
first pinned layer that is positioned closer to the first shield
layer than the free layer, and having magnetization direction fixed
relative to the external magnetic field, a nonmagnetic spacer layer
that is positioned between the free layer and the first pinned
layer, a second pinned layer that is positioned closer to the first
shield layer than the first pinned layer, and that fixes the
magnetization direction of the first pinned layer, and an
antiferromagnetic layer that is positioned closer to the first
shield layer than the second pinned layer, and that is
exchange-coupled with the second pinned layer; the
antiferromagnetic layer faces the back surface of the inner shield
layer viewed from the ABS; and the MR element comprises a layer
that is positioned between the antiferromagnetic layer and the
inner shield layer, and that weakens exchange coupling between the
antiferromagnetic layer and the inner shield layer, wherein the
second pinned layer comprises a first part facing the back surface
of the inner shield layer and a second part that makes contact with
the first part, and that extends to the ABS between the first part
and the first pinned layer and between the inner shield layer and
the first pinned layer, and the layer that weakens the exchange
coupling between the antiferromagnetic layer and the inner shield
layer is positioned between the first part and the inner shield
layer, and between the antiferromagnetic layer and the inner shield
layer.
Description
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 14/672,693, filed Mar. 30, 2015.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a magneto-resistive effect
element (MR element), and it particularly relates to an MR element
where an antiferromagnetic layer that fixes a magnetization
direction of a pinned layer is recessed from the air bearing
surface (ABS).
[0004] 2. Description of the Related Art
[0005] A MR element has a multilayer film inducing a
magneto-resistive effect, and two magnetic shield layers between
which the multilayer film is disposed in the down track direction
(track circumferential direction or lamination direction of the
multilayer film). For the multilayer film, a spin-valve film is
commonly used. The spin-valve film has a free layer where its
magnetization direction is changed relative to an external magnetic
field, a first pinned layer where its magnetization direction is
fixed relative to the external magnetic field, and a spacer layer
positioned between the free layer and the first pinned layer. The
spacer layer is a nonmagnetic layer that generates a
magneto-resistive effect. The multilayer film further has a second
pinned layer that fixes the magnetization direction of the first
pinned layer and an antiferromagnetic layer that fixes the
magnetization of the second pinned layer. The gap between the two
magnetic shield layers is referred to as a read gap. In order to
enhance the recording density of the magnetic recording medium,
particularly the linear recording density, which is the recording
density in the down track direction, it is effective to reduce the
read gap.
[0006] U.S. Pat. No. 7,952,839 discloses an MR element that is
provided with an antiferromagnetic layer recessed from the air
bearing surface (ABS). The MR element has an inner shield layer
positioned between the two magnetic shield layers. The inner shield
layer is disposed on the magnetic shield layer adjacent to the
antiferromagnetic layer, and faces the ABS. A nonmagnetic
conductive layer (cap layer) facing the ABS is disposed between the
inner shield layer and the first pinned layer. The
antiferromagnetic layer makes contact with the back surface of the
inner shield layer viewed from the ABS, but does not face the ABS.
The second pinned layer is disposed on the antiferromagnetic layer,
and, similar to the antiferromagnetic layer, the second pinned
layer does not face the ABS. A portion of the first pinned layer
extends to the ABS on the nonmagnetic conductive layer.
[0007] U.S. Pat. No. 8,711,528 discloses an MR element where an
antiferromagnetic layer is recessed from an ABS. The MR element has
an inner shield layer positioned between two magnetic shield
layers. The inner shield layer is disposed on the magnetic shield
layer adjacent to the antiferromagnetic layer, and faces the ABS.
The second pinned layer and the first pinned layer extend to the
ABS on the magnetic shield layer.
[0008] In these MR elements, because the inner shield layer is
disposed on the ABS instead of the antiferromagnetic layer, it is
easy to reduce the read gap. Due to this, high-frequency
characteristics and bit error rate are also improved. Since the
antiferromagnetic layer is away from the ABS, it is difficult a
sense current to pass, and the thermostability of the
antiferromagnetic layer is improved. Since the antiferromagnetic
layer is away from the ABS, corrosion resistance of the
antiferromagnetic layer is also improved.
[0009] In general, in a spin-valve type MR element, the
magnetization direction of the first pinned layer is fixed to a
direction orthogonal to the ABS (hereinafter, referred to as the
height direction) regardless of the presence of an external
magnetic field. A pair of bias layers that apply a bias magnetic
field to the free layer are disposed on both sides of the free
layer in the cross track direction (the direction orthogonal to the
down track direction and the height direction), so as to allow the
magnetization direction of the free layer to be oriented in the
cross track direction. As a result, the magnetization direction of
the free layer is ideally orthogonal to the magnetization direction
of the first pinned layer when no external magnetic field exists.
When an external magnetic field is applied to the free layer, the
magnetization direction of the free layer rotates. The resistance
value of the sense current flowing in the multilayer film varies
according to the angle of rotation between the magnetization
direction of the free layer and that of the first pinned layer.
This is referred to as the magneto-resistive effect. Magnetic
information recorded in the magnetic recording medium is read based
on the magneto-resistive effect of the MR element.
