U.S. patent application number 17/094171 was filed with the patent office on 2021-05-20 for magnetic sensor.
The applicant listed for this patent is TDK Corporation. Invention is credited to Hiraku Hirabayashi, Yoshihiro Kudo, Yuta Saito.
Application Number | 20210149000 17/094171 |
Document ID | / |
Family ID | 1000005252741 |
Filed Date | 2021-05-20 |
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United States Patent
Application |
20210149000 |
Kind Code |
A1 |
Saito; Yuta ; et
al. |
May 20, 2021 |
MAGNETIC SENSOR
Abstract
A magnetic sensor includes a magnetic sensor tip that includes a
magnetoresistive effect element and a sealed part. The
magnetoresistive effect element includes a free layer and a pinned
layer. The sealed part has a first surface and a second surface,
which is opposite the first surface. The shape of the sealed part
in the plan view from the first surface side is substantially
quadrilateral. The substantially quadrilateral shape has a first
side and a second side, which are substantially parallel to each
other. In the plan view, from the first surface side of the sealed
part, the magnetization direction of the pinned layer, in a state
in which the external magnetic field is not applied on the
magnetoresistive effect element, is inclined with respect to an
approximately straight line found through the least squares method
using a plurality of points arbitrarily set on the first side.
Inventors: |
Saito; Yuta; (Tokyo, JP)
; Hirabayashi; Hiraku; (Tokyo, JP) ; Kudo;
Yoshihiro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TDK Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
1000005252741 |
Appl. No.: |
17/094171 |
Filed: |
November 10, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 33/098 20130101;
G01R 33/093 20130101 |
International
Class: |
G01R 33/09 20060101
G01R033/09 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2019 |
JP |
2019-208486 |
Claims
1. A magnetic sensor comprising: a magnetic sensor tip that
includes a magnetoresistive effect element; and a sealed part that
seals the magnetic sensor tip; wherein the magnetoresistive effect
element includes a free layer, the magnetization direction of which
can change in accordance with an external magnetic field, and a
pinned layer, the magnetization direction of which is fixed; the
sealed part has a first surface and a second surface, which is
opposite the first surface; the shape of the sealed part in the
plan view from the first surface side is substantially
quadrilateral; the substantially quadrilateral shape has a first
side and a second side, which are substantially parallel to each
other, and a third side and a fourth side, which are substantially
parallel to each other and that intersect the first side and the
second side; and in the plan view from the first surface side of
the sealed part, the magnetization direction of the pinned layer,
in a state in which the external magnetic field is not applied on
the magnetoresistive effect element, is inclined with respect to an
approximately straight line found through the least squares method
using a plurality of points arbitrarily set on the first side.
2. The magnetic sensor according to claim 1, wherein the
magnetization direction of the pinned layer, in a state in which
the external magnetic field is not applied on the magnetoresistive
effect element, is inclined at an angle of 10.about.80.degree. with
respect to the approximately straight line.
3. The magnetic sensor according to claim 1, wherein: the shape in
the plan view of the magnetic sensor tip is substantially a
quadrilateral having a first side and a second side substantially
parallel to each other, and a third side and a fourth side
substantially parallel to each other and intersecting the first
side and the second side; the first side of the magnetic sensor tip
and the approximately straight line are substantially parallel; and
when the magnetic sensor tip is viewed from the first surface side
of the sealed part, the magnetization direction of the pinned layer
in a state in which the external magnetic field is not applied on
the magnetoresistive effect element is inclined with respect to the
first side of the magnetic sensor tip.
4. The magnetic sensor according to claim 1, wherein: the shape in
the plan view of the magnetic sensor tip is substantially a
quadrilateral having a first side and a second side, which are
substantially parallel to each other, and a third side and a fourth
side, which are substantially parallel to each other and which
intersect the first side and the second side; and when the magnetic
sensor tip is viewed from the first surface side of the sealed
part, the magnetization direction of the pinned layer, in a state
in which the external magnetic field is not applied on the
magnetoresistive effect element, is substantially parallel to or
substantially orthogonal to the first side of the magnetic sensor
tip, and the first side of the magnetic sensor tip is inclined with
respect to the approximately straight line.
5. The magnetic sensor according to claim 1, wherein: the magnetic
sensor tip includes a plurality of the magnetoresistive effect
elements; and the magnetization directions of the free layers of
the magnetoresistive effect elements in a state in which the
external magnetic field is not applied on the plurality of
magnetoresistive effect elements correspond to each other.
6. The magnetic sensor according to claim 1, wherein the
magnetoresistive effect element is a GMR element or a TMR
element.
7. The magnetic sensor according to claim 1, wherein the sealed
part includes a resin.
