U.S. patent application number 16/271985 was filed with the patent office on 2019-06-06 for exchange-coupled film, magnetoresistive element including the same, and magnetic sensing device.
The applicant listed for this patent is ALPS ALPINE CO., LTD.. Invention is credited to Hiroaki ENDO, Fumihito KOIKE, Masamichi SAITO.
Application Number | 20190170835 16/271985 |
Document ID | / |
Family ID | 61161903 |
Filed Date | 2019-06-06 |
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United States Patent
Application |
20190170835 |
Kind Code |
A1 |
ENDO; Hiroaki ; et
al. |
June 6, 2019 |
EXCHANGE-COUPLED FILM, MAGNETORESISTIVE ELEMENT INCLUDING THE SAME,
AND MAGNETIC SENSING DEVICE
Abstract
An exchange-coupled film includes an antiferromagnetic layer,
pinned magnetic layer, and free magnetic layer which are stacked.
The antiferromagnetic layer is composed of a Pt--Cr sublayer and an
X--Mn sublayer (where X is Pt or Ir). The X--Mn sublayer is in
contact with the pinned magnetic layer.
Inventors: |
ENDO; Hiroaki; (Niigata-Ken,
JP) ; KOIKE; Fumihito; (Niigata-Ken, JP) ;
SAITO; Masamichi; (Niigata-Ken, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALPS ALPINE CO., LTD. |
Tokyo |
|
JP |
|
|
Family ID: |
61161903 |
Appl. No.: |
16/271985 |
Filed: |
February 11, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2017/009172 |
Mar 8, 2017 |
|
|
|
16271985 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B 5/3945 20130101;
G11B 2005/3996 20130101; H01F 10/12 20130101; H01L 43/08 20130101;
H01L 43/10 20130101; H01L 43/12 20130101; G01R 33/091 20130101;
G01R 33/007 20130101; G01R 33/0052 20130101; G01R 33/09 20130101;
H01F 10/3272 20130101; H01F 10/123 20130101; G11B 5/3906
20130101 |
International
Class: |
G01R 33/09 20060101
G01R033/09; H01F 10/32 20060101 H01F010/32 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2016 |
JP |
2016-157441 |
Claims
1. An exchange-coupled film comprising an antiferromagnetic layer
composed of a Pt--Cr sublayer and an X--Mn sublayer (where X is Pt
or Ir); and a pinned magnetic layer, the antiferromagnetic layer
and the pinned magnetic layer being stacked, wherein the X--Mn
sublayer of the antiferromagnetic layer is in contact with the
pinned magnetic layer.
2. The exchange-coupled film according to claim 1, wherein the
pinned magnetic layer is a self-pinned layer including a first
magnetic sublayer, intermediate sublayer, and second magnetic
sublayer which are stacked.
3. The exchange-coupled film according to claim 1, wherein the
thickness of the Pt--Cr sublayer is greater than the thickness of
the X--Mn sublayer.
4. The exchange-coupled film according to claim 3, wherein the
ratio of the thickness of the Pt--Cr sublayer to the thickness of
the X--Mn sublayer is 5:1 to 100:1.
5. The exchange-coupled film according to claim 1, wherein the
Pt--Cr sublayer has a composition represented by the formula
Pt.sub.XCr.sub.100 at %-X (X is 45 at % to 62 at %).
6. The exchange-coupled film according to claim 1, wherein the
Pt--Cr sublayer has a composition represented by the formula
Pt.sub.XCr.sub.100 at %-X (X is 50 at % to 57 at %).
7. The exchange-coupled film according to claim 1, further
comprising a base layer next to the antiferromagnetic layer,
wherein the base layer is made of Ni--Fe--Cr.
8. A magnetoresistive element comprising the exchange-coupled film
according to claim 1 and a free magnetic layer, the
exchange-coupled film and the free magnetic layer being
stacked.
9. A magnetic sensing device comprising the magnetoresistive
element according to claim 8.
10. The magnetic sensing device according to claim 9, further
comprising a plurality of magnetoresistive elements, placed on a
single substrate, identical to the magnetoresistive element
according to claim 8, wherein the magnetoresistive elements include
those having different pinned magnetization directions.
11. A method for manufacturing the exchange-coupled film according
to claim 1, comprising forming the Pt--Cr sublayer by a process for
co-sputtering Pt and Cr.
Description
CLAIM OF PRIORITY
[0001] This application is a Continuation of International
Application No. PCT/JP2017/009172 filed on Mar. 8, 2017, which
claims benefit of Japanese Patent Application No. 2016-157441 filed
on Aug. 10, 2016. The entire contents of each application noted
above are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to an exchange-coupled film, a
magnetoresistive element including the same, and a magnetic sensing
device.
2. Description of the Related Art
[0003] Exchange-coupled films including an antiferromagnetic layer
and a pinned magnetic layer are used as magnetoresistive elements
or magnetic sensing devices. Japanese Unexamined Patent Application
Publication No. 2000-215431 (hereinafter referred to as the patent
document) describes that in a magnetic recording medium, an
exchange-coupled film can be configured by combining a Co alloy
serving as a ferromagnetic film with various alloys serving as
antiferromagnetic films. As antiferromagnetic films, alloys such as
Co--Mn, Ni--Mn, Pt--Mn, and Pt--Cr are exemplified.
[0004] A magnetic sensing device requires solder reflowing
(melting) when a magnetoresistive element is mounted on a board.
The magnetic sensing device is used in a high-temperature
environment such as the vicinity of an engine in some cases.
Therefore, an exchange-coupled film for use in the magnetic sensing
device preferably exhibits such a high magnetic field (Hex) that
the magnetization direction of a pinned magnetic layer is reversed
and also exhibits high stability under high-temperature conditions
for the purpose of enabling a magnetic field to be detected in a
wide dynamic range.
[0005] The patent document relates to an exchange-coupled film used
as a magnetic recording medium and therefore does not describe the
stability of a magnetic sensing device including an
exchange-coupled film under high-temperature conditions. Although
the patent document exemplifies Pt--Cr as an antiferromagnetic
film, the patent document does not describe that composing Pt--Cr
at what composition ratio is preferable.
SUMMARY OF THE INVENTION
[0006] The present invention provides an exchange-coupled film
which exhibits such a high magnetic field (Hex) that the
magnetization direction of a pinned magnetic layer is reversed and
which exhibits high stability under high-temperature conditions, a
magnetoresistive element including the same, and a magnetic sensing
device.