[0010] In the MR element described in U.S. Pat. No. 7,952,839, the
antiferromagnetic layer makes contact with the inner shield layer,
and, in the MR element described in U.S. Pat. No. 8,711,528, the
antiferromagnetic layer is electrically connected to the inner
shield layer via a conductive seed layer. Consequently, the sense
current flowing in the inner shield layer flows in the
antiferromagnetic layer. Since the antiferromagnetic layer produces
heat by the applied current, the ratio of grains exceeding the
blocking temperature (temperature where the bias magnetic field
disappears) is increased. A force to fix the magnetization
direction of the second pinned layer by the antiferromagnetic layer
is weakened, and the magnetization direction of the second pinned
layer tends to rotate in the direction of the magnetic field to be
applied to the second pinned layer at the moment. As a result, the
magnetization direction of the first pinned layer tends to rotate,
and is no longer stable in the height direction. A shift of the
magnetization direction of the first pinned layer from the height
direction causes an increase in noise.
[0011] Therefore, the objective of the present invention is to
provide a magnetoresistive effect element (MR element) where an
antiferromagnetic layer is recessed from the air bearing surface
(ABS), and the magnetization direction of the antiferromagnetic
layer is stable.
SUMMARY OF THE INVENTION
[0012] The MR element of the present invention has a first shield
layer; a second shield layer; an inner shield layer that is
positioned between the first shield layer and the second shield
layer, that makes contact with the first shield layer and faces the
ABS; and a multilayer film that is positioned between the first
shield layer and the second shield layer. The multilayer film has a
free layer where its magnetization direction fluctuates relative to
the external magnetic field; a first pinned layer that is
positioned closer to the first shield layer than the free layer,
and where its magnetization direction is fixed relative to the
external magnetic field; a nonmagnetic spacer layer that is
positioned between the free layer and the first pinned layer; a
second pinned layer that is positioned closer to the first shield
layer than the first pinned layer; and an antiferromagnetic layer
that is positioned closer to the first shield layer than the second
pinned layer, and that is exchange-coupled with the second pinned
layer. The antiferromagnetic layer faces the back surface of the
inner shield layer viewed from the ABS. The MR element further has
an insulating layer that is positioned between the
antiferromagnetic layer and the inner shield layer.
[0013] The inner shield layer is electrically insulated from the
antiferromagnetic layer by the insulating layer. Consequently, it
becomes difficult for a current to flow from the inner shield layer
to the antiferromagnetic layer. Joule heat in the antiferromagnetic
layer is suppressed, and the magnetization directions of the first
pinned layer and the second pinned layer become stabilized.
[0014] The above-mentioned and other objectives, characteristics
and advantages become clear from the explanations below when
referring to the attached drawings illustrating the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a conceptual cross-sectional view of a magnetic
head slider relating to one embodiment of the present
invention;
[0016] FIG. 2 is a side view of a magneto-resistive effect element
viewed from Direction A in FIG. 1;
[0017] FIG. 3 is a cross-sectional view of the magneto-resistive
effect element viewed from the same direction as FIG. 1;
[0018] FIGS. 4A to 4E are conceptual diagrams explaining a method
for manufacturing a magneto-resistive effect element (MR
element);
[0019] FIG. 5 is a conceptual diagram showing a problem when there
is no nonmagnetic insulating layer;
[0020] FIG. 6 is a graph showing a relationship between the
magnetization direction of the inner shield layer and the position
of the free layer;
[0021] FIG. 7 is a graph showing a relationship between an output
of the magneto-resistive effect element and an offset distance of
an antiferromagnetic layer;
[0022] FIG. 8 is a graph showing a relationship between the
asymmetry of the magneto-resistive effect element and the offset
distance of the antiferromagnetic layer;
[0023] FIG. 9 is a cross-sectional view of the magneto-resistive
effect element relating to another embodiment of the present
invention;
[0024] FIG. 10 is a cross-sectional view of the magneto-resistive
effect element relating to another embodiment of the present
invention;
[0025] FIG. 11 is a side view of the magnetoresistive effect
element relating to another embodiment of the present
invention;
[0026] FIG. 12 is a perspective view of a head arm assembly of the
present invention;
[0027] FIG. 13 is a side view of a head stack assembly of the
present invention; and
[0028] FIG. 14 is a plan view of a magnetic recording
apparatus.
DETAILED DESCRIPTION OF THE INVENTION
[0029] A magneto-resistive effect element (MR element) relating to
the embodiments of the present invention, and embodiments of a
magnetic head slider using the MR element, are explained hereafter
with reference to the drawings.
[0030] FIG. 1 shows a main portion sectional view of a magnetic
head slider 1 relating to one embodiment of the present invention.
The magnetic head slider 1 has a substrate 6, a magneto-resistive
effect element (MR element) 2 formed over the substrate 6, and a
recording part 4 formed over the substrate 6. FIG. 2 is a side view
of the MR element 2 viewed from the direction A of FIG. 1, i.e.,
shows a configuration of the MR element 2 on the air bearing
surface S. FIG. 3 shows a cross-sectional view of the MR element 2
viewed from the same direction as FIG. 1. The air bearing surface S
is a surface opposite to a magnetic recording medium (hard disk) M
of the magnetic head slider 1. First, with reference to FIGS. 2 and
3, the configuration of the MR element 2 is explained.