Description
[0001] The present application is based on Japanese Patent
Application No. 2019-208486 filed on Nov. 19, 2019, the disclosure
of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a magnetic sensor.
BACKGROUND
[0003] Magnetoresistive effect elements (MR elements) such as giant
magnetoresistive effect elements (GMR elements), tunnel
magnetoresistive effect elements (TMR elements), anisotropic
magnetoresistive effect elements (MR elements) and the like have
been applied in the field of magnetic sensors. For example, GMR
elements or TMR elements include a pinned layer, in which the
magnetization direction is fixed, and a free layer, in which the
magnetization direction changes in accordance with an external
magnetic field. When the strength of the external magnetic field
applied on the magnetoresistive effect element changes, the
magnetization direction of the free layer changes and the angle
formed by the magnetization direction of the pinned layer and the
magnetization direction of the free layer changes. Through the
change in this angle, the resistance value of the magnetoresistive
effect element changes, and through the change in this resistance
value, it is possible to detect changes in the strength of the
external magnetic field.
[0004] A magnetic sensor that uses this kind of magnetoresistive
effect element, for example, has at least a magnetic sensor tip
comprising a magnetoresistive effect element and a sealed part,
which is sealed in order to protect this magnetic sensor tip, and
is used, for example, as an electric current sensor, an angle
sensor or the like.
PATENT LITERATURE
[0005] PATENT LITERATURE 1 JP Laid-Open Patent Application No.
2009-162499
Problem to be Solved by the Invention
[0006] In a magnetic sensor having a configuration in which the
magnetic sensor tip is sealed by the sealed part, stress from
outside the magnetic sensor is at times applied on the magnetic
sensor tip during and after manufacturing of the magnetic sensor.
When an external magnetic field is not applied on the
magnetoresistive effect element, the magnetization of the free
layer is oriented in a fixed direction by a bias magnet, but when
the stress is received, the magnetization direction of the free
layer may change due to an inverse magnetostrictive effect. When
the magnetization direction of the free layer on which an external
magnetic field is not applied changes from the prescribed
direction, there is a concern that there could be an effect on the
change in the resistance value of the magnetoresistive effect
element when an external magnetic field is applied, that is, on the
output of the magnetic sensor when an external magnetic field is
applied. For example, in an electric current sensor that uses a
magnetic sensor having a magnetoresistive effect element, the
electric current value detected in a state in which stress is
applied on the magnetic sensor tip includes errors, creating the
problem that this kind of magnetic sensor cannot be used in
applications in which the electric current value or the like that
is the target of detection needs to be detected stably and with
high precision.
[0007] In addition, a TMR-type magnetoresistive effect element has
a high MR ratio compared to a GMR-type or AMR-type magnetoresistive
effect element and has markedly superior output properties but is
also sensitive to external stress applied on the magnetic sensor
tip, the output of the magnetic sensor could be greatly
affected.
[0008] External stress applied on the magnetic sensor tip is
difficult to predict, and even if such could be predicted,
controlling such external stress is difficult. Accordingly, in
order to secure the detection precision of the magnetic sensor, it
is desirable for the magnetic sensor to have a configuration in
which output is unlikely to be greatly caused to fluctuate by
external stress.
[0009] In consideration of the foregoing, it is an object of the
present invention to provide a magnetic sensor in which it is
possible to suppress fluctuations in output caused by stress
applied from the outside.
Means for Solving the Problem
[0010] To achieve such an object, the present invention provides a
magnetic sensor comprising a magnetic sensor tip that includes a
magnetoresistive effect element and a sealed part that integrally
seals the magnetic sensor tip. The magnetoresistive effect element
includes a free layer, the magnetization direction of which can
change in accordance with an external magnetic field, and a pinned
layer, the magnetization direction of which is fixed. The sealed
part has a first surface and a second surface, which is opposite
the first surface. The shape of the sealed part in the plan view
from the first surface side is substantially quadrilateral. The
substantially quadrilateral shape has a first side and a second
side, which are substantially parallel to each other, and a third
side and a fourth side, which are substantially parallel to each
other and that intersect the first side and the second side. In the
plan view from the first surface side of the sealed part, the
magnetization direction of the pinned layer, in a state in which
the external magnetic field is not applied on the magnetoresistive
effect element, is inclined with respect to an approximately
straight line found through the least squares method using a
plurality of points arbitrarily set on the first side.
[0011] The magnetization direction of the pinned layer, in a state
in which the external magnetic field is not applied on the
magnetoresistive effect element, may be inclined at an angle of
10.about.80.degree. with respect to the approximately straight
line.