[0007] An exchange-coupled film according to the present invention
includes an antiferromagnetic layer and pinned magnetic layer which
are stacked. The antiferromagnetic layer is composed of a Pt--Cr
sublayer and X--Mn sublayer (where, X is Pt or Ir). The X--Mn
sublayer is in contact with the pinned magnetic layer.
[0008] The pinned magnetic layer may be a self-pinned layer
including a first magnetic sublayer, intermediate sublayer, and
second magnetic sublayer which are stacked.
[0009] The thickness of the Pt--Cr sublayer is preferably greater
than the thickness of the X--Mn sublayer.
[0010] The ratio of the thickness of the Pt--Cr sublayer to the
thickness of the X--Mn sublayer is preferably 5:1 to 100:1.
[0011] The Pt--Cr sublayer preferably has a composition represented
by the formula Pt.sub.XCr.sub.100 at %-X (X is 45 at % to 62 at %)
and more preferably a composition represented by the formula
Pt.sub.XCr.sub.100 at %-x (X is 50 at % to 57 at %).
[0012] The exchange-coupled film preferably includes a base layer
next to the antiferromagnetic layer. The base layer is preferably
made of Ni--Fe--Cr.
[0013] A magnetoresistive element according to the present
invention includes the exchange-coupled film according to the
present invention and a free magnetic layer, the exchange-coupled
film and the free magnetic layer being stacked.
[0014] A magnetic sensing device according to the present invention
includes the magnetoresistive element according to the present
invention.
[0015] The magnetic sensing device according the present invention
includes a plurality of magnetoresistive elements, placed on a
single substrate, identical to the magnetoresistive element
according to the present invention. The magnetoresistive elements
include those having different pinned magnetization directions.
[0016] A method for manufacturing an exchange-coupled film
according to the present invention includes forming a Pt--Cr
sublayer by a process for co-sputtering Pt and Cr.
[0017] An exchange-coupled film according to the present invention
includes an antiferromagnetic layer composed of a Pt--Cr sublayer
and an X--Mn sublayer (where X is Pt or Ir) and therefore exhibits
such a high magnetic field (Hex) that the magnetization direction
of a pinned magnetic layer is reversed is high and increased
stability under high-temperature conditions. Thus, using the
exchange-coupled film according to the present invention enables a
magnetic sensing device which is stable even if the magnetic
sensing device is reflowed at high temperature or is used in a
high-temperature environment to be obtained.
[0018] In accordance with a manufacturing method according to the
present invention, an exchange-coupled film including a pinned
magnetic layer with high Hex can be manufactured by co-sputtering
Pt and Cr.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is an illustration showing the film configuration of
an exchange-coupled film according to a first embodiment of the
present invention;
[0020] FIG. 2 is an illustration showing the film configuration of
an exchange-coupled film according to a second embodiment of the
present invention;
[0021] FIG. 3 is a circuit block diagram of a magnetic sensor
according to an embodiment of the present invention;
[0022] FIG. 4 is a plan view showing magnetic sensing elements 11
used in the magnetic sensor;
[0023] FIG. 5 is a graph showing R--H curves of a magnetic sensing
element prepared in Example 1;
[0024] FIG. 6 is a graph showing R--H curves of a magnetic sensing
element prepared in Example 2;
[0025] FIG. 7 is a graph showing R--H curves of a magnetic sensing
element prepared in Comparative Example 1;
[0026] FIG. 8 is a graph showing the Hex of each of
exchange-coupled films prepared in Examples 3 to 5;
[0027] FIG. 9 is a graph showing the Hex of each of
exchange-coupled films prepared in Example 6;
[0028] FIGS. 10A to 10C are graphs showing R--H curves of a
magnetic sensing element prepared in Example 7;
[0029] FIGS. 11A to 11C are graphs showing R--H curves of a
magnetic sensing element prepared in Example 8;
[0030] FIGS. 12A to 12C are graphs showing R--H curves of a
magnetic sensing element prepared in Comparative Example 2;
[0031] FIG. 13 is a graph showing the relationship between the
percentage of Pt contained in Pt--Cr prepared in each of Reference
Example 1 and Reference Example 2 and the Hex;
[0032] FIG. 14 is a graph showing the relationship between the
percentage of Pt contained in Pt--Cr prepared in each of Reference
Example 1 and Reference Example 3 and the Hex;
[0033] FIG. 15 is an illustration showing the film configuration of
an exchange-coupled film prepared in each of Examples 9 to 12 and
Comparative Examples 3 and 4; and
[0034] FIG. 16 is a graph showing the relationship between the
temperature of an exchange-coupled film prepared in each of
Examples 9 to 12 and Comparative Examples 3 and 4 and the Hex.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0035] FIG. 1 shows the film configuration of a magnetic sensing
element 11 including an exchange-coupled film 10 according to a
first embodiment of the present invention.
[0036] The magnetic sensing element 11 is formed by stacking a base
layer 1, an antiferromagnetic layer 2, a pinned magnetic layer 3,
an nonmagnetic material layer 4, a free magnetic layer 5, and a
protective layer 6 in that order from a surface of a substrate. The
antiferromagnetic layer 2 is composed of a Pt--Cr sublayer 2A and
an X--Mn sublayer 2B (where, X is Pt or Ir). The X--Mn sublayer 2B
is in contact with the pinned magnetic layer 3. These layers are
formed by, for example, a sputtering process or a CVD process. The
base layer 1 and the pinned magnetic layer 3 form the
exchange-coupled film 10.
[0037] The magnetic sensing element 11 is a multilayer element
using a so-called single spin valve type of giant magnetoresistive
effect (GMR effect) and the electrical resistance thereof varies
depending on the relative relation between the vector of the pinned
magnetization of the pinned magnetic layer 3 and the vector of
magnetization that varies depending on the external magnetic field
of the free magnetic layer 5.
[0038] The base layer 1 is formed from a Ni--Fe--Cr alloy
(nickel-iron-chromium alloy), Cr, Ta, or the like. In the
exchange-coupled film 10, the Ni--Fe--Cr alloy is preferable for
the purpose of increasing the magnetic field (hereinafter also
appropriately referred to as the "Hex") at which the magnetization
of the pinned magnetic layer 3 is reversed.
[0039] The antiferromagnetic layer 2 has a multilayer structure
composed of the Pt--Cr sublayer 2A and the X--Mn sublayer 2B
(where, X is Pt or Ir). In order to increase the Hex, the thickness
D1 of the Pt--Cr sublayer 2A is preferably greater than the
thickness D2 of the X--Mn sublayer 2B. The ratio of the thickness
D1 to the thickness D2 (D1:D2) is preferably 5:1 to 100:1 and more
preferably 10:1 to 50:1.