[0031] The MR element 2 has a spin valve-type multilayer film 11; a
first shield layer 31 and second shield layer 33 that are
positioned at both sides of the multilayer film 11 relating to a
down track direction DT; and a pair of bias layers 36 that are
established at both sides of the multilayer film 11 relative to a
cross track direction CT. The multilayer film 11 is positioned
between the first shield layer 31 and the second shield layer 33.
The first shield layer 31 is closer to the substrate 6 than the
second shield layer 33.
[0032] The multilayer film 11 has a free layer 24 where its
magnetization direction varies relative to the external magnetic
field; a first pinned layer 22 where its magnetization direction is
fixed relative to the external magnetic field; and a spacer layer
23 that is positioned between the free layer 24 and the first
pinned layer 22. The free layer 24 and the first pinned layer 22
are made from CoFe, and may contain Ni. The free layer 24 and the
first pinned layer 22 may be made from a multilayer structure of
magnetic films such as CoFe, NiFe and CoFeB. Also, a nonmagnetic
layer may be included between these magnetic layers as long as the
nonmagnetic layer does not cut off the magnetic coupling. The
spacer layer 23 can be formed from various nonmagnetic layers that
attain magneto-resistive effects, such as copper, aluminum oxide,
gallium oxide, magnesium oxide or zinc oxide. A protective layer 25
for protecting the multilayer film 11 is formed between the free
layer 24 and the second shield layer 33. The protective layer 25 is
formed from a multilayer film made from Ta, Ru and the like.
[0033] Further, the multilayer film 11 has a second pinned layer 19
that is positioned closer to the first shield layer 31 than the
first pinned layer 22, and that fixes the magnetization direction
of the first pinned layer 22. The second pinned layer 19 is formed,
for example, from CoFe. A Ru layer 21 is disposed between the first
pinned layer 22 and the second pinned layer 19, and the first
pinned layer 22 and a second part 17 (described later) of the
second pinned layer 19 are exchange-coupled via the Ru layer
21.
[0034] The multilayer film 11 further has an antiferromagnetic
layer 13 that is positioned closer to the first shield layer 31
than the second pinned layer 19, and that is exchange-coupled with
the second pinned layer 19. The antiferromagnetic layer 13 faces
the back surface 32a of the inner shield layer 32 (described later)
viewed from the air bearing surface S, and is not on the air
bearing surface S. The antiferromagnetic layer 13 is formed from
IrMn. The antiferromagnetic layer 13 may be also formed from FeMn,
NiMn, PtMn or PdPtMn. The second pinned layer 19 makes contact with
the antiferromagnetic layer 13, and is magnetized in the height
direction HT. A seed layer 12 is disposed between the
antiferromagnetic layer 13 and the first shield layer 31. The seed
layer 12 is composed of a bilayer film with a Ru layer making
contact with the first shield layer 31 and a Ta layer making
contact with the antiferromagnetic layer 13. The seed layer 12 is
disposed in order to obtain excellent exchange coupling between the
antiferromagnetic layer 13 to be laminated onto it and the second
pinned layer 19.
[0035] The first shield layer 31 and the second shield layer 33 are
formed from, for example, NiFe (permalloy). The first shield layer
31 and the second shield layer 33 shield the external magnetic
field to be emitted from bits other than those subject to reading,
and allow the free layer 24 to detect only the magnetic field to be
emitted from the bits subject to reading.
[0036] The MR element 2 further has the inner shield layer 32. The
inner shield layer 32 is positioned between the first shield layer
31 and the second shield layer 33, and faces the air bearing
surface S. The inner shield layer 32 is formed from, for example,
NiFe, and makes contact with the first shield layer 31. Therefore,
the inner shield layer 32 functions as a magnetic shield of the
multilayer film 11 along with the first shield layer 31. A buffer
layer may be provided between the first shield layer 31 and the
inner shield layer 32. A read gap RG is regulated as the gap
between the inner shield layer 32 and the second shield layer 33.
In the MR element 2 of the present embodiment, the read gap RG is
reduced compared to a conventional MR element where the
antiferromagnetic layer 13 is positioned on the air bearing surface
S.
[0037] IrMn that configures the antiferromagnetic layer 13 tends to
be deteriorated by heat, and, the vicinity of the air bearing
surface S tends to be at a high temperature because of the flow of
the sense current. Since the antiferromagnetic layer 13 of the
present embodiment is recessed from the air bearing surface S, it
is difficult to be exposed to high temperature due to the electric
current. Further, the antiferromagnetic layer 13 tends to be
corroded if it faces the air bearing surface S. Since the
antiferromagnetic layer 13 of the present embodiment is protected
by the inner shield layer 32, the reliability of the MR element 2
is improved.
[0038] The inner shield layer 32 has a greater film thickness
(dimensions in the down track dimension DT) than the
antiferromagnetic layer 13. As a result, the second pinned layer 19
protrudes toward the first shield layer 31 or is depressed at a
position opposite to the antiferromagnetic layer 13. The second
pinned layer 19 has a first part 18, which is a protrusion part,
and a second part 17 with the shape of a flat film. The first part
18 faces the back surface 32a of the inner shield layer 32. The
second part 17 makes contact with the first part 18 in the down
track direction DT, and extends to the air bearing surface S
between the first part 18 and the first pinned layer 22, and
between the inner shield layer 32 and the first pinned layer 22.