[0012] The shape in the plan view of the magnetic sensor tip may be
substantially a quadrilateral having a first side and a second
side, which are substantially parallel to each other, and a third
side and a fourth side, which are substantially parallel to each
other and which intersect the first side and the second side, the
first side of the magnetic sensor tip and the approximately
straight line are substantially parallel, and when the magnetic
sensor tip is viewed from the first surface side of the sealed
part, the magnetization direction of the pinned layer in a state in
which the external magnetic field is not applied on the
magnetoresistive effect element may be inclined with respect to the
first side of the magnetic sensor tip.
[0013] The shape in the plan view of the magnetic sensor tip may be
substantially a quadrilateral having a first side and a second
side, which are substantially parallel to each other, and a third
side and a fourth side, which are substantially parallel to each
other and which intersect the first side and the second side, and
when the magnetic sensor tip is viewed from the first surface side
of the sealed part, the magnetization direction of the pinned
layer, in a state in which the external magnetic field is not
applied on the magnetoresistive effect element, may be
substantially parallel to or substantially orthogonal to the first
side of the magnetic sensor tip, and the first side of the magnetic
sensor tip may be inclined with respect to the approximately
straight line.
[0014] The magnetic sensor tip may include a plurality of the
magnetoresistive effect elements and the magnetization directions
of the free layers of the magnetoresistive effect elements in a
state in which the external magnetic field is not applied on the
plurality of magnetoresistive effect elements may correspond to
each other, the magnetoresistive effect element may be a GMR
element or a TMR element, and the sealed part may include a
resin.
EFFICACY OF THE INVENTION
[0015] With the present invention, it is possible to provide a
magnetic sensor in which it is possible to suppress fluctuations in
output caused by stress applied from the outside.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic cross-sectional view showing a
schematic configuration from a side perspective of a magnetic
sensor according to an embodiment of the present invention.
[0017] FIG. 2 is a plan view showing the schematic configuration of
the internal structure in a plan view from a first surface side of
the sealed part of the magnetic sensor shown in FIG. 1.
[0018] FIG. 3A is a circuit diagram showing the schematic
configuration of the magnetic sensor according to the embodiment of
the present invention.
[0019] FIG. 3B is a graph showing measurement results for output of
the magnetic sensor shown in FIG. 3A.
[0020] FIG. 3C is a circuit diagram showing the schematic
configuration in a state in which stress at a 45.degree. direction
is applied on the magnetic sensor shown in FIG. 3A.
[0021] FIG. 3D is a graph showing measurement results for output of
the magnetic sensor shown in FIG. 3C.
[0022] FIG. 4A is a perspective view showing the schematic
configuration of the magnetoresistive effect element of the
magnetic sensor according to the embodiment of the present
invention.
[0023] FIG. 4B is a plan view when the magnetoresistive effect
element shown in FIG. 4A is viewed from the free layer side.
[0024] FIG. 5A is a schematic diagram conceptually showing the
magnetization of the free layer in a state in which an external
magnetic field is not applied.
[0025] FIG. 5B is a schematic diagram conceptually showing the
magnetization of the pinned layer in a state in which an external
magnetic field is not applied.
[0026] FIG. 6 is a plan view showing the positional relationship
between the magnetization direction of the pinned layer and the
sealed part and magnetic sensor tip of the magnetic sensor
according to the embodiment of the present invention.
[0027] FIG. 7 is a plan view showing the positional relationship
between the magnetization direction of the pinned layer and the
sealed part and magnetic sensor tip of the magnetic sensor
according to another embodiment of the present invention.
[0028] FIG. 8A is a graph showing the relationship between voltage
offset and the applied angle of external stress at an output
voltage V1 when the pinned layer of the magnetic sensor is inclined
at 0.degree., 10.degree., 20.degree., 30.degree. and 45.degree.,
respectively.
[0029] FIG. 8B is a graph showing the relationship between voltage
offset and the applied angle of external stress at an output
voltage V2 when the pinned layer of the magnetic sensor is inclined
at 0.degree., 10.degree., 20.degree., 30.degree. and 45.degree.,
respectively.
[0030] FIG. 8C is a graph showing the relationship between voltage
offset and the applied angle of external stress at an output
voltage (V1-V2) when the pinned layer of the magnetic sensor is
inclined at 0.degree., 10.degree., 20.degree., 30.degree. and
45.degree. respectively.
[0031] FIG. 9A is a graph showing the relationship between voltage
offset and the applied angle of external stress at an output
voltage V1 when the pinned layer of the magnetic sensor is inclined
at 90.degree., 80.degree., 70.degree., 60.degree. and 45.degree.,
respectively.
[0032] FIG. 9B is a graph showing the relationship between voltage
offset and the applied angle of external stress at an output
voltage V2 when the pinned layer of the magnetic sensor is inclined
at 90.degree., 80.degree., 70.degree., 60.degree. and 45.degree.,
respectively.