[0040] From the viewpoint of increasing the Hex, the Pt--Cr
sublayer 2A preferably has a composition represented by the formula
Pt.sub.XCr.sub.100 at %-X (X is 45 at % to 62 at %) and more
preferably a composition represented by the formula
Pt.sub.XCr.sub.100 at %-X (X is 50 at % to 57 at %). From the same
viewpoint, the X--Mn sublayer 2B is preferably a Pt--Mn
sublayer.
[0041] In this embodiment, the antiferromagnetic layer 2 is
regularized by annealing, whereby exchange coupling is induced
between (at the interface between) the antiferromagnetic layer 2
and the pinned magnetic layer 3. The exchange coupling increases
the strong-magnetic field resistance of the pinned magnetic layer 3
to increase the Hex.
[0042] The pinned magnetic layer 3 is formed from a Co--Fe alloy
(cobalt-iron alloy). Increasing the content of Fe in the Co--Fe
alloy increases the coercive force thereof. The pinned magnetic
layer 3 is a layer contributing to the spin valve type of giant
magnetoresistive effect. A direction in which the pinned
magnetization direction P of the pinned magnetic layer 3 extends is
the sensitivity axis direction of the magnetic sensing element
11.
[0043] The nonmagnetic material layer 4 can be formed using Cu
(copper) or the like.
[0044] The free magnetic layer 5 is not limited in material or
structure. The free magnetic layer 5 can be formed using, for
example, material such as a Co--Fe alloy (cobalt-iron alloy) or a
Ni--Fe alloy (nickel-iron alloy) in the form of a single-layer
structure, a multilayer structure, or a multilayered ferrimagnetic
structure.
[0045] The protective layer 6 can be formed using Ta
(tantalum).
Second Embodiment
[0046] FIG. 2 is an illustration showing the film configuration of
a magnetic sensing element 21 including an exchange-coupled film 20
according to a second embodiment of the present invention. In this
embodiment, layers having the same function as that of the magnetic
sensing element 11 shown in FIG. 1 are given the same reference
numerals and will not be described in detail.
[0047] In the magnetic sensing element 21, the exchange-coupled
film 20 is composed of a pinned magnetic layer 3 with a self-pinned
structure and an antiferromagnetic layer 2 joined thereto. The
magnetic sensing element 21 differs from the magnetic sensing
element 11 shown in FIG. 1 in that a nonmagnetic material layer 4
and a free magnetic layer 5 are placed under the pinned magnetic
layer 3.
[0048] The magnetic sensing element 21 is also a multilayer element
using a so-called single spin valve type of giant magnetoresistive
effect. The electrical resistance thereof varies depending on the
relative relation between the vector of the pinned magnetization of
a first magnetic sublayer 3A of the pinned magnetic layer 3 and the
vector of magnetization that varies depending on the external
magnetic field of the free magnetic layer 5.
[0049] The pinned magnetic layer 3 has a self-pinned structure
composed of the first magnetic sublayer 3A, a second magnetic
sublayer 3C, and a nonmagnetic intermediate sublayer 3B located
between these two sublayers. The pinned magnetization direction P1
of the first magnetic sublayer 3A is antiparallel to the pinned
magnetization direction P2 of the second magnetic sublayer 3C
because of interaction. The first magnetic sublayer 3A is next to
the nonmagnetic material layer 4 and the pinned magnetization
direction P1 of the first magnetic sublayer 3A is the pinned
magnetization direction of the pinned magnetic layer 3. A direction
in which the pinned magnetization direction P1 extends is the
sensitivity axis direction of the magnetic sensing element 21.
[0050] The first magnetic sublayer 3A and the second magnetic
sublayer 3C are formed from an Fe--Co alloy (iron-cobalt alloy).
Increasing the content of Fe in the Fe--Co alloy increases the
coercive force thereof. The first magnetic sublayer 3A, which is
next to the nonmagnetic material layer 4, is a layer contributing
to the spin valve type of giant magnetoresistive effect.
[0051] The nonmagnetic intermediate sublayer 3B is formed from Ru
(ruthenium) or the like. The nonmagnetic intermediate sublayer 3B,
which is made of Ru, preferably has a thickness of 3 .ANG. to 5
.ANG. or 8 .ANG. to 10 .ANG..
Configuration of Magnetic Sensor
[0052] FIG. 3 shows a magnetic sensor (magnetic sensing device) 30
including a plurality of magnetic sensing elements identical to the
magnetic sensing element 11 shown in FIG. 1.
[0053] Referring to FIG. 3, the magnetic sensing elements are
different in pinned magnetization direction P (refer to FIG. 1) and
are given different reference numerals 11Xa, 11Xb, 11Ya, and 11Yb
for discrimination purposes. In the magnetic sensor 30, the
magnetic sensing elements 11Xa, 11Xb, 11Ya, and 11Yb are placed on
a single substrate.
[0054] As shown in FIG. 3, the magnetic sensor 30 includes a full
bridge circuit 32X and a full bridge circuit 32Y. The full bridge
circuit 32X includes the two magnetic sensing elements 11Xa and the
two magnetic sensing elements 11Xb. The full bridge circuit 32Y
includes the two magnetic sensing elements 11Ya and two magnetic
sensing elements 11Yb. The magnetic sensing elements 11Xa, 11Xb,
11Ya, and 11Yb have the film structure of the exchange-coupled film
10 of the magnetic sensing element 11 shown in FIG. 1. These are
hereinafter appropriately referred to as the magnetic sensing
elements 11 unless these are discriminated.
[0055] The full bridge circuit 32X and the full bridge circuit 32Y
include the magnetic sensing elements 11 having different pinned
magnetization directions indicated by arrows as shown in FIG. 3 for
the purpose of allowing detected magnetic field directions to
differ and have the same mechanism for detecting a magnetic field.
A mechanism for detecting a magnetic field using the full bridge
circuit 32X is described below.
[0056] The full bridge circuit 32X is composed of a first series
section 32Xa and second series section 32Xb connected in series to
each other. The first series section 32Xa is composed of the
magnetic sensing elements 11Xa and 11Xb connected in series to each
other. The second series section 32Xb is composed of the magnetic
sensing elements 11Xb and 11Xa connected in series to each
other.