The first part 18 is composed of a first layer 14, a Ru layer 15
and a second layer 16. The first layer 14 makes contact with the
antiferromagnetic layer 13, and is exchange-coupled with the
antiferromagnetic layer 13. The second layer 16 makes contact with
the second part 17, and is magnetically integrated with the second
part 17. The layer thickness of the Ru layer 15 is approximately
0.8 nm, and the magnetization direction of the second layer 16 is
fixed to an antiparallel orientation of the magnetization direction
of the first layer 14. Since the first part 18 has the first layer
14 and the second layer 16 that are magnetized in antiparallel
orientation with each other, the magnetic moment of the entire
first part 18 is suppressed.
[0039] A cap layer 35 is disposed between the second part 17 of the
second pinned layer 19 and the inner shield layer 32. The cap layer
35 is not particularly restricted as long as it is a nonmagnetic
metallic layer.
[0040] In the present embodiment, the cap layer 35 is composed of a
bilayer film with a Ta layer making contact with the inner shield
layer 32 and a Ru layer making contact with the second part 17 of
the second pinned layer 19.
[0041] A nonmagnetic insulating layer 34 is disposed between the
antiferromagnetic layer 13 and the inner shield layer 32, and
between the first part 18 of the second pinned layer 19 and the
inner shield layer 32. The nonmagnetic insulating layer 34 can be
formed from aluminum oxide, silicon oxide, magnesium oxide, nickel
oxide, manganese oxide, tantalum oxide, cobalt oxide, iron oxide or
chrome oxide. It is preferable that the film thickness of the
nonmagnetic insulating layer 34 is approximately 1 nm. The
nonmagnetic insulating layer 34 has two characteristics: it is both
"nonmagnetic" and "non-conductive".
[0042] Effects because the nonmagnetic insulating layer 34 is
"nonmagnetic" are as follows: The nonmagnetic insulating layer 34
shields or weakens magnetic coupling of the first portion 18 of the
second pinned layer 19 with the inner shield layer 32, and the
antiferromagnetic layer 13 with the inner shield layer 32. As
described later, it enables the magnetization directions of the
second pinned layer 19 and the first pinned layer 22 to be
stabilized. As a result of this, as described later with reference
to FIGS. 7 and 8, a variation of outputs relative to a change
(fluctuation) in offset distance D of the antiferromagnetic layer
13 from the back surface 24a of the free layer 24, and variations
of mean values of asymmetry, are suppressed.
[0043] Effects because of the nonmagnetic insulating layer 34 being
"non-conductive", i.e., having electric insulation properties, are
as follows:
[0044] (1) The occurrence of magnetic coupling based upon Ruderman
Kittel Kasuya Yosida (RKKY) interaction between the first part 18
of the second pinned layer 19 and the inner shield layer 32, or
between the antiferromagnetic layer 13 and the inner shield layer
32, is prevented. The RKKY interaction is one type of exchange
coupling, and it occurs when magnetic materials make contact with
each other via a metallic film. Therefore, the nonmagnetic
insulating layer 34 prevents the occurrence of the RKKY
interaction. It becomes difficult for the inner shield layer 32 to
be magnetized by the antiferromagnetic layer 13 due to this, as
well, and the magnetization directions of the second pinned layer
19 and the first pinned layer 22 are stabilized. As a result, as
described later with reference to FIGS. 7 and 8, a variation of
outputs relative to a change (fluctuation) in the offset distance D
of the antiferromagnetic layer 13 from the back surface 24a of the
free layer 24 and variations of mean values of asymmetry are
suppressed.
[0045] (2) The nonmagnetic insulating layer 34 prevents the sense
current flowing in the inner shield layer 32 from flowing (leaking)
into the antiferromagnetic layer 13. The antiferromagnetic layer 13
typified by IrMn generates heat because the sense current flows
through, and the temperature of the element exceeds the blocking
temperature of the grain. When the temperature of the element
exceeds the blocking temperature of the grain, a bias magnetic
field or their antiferromagnetic properties will be lost. As a
result, a force to fix the magnetization direction of the second
pinned layer 19 making contact with the antiferromagnetic layer 13
weakens. The magnetization direction of the second pinned layer 19
becomes susceptible to the external magnetic field, and the
magnetization direction that is ideally orientated toward the
height direction easily rotates to the cross track direction. As a
result, the magnetization direction of the first pinned layer 22
that is exchange-coupled with the second pinned layer 19 also
rotates to the same direction as the second pinned layer 19, and it
leads to an increase of noise of the MR element. The sense current
to be applied into the antiferromagnetic layer 13 is suppressed by
the nonmagnetic insulating layer 34, and noise of the MR element
can be suppressed.
[0046] Thus, the nonmagnetic insulating layer 34 of the present
embodiment has both "nonmagnetic" and "non-conductive"
charatceristics, but it may have only either one of the
characteristics. The nonmagnetic insulating layer 34 may be a
nonmagnetic layer or insulating non-conductive layer, and both
cases can provide the above effects.