[0057] A power-supply voltage Vdd is applied to a power-supply
terminal 33 common to the magnetic sensing element 11Xa included in
the first series section 32Xa and the magnetic sensing element 11Xb
included in the second series section 32Xb. A ground terminal 34
common to the magnetic sensing element 11Xb included in the first
series section 32Xa and the magnetic sensing element 11Xa included
in the second series section 32Xb is set to the ground potential
GND.
[0058] The differential output (OutX1)-(OutX2) between the output
potential (OutX1) of the midpoint 35Xa of the first series section
32Xa and the output potential (OutX2) of the midpoint 35Xb of the
second series section 32Xb is obtained as a detection output
(detection output voltage) VXs in an X-direction.
[0059] The full bridge circuit 32Y works similarly to the full
bridge circuit 32X and therefore the differential output
(OutY1)-(OutY2) between the output potential (OutY1) of the
midpoint 35Ya of a first series section 32Ya included in the full
bridge circuit 32Y and the output potential (OutY2) of the midpoint
35Yb of a second series section 32Yb included in the full bridge
circuit 32Y is obtained as a detection output (detection output
voltage) VYs in a Y-direction.
[0060] As indicated by arrows in FIG. 3, the sensitivity axis
direction of each of the magnetic sensing elements 11Xa and 11Xb
forming the full bridge circuit 32X is perpendicular to the
sensitivity axis direction of each of the magnetic sensing elements
11Ya and 11Yb forming the full bridge circuit 32Y.
[0061] As shown in FIG. 3, in the magnetic sensor 30, the
orientation of the free magnetic layer 5 of each magnetic sensing
element 11 varies so as to follow the direction of an external
magnetic field H. In this event, the resistance varies depending on
the vector relationship between the pinned magnetization direction
P of the pinned magnetic layer 3 and the magnetization direction of
the free magnetic layer 5.
[0062] Supposing that, for example, the external magnetic field H
acts in a direction shown in FIG. 3. The magnetic sensing element
11Xa included in the full bridge circuit 32X exhibits a reduced
electrical resistance because the sensitivity axis direction
coincides with the direction of the external magnetic field H.
However, the magnetic sensing element 11Xb exhibits an increased
electrical resistance because the sensitivity axis direction is
opposite to the direction of the external magnetic field H. The
change of the electrical resistance allows the detection output
voltage VXs=(OutX1)-(OutX2) to peak. As the external magnetic field
H changes rightward with respect to the plane of FIG. 3, the
detection output voltage VXs decreases. As the external magnetic
field H changes upward or downward with respect to the plane of
FIG. 3, the detection output voltage VXs decreases to zero.
[0063] On the other hand, in the full bridge circuit 32Y, when the
external magnetic field H is leftward with respect to the plane of
FIG. 3, the magnetization direction of the free magnetic layer 5 of
every magnetic sensing element 11 is perpendicular to the
sensitivity axis direction (pinned magnetization direction P) and
therefore the magnetic sensing elements 11Ya and 11Xb exhibit the
same resistance. Thus, the detection output voltage VYs is zero.
When the external magnetic field H acts downward with respect to
the plane of FIG. 3, the detection output voltage
VYs=(OutY1)-(OutY2) of the full bridge circuit 32Y peaks. As the
external magnetic field H changes upward with respect to the plane
thereof, the detection output voltage VYs decreases.
[0064] As described above, as the direction of the external
magnetic field H changes, the detection output voltage VXs of the
full bridge circuit 32X and the detection output voltage VYs of the
full bridge circuit 32Y vary. Thus, the movement direction and
travel distance (relative position) of a detection target can be
detected on the basis of the detection output voltages VXs and VYs
obtained from the full bridge circuits 32X and 32Y.
[0065] FIG. 3 shows the magnetic sensor 30, which is configured to
be capable of detecting a magnetic field in the X-direction and a
Y-direction perpendicular to the X-direction. However, the magnetic
sensor 30 may be configured to include the full bridge circuit 32X
or the full bridge circuit 32Y only so as to detect a magnetic
field in the X-direction or the Y-direction, respectively,
only.
[0066] FIG. 4 shows the planar structure of each of the magnetic
sensing elements 11Xa and 11Xb. In FIGS. 3 and 4, a BXa-BXb
direction is the X-direction. In FIG. 4, (A) and (B) show the
pinned magnetization directions P of the magnetic sensing elements
11Xa and 11Xb as indicated by arrows. The pinned magnetization
directions P of the magnetic sensing elements 11Xa and 11Xb are the
X-direction and are opposite to each other.
[0067] As shown in FIG. 4, the magnetic sensing elements 11Xa and
11Xb each include stripe-shaped element sections 12. The
longitudinal direction of each element section 12 is directed in a
BYa-BYb direction. A plurality of the element sections 12 are
placed in parallel to each other. Illustrated right end portions of
the neighboring element sections 12 are connected to each other
with conductive sections 13a. Illustrated left end portions of the
neighboring element sections 12 are connected to each other with
conductive sections 13b. The conductive sections 13a and 13b are
alternately connected to the illustrated right and left end
portions of the element sections 12, whereby the element sections
12 are coupled to each other in a so-called meander pattern. In the
magnetic sensing elements 11Xa and 11Xb, the conductive section 13a
shown in a lower right portion is united with a connection terminal
14a and the conductive section 13b shown in an upper left portion
is united with a connection terminal 14b.
[0068] Each element section 12 is composed of a plurality of
stacked metal layers (alloy layers). FIG. 1 shows the multilayer
structure of the element section 12. The element section 12 may
have a multilayer structure shown in FIG. 2.
[0069] In the magnetic sensor 30 shown in FIGS. 3 and 4, the
magnetic sensing element 11 can be replaced with the magnetic
sensing element 21, shown in FIG. 2, according to the second
embodiment.
EXAMPLES
Example 1
[0070] A magnetic sensing element 11 (refer to FIG. 1) including an
exchange-coupled film 10 having a film configuration below was
prepared. In examples, comparative examples, and reference examples
below, a parenthesized value is a thickness (.ANG.). The
exchange-coupled film 10 was annealed at 400.degree. C. for 5 hours
in a magnetic field of 1 kOe, whereby the magnetization of each of
a pinned magnetic layer 3 and an antiferromagnetic layer 2 was
pinned.
[0071] Substrate/base layer 1: Ni--Fe--Cr (60)/antiferromagnetic
layer 2 [Pt--Cr sublayer 2A: Pt.sub.51 at %-Cr.sub.49 at %
(280)/X--Mn sublayer 2B: Pt.sub.50 at %-Mn.sub.50 at % (20)]/pinned
magnetic layer 3: Co.sub.90 at %-Fe.sub.10 at % (50)/nonmagnetic
material layer 4: Cu (40)/free magnetic layer 5: Co.sub.90 at
%-Fe.sub.10 at % (15)/Ni.sub.81.5 at %-Fe.sub.18.5 at %
(30)/protective layer 6: Ta (50)
Example 2
[0072] A magnetic sensing element 11 including an exchange-coupled
film 10 having a film configuration below was prepared by changing
a Pt--Cr sublayer 2A of an antiferromagnetic layer 2 from Pt.sub.51
at %-Cr.sub.49 at % (280) prepared in Example 1 to Pt.sub.54 at
%-Cr.sub.46 at % (280).
[0073] Substrate/base layer 1: Ni--Fe--Cr (60)/antiferromagnetic
layer 2 [Pt--Cr sublayer 2A: Pt.sub.54 at %-Cr.sub.46 at %
(280)/X--Mn sublayer 2B: Pt.sub.50 at %-Mn.sub.50 at % (20)]/pinned
magnetic layer 3: Co.sub.90 at %-Fe.sub.10 at % (50)/nonmagnetic
material layer 4: Cu (40)/free magnetic layer 5: Co.sub.90 at
%-Fe.sub.10 at % (15)/Ni.sub.81.5 at %-Fe.sub.18.5 at %
(30)/protective layer 6: Ta (50)
Comparative Example 1
[0074] A magnetic sensing element 11 including an exchange-coupled
film 10 having a film configuration below was prepared by changing
an antiferromagnetic layer 2 from [Pt--Cr sublayer 2A: Pt.sub.51 at
%-Cr.sub.49 at % (280)/X--Mn sublayer 2B: Pt.sub.50 at %-Mn.sub.50
at % (20)] prepared in Example 1 to Pt.sub.50 at %-Mn.sub.50 at %
(300).
[0075] Substrate/base layer 1: Ni--Fe--Cr (60)/antiferromagnetic
layer 2: Pt.sub.50 at %-Mn.sub.50 at % (300)/pinned magnetic layer
3: Co.sub.90 at %-Fe.sub.10 at % (50)/nonmagnetic material layer 4:
Cu (40)/free magnetic layer 5: Co.sub.90 at %-Fe.sub.10 at %
(15)/Ni.sub.81.5 at %-Fe.sub.18.5 at % (30)/protective layer 6: Ta
(50)
Application of External Magnetic Field
[0076] An external magnetic field H was applied to the magnetic
sensing element 11 prepared in each of Example 1, Example 2, and
Comparative Example 1 from a direction parallel to the pinned
magnetization direction (a P-direction in FIG. 1) of the pinned
magnetic layer 3 of the exchange-coupled film 10, whereby the rate
(rate of change in resistance) .DELTA.MR (.DELTA.R/R) at which the
electrical resistance R was changed by the magnetic field H was
determined.
[0077] FIG. 5, FIG. 6, and FIG. 7 show R--H curves of the magnetic
sensing element 11 prepared in Example 1, R--H curves of the
magnetic sensing element 11 prepared in Example 2, and R--H curves
of the magnetic sensing element 11 prepared in Comparative Example
1, respectively. In each of these figures, the horizontal axis
represents the intensity [Oe] of the magnetic field H, the vertical
axis represents the rate of change in resistance .DELTA.MR [%], a
curve (a curve located on a lower side at H=1,000 [Oe]) marked
"Inc." represents .DELTA.MR in the case of increasing the magnetic
field H, and a curve (a curve located on an upper side at H=1,000
[Oe]) marked "Dec." represents .DELTA.MR in the case of reducing
the magnetic field H.
[0078] Referring to FIGS. 5 to 7, hysteresis appears in the
variation curve "Inc." of the rate of change in resistance
.DELTA.MR [o] in the case of changing the magnetic field to a
positive side and the variation curve "Dec." of the rate of change
in resistance .DELTA.MR [o] in the case of changing the magnetic
field to a negative side and the median of the full width at half
maximum of each of the variation curve "Inc." and the variation
curve "Dec." substantially coincides with the magnetic field (Hex)
at which the magnetization direction of a pinned magnetic layer is
reversed.
[0079] It was clear that the magnetic sensing element 11 prepared
in Example 1 and the magnetic sensing element 11 prepared in
Example 2 exhibited a higher magnetic field (Hex) as compared to
the magnetic sensing element 11 prepared in Comparative Example 1.
That is, the magnetic sensing elements 11 including the
exchange-coupled films 10 prepared in Examples 1 and 2 can
sufficiently measure a magnetic field in a strong-magnetic field
environment.
Example 3
[0080] Exchange-coupled films 10 (refer to FIG. 1) having a film
configuration below were prepared by varying the thickness D1 of a
Pt--Cr sublayer 2A of an antiferromagnetic layer 2 and the
thickness D2 of a Pt--Mn sublayer 2B thereof. The exchange-coupled
films 10 were annealed at 400.degree. C. for 5 hours in a magnetic
field of 1 kOe, whereby the magnetization of each of a pinned
magnetic layer 3 and the antiferromagnetic layer 2 was pinned.
[0081] Substrate/base layer 1: Ni--Fe--Cr (60)/antiferromagnetic
layer 2 [Pt--Cr sublayer 2A: Pt.sub.54 at %-Cr.sub.46 at %
(300-x)/X--Mn sublayer 2B: Pt.sub.50 at %-Mn.sub.50 at %
(x)]/pinned magnetic layer 3: Co.sub.90 at %-Fe.sub.10 at %
(50)/nonmagnetic material layer 4: Cu (40)/free magnetic layer 5:
Co.sub.90 at %-Fe.sub.10 at % (15)/Ni.sub.81.5 at %-Fe.sub.18.5 at
% (30)/protective layer 6: Ta (50)
[0082] For each exchange-coupled film 10 including the Pt--Cr
sublayer 2A and Pt--Mn sublayer having a thickness shown in Table
1, the Hex calculated from an R--H curve was as described below.
Hereinafter, Pt.sub.54 at %-Cr.sub.46 at % is appropriately
referred to as 54Pt--Cr, Pt.sub.51 at %-Cr.sub.49 at % is
appropriately referred to as 51Pt--Cr, and Pt.sub.50 at %-Mn.sub.50
at % is appropriately referred to as Pt--Mn.