[0047] With reference to FIG. 2, a pair of bias layers 36 is formed
from CoPt, CoCrPt or the like. Each bias magnetic field application
layer 36 applies a bias magnetic field to the free layer 24, and
magnetizes the free layer 24 into a single magnetic domain. When
there is no external magnetic field, the magnetization direction of
the free layer 24 is oriented toward the cross track direction CT
by the bias magnetic field. A pair of insulating layers 37 for
preventing bypass of the sense current are disposed between the
pair of the bias layers 36 and the multilayer film 11.
[0048] The first shield layer 31 and the second shield layer 33
also function as respective electrodes. Due to voltage to be
applied between the first shield layer 31 and the second shield
layer 33, the sense current flows into the multilayer film 11. When
the external magnetic field to be emitted from a magnetic recording
medium M is applied to the free layer 24, the magnetization
direction of the free layer 24 rotates to a predetermined direction
at a predetermined angle within the film surface of the free layer
24 according to the orientation and intensity of the external
magnetic field. The magnetization direction of the free layer 24
forms a relative angle according to the orientation and intensity
of the external magnetic field relative to the magnetization
direction of the first pinned layer 22, and spin-dependent
scattering of conductive electrons varies according to the relative
angle, and a magneto-resistive change occurs. A magnetic field from
the magnetic recording medium M at the position opposite to the
multilayer film 11 changes as the magnetic recording medium M
rotates. A change of the magnetic field is detected as a change of
electrical resistance of the sense current based upon the
magneto-resistive effect. The MR element 2 reads magnetic
information written into the magnetic recording medium M by
utilizing this principle.
[0049] The multilayer film 11 can be made using a conventional
method such as sputtering. A method for making the inner shield
layer 32, the antiferromagnetic layer 13, the second pinned layer
19, the nonmagnetic insulating layer 34 and the cap layer 35 is
described with reference to FIGS. 4A to 4E.
[0050] First, as shown in FIG. 4A, the first shield layer 31 is
made using a plating method, and the seed layer 12 (not shown), the
antiferromagnetic layer 13, and the first part 18 of the second
pinned layer 19 are sequentially formed on the first shield layer
31 using a sputtering method. Next, a photoresist 51 is made on the
first part 18 of the second pinned layer 19. The photoresist 51
will not be disposed in a region where the inner shield layer 32 is
made.
[0051] Next, as shown in FIG. 4B, the seed layer 12, the
antiferromagnetic layer 13 and the first part 18 of the second
pinned layer 19 are removed by ion milling. The portions of these
layers covered with the photoresist 51 are not removed. An ion beam
is applied from a direction that is nearly perpendicular to the
substrate 6 (down track direction DT). It is desirable that a side
surface 52 of the antiferromagnetic layer 13 and the first part 18
of the second pinned layer 19 formed by ion milling are slightly
inclined relative to an axis that is perpendicular to the substrate
6.
[0052] Next, as shown in FIG. 4C, a nonmagnetic insulating layer
53, which will become a nonmagnetic insulating layer 34, is formed
by sputtering. Slightly inclining the entering direction of ion
beam relative to an axis that is perpendicular to the substrate 6
enables a nonmagnetic insulating layer 53 to be formed also on the
side surface 52 of the antiferromagnetic layer 13 and the first
part 18 of the second pinned layer 19.
[0053] Next, as shown in FIG. 4D, the nonmagnetic insulating layer
53 deposited onto the first shield layer 31 is removed by ion
milling. The nonmagnetic insulating layer 53 deposited on the side
surface 52 of the antiferromagnetic layer 13 and the first portion
18 of the second pinned layer 19 is slightly thinned, and the
residual nonmagnetic insulating layer 53 becomes the nonmagnetic
insulating layer 34. Incidence of the ion beam from a direction
that is nearly perpendicular to the substrate 6 results in a
remaining portion of the film thickness of the nonmagnetic
insulating layer deposited onto the side surface 52 of the
antiferromagnetic layer 13 and the first part 18 of the second
pinned layer 19. Next, the inner shield layer 32 and the cap layer
35 are formed using a sputtering method. Since the nonmagnetic
insulating layer 34 deposited on the first shield layer 31 has been
removed in advance, the inner shield layer 32 makes contact with
the first shield layer 31, and is integrated with the first shield
layer 31. The buffer layer may be provided between the first shield
layer 31 and the inner shield layer 32.
[0054] Next, the photoresist 51 is removed as shown in FIG. 4E, and
a surface 54 of the cap layer 35 and the first part 18 of the
second pinned layer 19 are planarized by milling. Then, a second
part 17 of the second pinned layer 19 is formed on the cap layer 35
and the first part 18 of the second pinned layer 19 using a
sputtering method. The second part 17 of the second pinned layer 19
makes contact with a second layer 16 of the first part 18, and is
integrated with the second layer 16.
[0055] With reference to FIG. 1 again, the recording part 4 is
disposed above the multilayer film 11 via an interelement shield
layer 7 formed using a sputtering method. The recording part 4 has
a configuration for so-called perpendicular magnetic recording. A
magnetic pole layer for writing is composed of a main magnetic pole
layer 41 and an auxiliary magnetic pole layer 44. These magnetic
pole layers are formed using a frame plating method. The main
magnetic pole layer 41 is formed from an alloy made from any of two
or three of Ni, Fe and Co, and extends in the height direction HT.