TABLE-US-00001 TABLE 1 Thickness of 54Pt--Cr Thickness of Pt--Mn
sublayer sublayer Hex at room temperature D1 [.ANG.] (300 - x) D2
[.ANG.] (x) Hex [Oe] 300 0 238 298 2 364 296 4 519 294 6 634 292 8
790 290 10 917 288 12 1033 286 14 1149 284 16 1263 282 18 1348 280
20 1430 278 22 1462 276 24 1463 274 26 1466 272 28 1423 270 30 1372
266 34 1034 262 38 842 250 50 721 200 100 620 100 200 724 0 300
590
Example 4
[0083] Exchange-coupled films 10 having a film configuration below
were prepared by changing a Pt--Cr sublayer 2A of an
antiferromagnetic layer 2 from 54Pt--Cr (280-x) prepared in Example
3 to 51Pt--Cr (280-x). The exchange-coupled films 10 were annealed
at 400.degree. C. for 5 hours in a magnetic field of 1 kOe, whereby
the magnetization of each of a pinned magnetic layer 3 and the
antiferromagnetic layer 2 was pinned.
[0084] Substrate/base layer 1: Ni--Fe--Cr (60)/antiferromagnetic
layer 2 [Pt--Cr sublayer 2A: Pt.sub.51 at %-Cr.sub.49 at %
(300-x)/X--Mn sublayer 2B: Pt.sub.50 at %-Mn.sub.50 at %
(x)]/pinned magnetic layer 3: Co.sub.90 at %-Fe.sub.10 at %
(50)/nonmagnetic material layer 4: Cu (40)/free magnetic layer 5:
Co.sub.90 at %-Fe.sub.10 at % (15)/Ni.sub.81.5 at %-Fe.sub.18.5 at
% (30)/protective layer 6: Ta (50)
[0085] For each exchange-coupled film 10 including the Pt--Cr
sublayer 2A and Pt--Mn sublayer having a thickness shown in Table
2, the Hex calculated from an R--H curve was as described
below.
TABLE-US-00002 TABLE 2 Thickness of 51Pt--Cr Thickness of Pt--Mn
Hex at room temperature sublayer D1 [.ANG.] sublayer D2 [.ANG.] Hex
[Oe] 300 0 111 296 4 298 292 8 522 288 12 717 284 16 893 280 20
1039 276 24 1141 272 28 1113 250 50 610 200 100 523 100 200 663 0
300 590
Example 5
[0086] Exchange-coupled films 10 having the same film configuration
as that of Example 4 were prepared and the temperature of annealing
was changed from 400.degree. C. of Example 4 to 350.degree. C.
[0087] For each exchange-coupled film 10 including a 51Pt--Cr
sublayer and Pt--Mn sublayer having a thickness shown in Table 3,
the Hex calculated from an R--H curve was as described below.
TABLE-US-00003 TABLE 3 Thickness of 51Pt--Cr Thickness of Pt--Mn
Hex at room temperature sublayer D1 [.ANG.] sublayer D2 [.ANG.] Hex
[Oe] 300 0 210 296 4 407 292 8 709 288 12 840 284 16 951 280 20
1056 276 24 1064 272 28 1131 250 50 740 200 100 600 100 200 688 0
300 612
[0088] FIG. 8 is a graph showing the Hex of each of the
exchange-coupled films 10 prepared in Examples 3 to 5. In this
figure, the horizontal axis represents the thickness of a Pt--Mn
sublayer (Pt--Mn thickness, [.ANG.]) and the vertical axis
represents the Hex [Oe] of an exchange-coupled film. As is clear
from FIG. 8 and Tables 1 to 3, using either of 51Pt--Cr and
54Pt--Cr as a Pt--Cr sublayer allows the exchange-coupled films 10
to exhibit a higher Hex as compared to those including an
antiferromagnetic layer composed of a Pt--Mn sublayer only.
[0089] From the viewpoint of allowing an exchange-coupled film 10
to have a high Hex, 54Pt--Cr is preferably used as a Pt--Cr
sublayer. Even if the annealing temperature is 350.degree. C., an
exchange-coupled film 10 having substantially the same Hex as that
at 400.degree. C. is obtained. Therefore, from the viewpoint of
reducing the annealing temperature, 51Pt--Cr is preferably used as
a Pt--Cr sublayer.
Example 6
[0090] Exchange-coupled films 10 having a film configuration below
were prepared by changing an X--Mn sublayer 2B of an
antiferromagnetic layer 2 from Pt--Mn prepared in Example 3 to
Ir--Mn. The exchange-coupled films 10 were annealed at 400.degree.
C. for 5 hours in a magnetic field of 1 kOe, whereby the
magnetization of each of a pinned magnetic layer 3 and the
antiferromagnetic layer 2 was pinned.
[0091] Substrate/base layer 1: Ni--Fe--Cr (60)/antiferromagnetic
layer 2 [Pt--Cr sublayer 2A: Pt.sub.54 at %-Cr.sub.46 at %
(300-x)/X--Mn sublayer 2B: Ir.sub.50 at %-Mn.sub.50 at %
(x)]/pinned magnetic layer 3: Co.sub.90 at %-Fe.sub.10 at %
(50)/nonmagnetic material layer 4: Cu (40)/free magnetic layer 5:
Co.sub.90 at %-Fe.sub.10 at % (15)/Ni.sub.81.5 at %-Fe.sub.18.5 at
% (30)/protective layer 6: Ta (50)
[0092] For each exchange-coupled film 10 including a Pt--Cr
sublayer and Ir--Mn sublayer having a thickness shown in Table 4,
the Hex calculated from an R--H curve was as described below.
TABLE-US-00004 TABLE 4 Thickness of Pt--Cr Thickness of Ir--Mn Hex
at room temperature sublayer D1 [.ANG.] sublayer D2 [.ANG.] Hex
[Oe] 300 0 238 298 2 283 296 4 293 294 6 281 292 8 199 290 10 156
280 20 85 260 40 167 0 80 162
[0093] FIG. 9 is a graph showing the Hex of each of the
exchange-coupled films 10 prepared in Example 6. In this figure,
the horizontal axis represents the thickness of an Ir--Mn sublayer
(Ir--Mn thickness [.ANG.]) and the vertical axis represents the Hex
[Oe] of an exchange-coupled film. As is clear from FIG. 9 and Table
4, the effect of increasing the Hex of a Pt--Cr sublayer is
provided by an antiferromagnetic layer combined with Ir--Mn
similarly to a Pt--Mn sublayer.