A coil layer 45 extending on the gap layer 42 made from an
insulating material is wound around the main magnetic pole layer
41. The coil layer 45 is formed using a frame plating method.
Magnetic flux is induced to the main magnetic pole layer 41 by the
coil layer 45. This magnetic flux is guided inside the main
magnetic pole layer 41, and is emitted toward the magnetic
recording medium M from the air bearing surface S. The auxiliary
magnetic pole layer 44 is a magnetic layer that is magnetically
coupled with the main magnetic pole layer 41. The auxiliary
magnetic pole layer 44 is formed from an alloy made from any of two
or three of Ni, Fe and Co. The auxiliary magnetic pole layer 44 is
disposed by branching from the main magnetic pole layer 41, and is
opposite to the main magnetic pole layer 41 on the air bearing
surface S via the gap layer 42 and the coil insulating layer
43.
[0056] The free layer 24 and the first pinned layer 22 may be
disposed upside-down in the down track direction DT relating to the
spacer layer 23. Specifically, the free layer 24, the spacer layer
23, the first pinned layer 22, the second pinned layer 19 and the
antiferromagnetic layer 13 may be laminated in this order from the
first shield layer 31 toward the second shield layer 33. The inner
shield layer 32 makes contact with the second shield layer 33, and
the antiferromagnetic layer 13 is isolated from the air bearing
surface S via the inner shield layer 32.
[0057] FIG. 5 shows a side view of a magneto-resistive effect
element (MR element) 1002 where no nonmagnetic insulating layer 34
is disposed. When the inner shield layer 32 directly makes contact
with the antiferromagnetic layer 13 and the second pinned layer 19,
the inner shield layer 32 is exchange-coupled with the
antiferromagnetic layer 13, and is magnetized to the height
direction HT. The inner shield layer 32 is magnetized also by the
second pinned layer 19, and is further strongly magnetized in the
height direction HT. A magnetic field leaks from the magnetized
inner shield layer 32. This magnetic field leaks from the air
bearing surface S and the back surface 32a of the inner shield
layer 32 (Arrows F and G). The magnetic fields F and G that leak
from the inner shield layer 32 function so as to bend the
magnetization direction of the free layer 24 from the cross track
direction CT to the height direction HT. Consequently, the
magnetization direction of the free layer 24 rotates from the cross
track direction CT to the height direction HT under the situation
without an external magnetic field from the magnetic recording
medium M.
[0058] FIG. 6 is a graph where the magnetization directions of the
inner shield layer 32 are indicated as a function of the positions
of the free layer 24 in embodiments where the nonmagnetic
insulating layer 34 is disposed and in comparative examples where
no nonmagnetic insulating layer 34 is disposed. While a magnetic
recording medium with 2 bits that are magnetized in opposite
directions from each other was moved in the down track direction
DT, the magnetization direction of the inner shield layer 32 was
obtained by simulation. The horizontal axis indicates positions of
the free layer 24 in the down track direction DT, and the bit is
switched at "A". In other words, the external magnetic fields
emitted from the two bits offset each other at "A", and the
external magnetic field to be applied to the free layer 24 will
become zero. The vertical axis indicates the magnetization
direction of the inner shield layer 32. The angles: 0.degree. and
180.degree. indicate the cross track direction CT, and the angles:
90.degree. and 270.degree. indicate the height direction HT. The
magnetization direction of the inner shield layer 32 is orientated
toward the cross track direction CT by the bias magnetic field when
there is no external magnetic field, and the magnetization
direction is rotated in the height direction HT as the external
magnetic field increases (i.e., as separating from "A"), the
magnetization direction is rotated in the height direction HT. The
magnetization direction of the inner shield layer 32 is ideally
orientated toward 180.degree. under the situation without an
external magnetic field, and as the external magnetic field
increases, symmetrical behavior is demonstrated with 180.degree. as
a center. In the comparative example, the magnetization direction
of the inner shield layer 32 is in the vicinity of 185.degree. at
"A", and fluctuates between approximately 198.degree. and
approximately 172.degree. with the vicinity of 185.degree. as a
center. This indicates that the exchange coupling with the
antiferromagnetic layer 13 results in an application of a bias in
the magnetization direction of the inner shield layer 32, and in a
rotation of approximately 5.degree. relative to 180.degree., which
is the ideal magnetization direction. In the meantime, in the
embodiments, the exchange coupling between the inner shield layer
32 and the antiferromagnetic layer 13 is shielded by the
nonmagnetic insulating layer 34. The inner shield layer 32 receives
a magnetic field only from the bias magnetic field application
layer 36, and the magnetization direction without any external
magnetic field is oriented toward substantially 180.degree..
[0059] FIG. 7 is a graph showing a relationship between the offset
distance of the antiferromagnetic layer 13 from the back surface of
the free layer 24 and an output of the MR element 2. The horizontal
axis indicates the offset distance of the antiferromagnetic layer
13 from the back surface of the free layer 24. A side surface 13a
of the antiferromagnetic layer 13 is modeled as a parallel plane to
the air bearing surface S. As shown in FIG. 3, the offset distance
is defined as distance D in the height direction HT between the
side surface 13a of the antiferromagnetic layer 13 at the air
bearing surface S side and the back surface 24a of the free layer
24 at the opposite side from the air bearing surface S. The offset
distance D=0 indicates that the side surface 13a of the
antiferromagnetic layer 13 at the air bearing surface S side is
matched with the back surface 24a of the free layer 24. The right
side from "0" on the horizontal axis indicates that the
antiferromagnetic layer 13 is recessed from the back surface 24a of
the free layer 24. In the comparative example where no nonmagnetic
insulating layer 34 is disposed, variations of the outputs relative
to the change of the offset distance D are great. In the meantime,
in the embodiment where the antiferromagnetic insulating layer 34
is disposed, the variations of the outputs relative to the change
of the offset distance D are small.
[0060] FIG. 8 is a graph showing a relationship between the offset
distance D of the antiferromagnetic layer 13 from the back surface
24a of the free layer 24, and mean values for asymmetry. The
asymmetry is obtained with (A-B)/(A+B).times.100(%) when a height
(absolute value) of a vertex of the output voltage waveform at the
plus side is A and a height (absolute value) of the vertex at the
minus side is B. The mean value of the asymmetry is a value where
these asymmetries are averaged out relative to all vertices. The
horizontal axis, as similar to FIG. 7, indicates the offset
distance D of the side surface 13a of the antiferromagnetic layer
13 at the air bearing surface S side from the back surface 24a of
the free layer 24, and the vertical axis indicates the mean value
for the asymmetry. The shape of the antiferromagnetic layer 13 and
the definition of the offset distance D are the same as those in
FIG. 7. In the comparative example where no nonmagnetic insulating
layer 34 is disposed, variations of the mean values for the
asymmetries relative to the change of the offset distance D are
great. In the meantime, in the embodiment where the nonmagnetic
insulating layer 34 is disposed, the variations of the mean values
for asymmetry relative to the change of the offset distance D are
small. An absolute value of the mean values of asymmetry is also
greater in the present embodiment than that in the comparative
example.
[0061] Thus, disposing of the nonmagnetic insulating layer 34
between the antiferromagnetic layer 13 and the inner shield layer
32 results in reduction of a variation of outputs of the MR element
2 and reduction of a variation of mean values of asymmetry. The
disposing of the nonmagnetic insulating layer 34 results in
reduction of noise of the outputs ofthe MR element 2.
[0062] The cap layer 35 has an effect to suppress magnetic
magnetization of the inner shield layer 32 to the height direction
HT by the second part 17 of the second pinned layer 19. Since the
magnetization component of the inner shield layer 32 in the height
direction HT becomes smaller, a leakage magnetic field that enters
into the free layer 24 becomes smaller. Since the nonmagnetic
insulating layer 34 is disposed in the present embodiment, even if
insulation of the cap layer 35 is insufficient, magnetization of
the inner shield layer 32 can be suppressed. As a result, the film
thickness of the cap layer 35 can be reduced, and the film
thickness of the inner shield layer 32 can be increased. This
enables the further reduction of the read gap RG.
[0063] FIG. 9 is a similar diagram to FIG. 3 showing another
embodiment 102 of the MR element of the present invention. Elements
that are the same as those in the embodiment shown in FIG. 3 are
referenced with the same symbols in FIG. 3. In the present
embodiment, the first part 18 of the second pinned layer 19 has a
single layer configuration. In other words, the Ru layer 15 and the
second layer 16 are omitted. In the present embodiment, compared to
the embodiment shown in FIG. 3, the configuration of the second
pinned layer 19 and the manufacturing process thereof are
simplified.
[0064] FIG. 10 is a similar diagram to FIG. 3 showing another
embodiment 202 of the MR element of the present invention. Elements
that are the same as those in the embodiment shown in FIG. 3 are
referenced with the same symbols in FIG. 3. In the present
embodiment, the first part 18 of the second pinned layer 19 is not
disposed, and the second pinned layer 19 has a flat film shape as a
whole. In the present embodiment, the back surface 32a of the inner
shield layer 32 faces only the antiferromagnetic layer 13.
Therefore, the nonmagnetic insulating layer 34 is disposed only
between the antiferromagnetic layer 13 and the inner shield layer
32 except for the seed layer 12. In the present embodiment,
compared to the embodiment shown in FIG. 3, the configuration of
the second pinned layer 19 and the manufacturing process thereof
are simplified. Further, since the film thickness of the
antiferromagnetic layer 13 can be sufficiently secured, the
blocking temperature becomes higher and the thermal tolerability of
the antiferromagnetic layer 13 is improved. As a result, even if
the antiferromagnetic layer 13 reaches a high temperature because
of the leakage of the sense current into the antiferromagnetic
layer 13 or the like, the magnetization directions of the second
pinned layer 19 and the first pinned layer 22 are stabilized.
[0065] The film thickness of the inner shield layer 32 and that of
the antiferromagnetic layer 13 are not directly related, but these
can be independently determined, respectively. The inner shield
layer 32 can be determined according to necessary film thickness of
the second pinned layer 19, and it enables minimization of the read
gap RG. Therefore, in the embodiment shown in FIG. 3, it is easier
to reduce the read gap RG than the embodiments shown in FIGS. 9 and
10. Further, the Ru layer 15 functions as a protective film of the
antiferromagnetic layer 13 at the time of manufacturing, and
deterioration of the antiferromagnetic layer 13 can be prevented.