Example 7
[0094] A magnetic sensing element 21 (refer to FIG. 2) including an
exchange-coupled film 20 having a film configuration below was
prepared. A parenthesized value is a thickness (.ANG.) The
exchange-coupled film 20 was annealed at 350.degree. C. for 5 hours
in no magnetic field and was thereby stabilized.
[0095] Substrate/base layer 1: Ni--Fe--Cr (42)/free magnetic layer
5: Ni.sub.81.5 at %-Fe.sub.18.5 at % (18)/:Co.sub.90 at %-Fe.sub.10
at % (14)/nonmagnetic material layer 4: Cu (30)/pinned magnetic
layer 3 [first magnetic sublayer 3A: Co.sub.90 at %-Fe.sub.10 at %
(24)/nonmagnetic intermediate sublayer 3B: Ru (3.6)]/second
magnetic sublayer 3C: Fe.sub.60 at %-Co.sub.40 at %
(17)/antiferromagnetic layer 2 [X--Mn sublayer: Pt.sub.50 at
%-Mn.sub.50 at % (20)/Pt.sub.51 at %-Cr.sub.49 at %
(280)]/protective layer 6: Ta (90)
Example 8
[0096] A magnetic sensing element 21 including an exchange-coupled
film 20 having a film configuration below was prepared by changing
an antiferromagnetic layer 2 from [X--Mn sublayer: Pt--Mn
(20)/51Pt--Cr (280)] prepared in Example 7 to [X--Mn sublayer:
Ir--Mn (4)/51Pt--Cr (296)].
[0097] Substrate/base layer 1: Ni--Fe--Cr (42)/free magnetic layer
5: Ni.sub.81.5 at %-Fe.sub.18.5 at % (18)/:Co.sub.90 at %-Fe.sub.10
at % (14)/nonmagnetic material layer 4: Cu (30)/pinned magnetic
layer 3 [first magnetic sublayer 3A: Co.sub.90 at %-Fe.sub.10 at %
(24)/nonmagnetic intermediate sublayer 3B: Ru (3.6)]/second
magnetic sublayer 3C: Fe.sub.60 at %-Co.sub.40 at %
(17)/antiferromagnetic layer 2 [X--Mn sublayer: Ir.sub.50 at
%-Mn.sub.50 at % (4)/Pt.sub.51 at %-Cr.sub.49 at %
(296)]/protective layer 6: Ta (90)
Comparative Example 2
[0098] A magnetic sensing element 21 including an exchange-coupled
film 20 having a film configuration below was prepared by changing
an antiferromagnetic layer 2 from [X--Mn sublayer: Pt--Mn
(20)/51Pt--Cr (280)] prepared in Example 7 to Pt--Mn (300).
[0099] Substrate/base layer 1: Ni--Fe--Cr (42)/free magnetic layer
5: Ni.sub.81.5 at %-Fe.sub.18.5 at % (18)/:Co.sub.90 at %-Fe.sub.10
at % (14)/nonmagnetic material layer 4: Cu (30)/pinned magnetic
layer 3 [first magnetic sublayer 3A: Co.sub.90 at %-Fe.sub.10 at %
(24)/nonmagnetic intermediate sublayer 3B: Ru (3.6)]/second
magnetic sublayer 3C: Fe.sub.60 at %-Co.sub.40 at %
(17)/antiferromagnetic layer 2: Pt.sub.50 at %-Mn.sub.50 at %
(300)/protective layer 6: Ta (90)
Application of External Magnetic Field
[0100] An external magnetic field H was applied to the magnetic
sensing element 21 prepared in each of Example 7, Example 8, and
Comparative Example 2 from a direction parallel to the pinned
magnetization direction (a P1 direction in FIG. 2) of the pinned
magnetic layer 3, whereby the rate of change in resistance
.DELTA.MR (.DELTA.R/R) was determined.
[0101] FIGS. 10A to 10C, FIGS. 11A to 11C, and FIGS. 12A to 12C
show R--H curves of the magnetic sensing element 21 prepared in
Example 7, R--H curves of the magnetic sensing element 21 prepared
in Example 8, and R--H curves of the magnetic sensing element 21
prepared in Comparative Example 2, respectively. In each of these
figures, the horizontal axis represents the intensity [Oe] of the
magnetic field H, the vertical axis represents .DELTA.MR (%), a
curve marked "Inc." represents .DELTA.MR in the case of increasing
the magnetic field H, and a curve marked "Dec." represents
.DELTA.MR in the case of reducing the magnetic field H.
[0102] FIGS. 10A to 10C and FIGS. 11A to 11C show less hysteresis
as compared to FIGS. 12A to 12C and show an improvement in a
.DELTA.MR reduction process down to +5 kOe. This result shows that
an antiferromagnetic layer which is composed of a Pt--Cr sublayer
and a Pt--Mn sublayer and in which the Pt--Mn sublayer is in
contact with a pinned magnetic layer enhances the stabilization of
an exchange-coupled film even when the pinned magnetic layer is a
self-pinned layer including a first magnetic sublayer, intermediate
sublayer, and second magnetic sublayer which are stacked.
Reference Example 1
[0103] Magnetic sensing elements having a film configuration below
were prepared. A parenthesized value is a thickness (.ANG.). Each
exchange-coupled film 10 was annealed at 400.degree. C. for 5 hours
in a magnetic field of 1 kOe, whereby the magnetization of each of
a pinned magnetic layer 3 and an antiferromagnetic layer 2 were
pinned.
[0104] Substrate/base layer 1: Ni--Fe--Cr (60)/antiferromagnetic
layer 2: Pt.sub.XCr.sub.100 at %-X (300)/pinned magnetic layer 3:
Co.sub.90 at %-Fe.sub.10 at % (50)/nonmagnetic material layer 4: Cu
(40)/free magnetic layer 5: [Co.sub.90 at %-Fe.sub.10 at %
(15)/81.5Ni--Fe (30)]/protective layer 6: Ta (50)
[0105] By co-sputtering Pt and Cr, Pt.sub.XCr.sub.100 at %-X (300)
films having different Pt-to-Cr ratios were prepared.
Reference Example 2
[0106] Pt.sub.XCr.sub.100 at %-X (300) films having different
Pt-to-Cr ratios were prepared in substantially the same manner as
that used in Reference Example 1 except that Pt and Cr were
alternately stacked instead of co-sputtering Pt and Cr.