The antiferromagnetic layer 13 may protrude more toward the second
pinned layer 19 than the inner shield layer 32.
[0066] FIG. 11 is a similar diagram to FIG. 2 showing another
embodiment 302 of the MR element of the present invention. Elements
that are the same as those in the embodiment shown in FIG. 2 are
referenced with the same symbols in FIG. 2. The present embodiment
is characterized by the configuration of the second shield layer
133 and the bias magnetic field application layer 136, and it can
be combined with other embodiments described in the present
specification. The second shield layer 133 is composed of a soft
magnetic layer 61 and an anisotropy application layer 62 that
provides anisotropy to the soft magnetic layer 61. The anisotropy
application layer 62 is positioned at the opposite side of the bias
magnetic field application layer 136 across the soft magnetic layer
61. The soft magnetic layer 61 is formed from, for example, NiFe,
and the anisotropy application layer 62 can be formed from an
antiferromagnetic body, such as IrMn, PtMn, RuRhMn or FeMn. The
anisotropy application layer 62 can be formed from a hard magnetic
body, such as CoPT, CoCrPt or FePt. The soft magnetic layer 61 is
exchange-coupled with the anisotropy application layer 62, and is
magnetized in the cross track direction CT. At least a portion of
the bias magnetic field application layer 136 is formed from a soft
magnetic layer 63, for example, NiFe or the like. The soft magnetic
layer 63 of the bias magnetic field application layer 136 makes
contact with the soft magnetic layer 61 of the second shield layer
133, and is magnetized to the same orientation as the soft magnetic
layer 61 of the second shield layer 133. Consequently, the bias
magnetic field application layer 136 can apply a bias magnetic
field in the cross track direction CT to the free layer 24 as
similar to the bias magnetic field application layer 36 (see FIG.
2) composed of an antiferromagnetic material. The soft magnetic
layer 63 of the bias magnetic field application layer 136 may be
exchange-coupled with the soft magnetic layer 61 of the second
shield layer 133 via the Ru layer. This enables magnetization of
the soft magnetic layer 63 of the bias magnetic field application
layer 136 to be magnetized to an anti-parallel orientation with the
soft magnetic layer 61 of the second shield layer 133. Since the
bias magnetic field application layer 136 includes the soft
magnetic layer 63, it has an effect to shield a magnetic field
leaking from an adjacent track. Therefore, the effective track
width can be reduced, and a side lobe (a phenomenon where a local
maximum point of the output is generated at a position separated
from other than the track center in the cross track direction CT)
can be prevented at the same time. When the bias magnetic field
application layer 136 is formed from a soft magnetic material, it
may have a synthetic structure.
[0067] FIG. 12 is a perspective view of a head gimbal assembly
(HGA) 221.
The HGA 221 is provided with the magnetic head slider 1 where the
MR element 2 is mounted, and a suspension 220 that elastically
supports the magnetic head slider 1. The suspension 220 has a plate
spring-state load beam 222 formed from stainless steel, a flexure
223 disposed at one end part of the load beam 222, and a base plate
224 disposed at the other end part of the load beam 222. The
magnetic head slider 1 is joined to the flexure 223, and has a
moderate degree of freedom due to the flexure 223. A gimbal part
(not shown) to maintain the posture of the magnetic head slider 1
constant is disposed at a portion where the magnetic head slider 1
is attached to the flexure 223.
[0068] The HGA 221 is attached to the arm 230. The arm 230 moves
the magnetic head slider 1 in the cross track direction CT. The
base plate 224 is attached to one end of the arm 230. A coil 231
that is a portion of a voice coil motor is attached to the other
end part of the arm 230. A bearing 233 is disposed in the
intermediate part of the arm 230. The arm 230 is pivotably
supported by a shaft 234 mounted to the bearing 233. The arm 230
and the voice coil motor that drives the arm 230 configure an
actuator.
[0069] FIG. 13 is a side view of the head stack assembly 250. The
head stack assembly 250 has a carriage 251 having a plurality of
arms 230, and the HGAs 221 attached to each arm 230. The HGAs 221
are mounted to the arms 230 so as to align in the height direction
HT at intervals from each other. A pair of permanent magnets 232
are arranged at opposing positions across the coil 231.
[0070] FIG. 14 is a plan view of a magnetic recording apparatus.
The head stack assembly 250 is incorporated into a magnetic
recording apparatus 260. The magnetic recording apparatus 260 has a
plurality of magnetic recording media M attached to the spindle
motor 261. Two magnetic head sliders 1 opposite to each other
across the magnetic recording medium M are arranged in each
magnetic recording medium M.
The head stack assembly 250 except for the magnetic head sliders 1
and the actuator configure a positioning device, support the
magnetic head sliders 1, and position the magnetic head sliders
lrelative to the magnetic recording media M. The magnetic head
sliders 1 are moved in the cross track direction CT of the magnetic
recording media M by the actuator, and are positioned relative to
the magnetic recording media M, respectively. The magnetic head
sliders 1 record information into the magnetic recording media M by
the magnetic recording element, and reproduce the information
recorded in the magnetic recording media M by the MR element 2.
[0071] The preferred embodiments of the present invention were
presented and explained in detail, and please understand that these
are variously modifiable and correctable as long as not departing
from the concept or the scope of attached claims.
* * * * *