Reference Example 3
[0107] Pt.sub.XCr.sub.100 at %-X (300) films having different
Pt-to-Cr ratios were prepared in substantially the same manner as
that used in Example 1 except that a base layer 1 was changed from
Ni--Fe--Cr (60) prepared in Example 1 to Ta (50).
Sputtering and Alternate Stacking
[0108] FIG. 13 is a graph showing the relationship between the
percentage of Pt contained in Pt--Cr prepared in each of Reference
Example 1 (co-sputtering) and Reference Example 2 (alternate
stacking) and the Hex. As is clear from this figure, Reference
Example 1, in which Pt.sub.XCr.sub.100 at %-X films were formed by
co-sputtering, provides a higher Hex as compared to Reference
Example 2, in which Pt.sub.XCr.sub.100 at %-X films were formed by
alternate stacking, within the Pt percentage range of 51 at % to 57
at %.
Base Layer
[0109] FIG. 14 is a graph showing the relationship between the
percentage of Pt contained in Pt--Cr prepared in each of Reference
Example 1 and Reference Example 3 and the Hex. As is clear from
this figure, exchange-coupled films Reference Example 1 (Ni--Fe--Cr
base) exhibits a significantly higher Hex as compared to Reference
Example 3 (Ta base) within the Pt percentage range of 51 at % to 57
at %.
Example 9
[0110] In order to investigate the relationship between the
temperature and the Hex, an exchange-coupled film 40 having a
structure shown in FIG. 15 was prepared.
[0111] Substrate/base layer 1: Ni--Fe--Cr (42)/antiferromagnetic
layer 2/pinned magnetic layer 3: 90Co--Fe (100)/protective layer 6:
Ta (90)
[0112] The exchange-coupled film 40 was formed by setting an
antiferromagnetic layer 2 to 51Pt--Cr (280)/Pt--Mn (20) and was
annealed at 350.degree. C. for 5 hours in a magnetic field of 1 kOe
such that the magnetization of each of a pinned magnetic layer 3
and the antiferromagnetic layer 2 was pinned.
Comparative Example 3
[0113] An exchange-coupled film 40 was formed by setting an
antiferromagnetic layer 2 to 51Pt--Cr (300) and was annealed at
350.degree. C. for 5 hours in a magnetic field of 1 kOe such that
the magnetization of each of a pinned magnetic layer 3 and the
antiferromagnetic layer 2 was pinned.
[0114] Table 5 shows results obtained by measuring the
exchange-coupled film 40 prepared in each of Example 9 and
Comparative Example 3 for a change in Hex due to a change in
temperature. In Tables 5 to 7, Tb represents the temperature at
which the Hex vanishes and Hex (200.degree. C. or 300.degree.
C.)/Hex (room temperature) represents a normalized value obtained
by dividing the Hex at 200.degree. C. or 300.degree. C. by the Hex
at room temperature.
TABLE-US-00005 TABLE 5 Thickness of Thickness 51Pt--Cr of Pt--Mn
Hex (200.degree. C.)/ Hex (300.degree. C.)/ sublayer sublayer Tb
Hex (room Hex (room D1 [.ANG.] D2 [.ANG.] (.degree. C.)
temperature) temperature) 300 0 460 0.96 0.66 280 20 >500 0.88
0.75
Example 10
[0115] An exchange-coupled film 40 was formed by setting an
antiferromagnetic layer 2 to 51Pt--Cr (280)/Pt--Mn (20) and was
annealed at 400.degree. C. for 5 hours in a magnetic field of 1 kOe
such that the magnetization of each of a pinned magnetic layer 3
and the antiferromagnetic layer 2 was pinned.
Comparative Example 4
[0116] An exchange-coupled film 40 was formed by setting an
antiferromagnetic layer 2 to Pt--Mn (300) and was annealed at
400.degree. C. for 5 hours in a magnetic field of 1 kOe such that
the magnetization of each of a pinned magnetic layer 3 and the
antiferromagnetic layer 2 was pinned.
[0117] Table 6 shows measurement result of Example 10 and
Comparative Example 4.
TABLE-US-00006 TABLE 6 Thickness Thickness of of Pt--Mn Hex
(200.degree. C.)/ Hex (300.degree. C.)/ 51Pt--Cr sublayer sublayer
Tb Hex (room Hex (room D1 [.ANG.] D2 [.ANG.] (.degree. C.)
temperature) temperature) 280 20 >500 0.86 0.76 0 300 400 0.82
0.35
Example 11
[0118] An exchange-coupled film 40 was formed by setting an
antiferromagnetic layer 2 to 54Pt--Cr (290)/Pt--Mn (10) and was
annealed at 400.degree. C. for 5 hours in a magnetic field of 1 kOe
such that the magnetization of each of a pinned magnetic layer 3
and the antiferromagnetic layer 2 was pinned.
Example 12
[0119] An exchange-coupled film 40 was formed by setting an
antiferromagnetic layer 2 to 54Pt--Cr (280)/Pt--Mn (20) and was
annealed at 400.degree. C. for 5 hours in a magnetic field of 1 kOe
such that the magnetization of each of a pinned magnetic layer 3
and the antiferromagnetic layer 2 was pinned.
[0120] Table 7 shows measurement result of Examples 11 and 12 and
Comparative Example 4.
TABLE-US-00007 TABLE 7 Thickness Thickness of of Pt--Mn Hex
(200.degree. C.)/ Hex (300.degree. C.)/ 54Pt--Cr sublayer sublayer
Tb Hex (room Hex (room D1 [.ANG.] D2 [.ANG.] (.degree. C.)
temperature) temperature) 290 10 500 0.98 0.86 280 20 >500 0.91
0.80 0 300 400 0.82 0.35
[0121] FIG. 16 is a graph showing the relationship between the
temperature of the exchange-coupled film 40 prepared in each of
Examples 9 to 12 and Comparative Examples 3 and 4 and the Hex. This
graph shows results obtained by measuring the quantity
corresponding to the Hex in the R--H curve of each of FIGS. 5 to 7
using a VSM (vibrating sample magnetometer).
[0122] As shown in FIG. 16 and Tables 5 to 7, an exchange-coupled
film 40 including an antiferromagnetic layer 2 including a Pt--Mn
sublayer and a Pt--Cr sublayer inserted therein exhibited higher Tb
as compared to an exchange-coupled film including an
antiferromagnetic layer 2 made of Pt--Mn only and also exhibited
high stability under high-temperature conditions for maintaining
high Hex.
* * * * *