[0033] FIG. 9C is a graph showing the relationship between voltage
offset and the applied angle of external stress at an output
voltage (V1-V2) when the pinned layer of the magnetic sensor is
inclined at 90.degree., 80.degree., 70.degree., 60.degree. and
45.degree., respectively.
[0034] FIG. 10A is an end view showing a schematic configuration of
an electric current sensor equipped with the magnetic sensor of the
present invention.
[0035] FIG. 10B is a cross-sectional view along line A-A of the
electric current sensor shown in FIG. 10A.
[0036] FIG. 11 is a perspective view showing the schematic
configuration of a magnetoresistive effect element of a magnetic
sensor according to another embodiment of the present
invention.
[0037] FIG. 12A is a side view of the magnetic sensor fixed to a
substrate.
[0038] FIG. 12B is a side view when a plate is pressed against the
back side of the substrate.
[0039] FIG. 12C is a top view when a plate is pressed against the
substrate at a 45.degree. angle with respect to an approximately
straight line.
[0040] FIG. 13A is a graph showing the relationship between the
voltage offset and the displacement in Embodiment 1 when an
external stress is applied at a 0.degree. angle.
[0041] FIG. 13B is a graph showing the relationship between the
voltage offset and the displacement in Embodiment 1 when an
external stress is applied at a 45.degree. angle.
[0042] FIG. 13C is a graph showing the relationship between the
voltage offset and the displacement in Embodiment 1 when an
external stress is applied at a 90.degree. angle.
[0043] FIG. 14A is a graph showing the relationship between the
voltage offset and the displacement in Embodiment 2 when an
external stress is applied at a 0.degree. angle.
[0044] FIG. 14B is a graph showing the relationship between the
voltage offset and the displacement in Embodiment 2 when an
external stress is applied at a 45.degree. angle.
[0045] FIG. 14C is a graph showing the relationship between the
voltage offset and the displacement in Embodiment 2 when an
external stress is applied at a 90.degree. angle.
[0046] FIG. 15A is a plan view from a first surface side of the
magnetic sensor of Comparison Example 1.
[0047] FIG. 15B is a plan view from a first surface side of the
magnetic sensor of Comparison Example 2.
[0048] FIG. 16A is a graph showing the relationship between the
voltage offset and displacement in Comparison Example 1 when an
external stress is applied at a 0.degree. angle.
[0049] FIG. 16B is a graph showing the relationship between the
voltage offset and displacement in Comparison Example 1 when an
external stress is applied at a 45.degree. angle.
[0050] FIG. 16C is a graph showing the relationship between the
voltage offset and displacement in Comparison Example 1 when an
external stress is applied at a 90.degree. angle.
[0051] FIG. 17A is a graph showing the relationship between the
voltage offset and displacement in Comparison Example 2 when an
external stress is applied at a 0.degree. angle.
[0052] FIG. 17B is a graph showing the relationship between the
voltage offset and displacement in Comparison Example 2 when an
external stress is applied at a 45.degree. angle.
[0053] FIG. 17C is a graph showing the relationship between the
voltage offset and displacement in Comparison Example 2 when an
external stress is applied at a 90.degree. angle.
BEST MODE FOR IMPLEMENTING THE INVENTION
[0054] Below, an embodiment of the magnetic sensor of the present
invention is described with reference to the drawings.
[0055] In the description of the magnetic sensor according to this
embodiment, as necessary the "X direction, Y direction and Z
direction" are stipulated in a number of the drawings. Here, the X
direction matches the magnetization direction of the pinned layer
of the magnetoresistive effect element. The Y direction is a
direction orthogonal to the X direction and matches the
magnetization direction of the free layer in a state in which an
external magnetic field is not applied. The Z direction is a
direction orthogonal to the X direction and the Y direction and
matches the layering direction of the multilayer film of the
magnetoresistive effect element.
[0056] The orientation of arrows indicating the X, Y and Z
directions in each of the drawings indicates the +X direction, +Y
direction and +Z direction, and the orientation on the opposite
side from the orientation of the arrows indicates the -X direction,
-Y direction and -Z direction.
[0057] FIG. 1 is a schematic cross-sectional view showing a
schematic configuration from a side perspective of a magnetic
sensor according to this embodiment, and FIG. 2 is a plan view
showing the schematic configuration of the internal structure from
a first surface side of the sealed part of the magnetic sensor
shown in FIG. 1.
[0058] As shown in FIG. 1 and FIG. 2, a magnetic sensor 1 includes
a magnetic sensor tip 2 and a sealed part 3, which is sealed
integrally with the magnetic sensor tip 2. The sealed part 3 has a
first surface 3a and a second surface 3b, which is opposite the
first surface 3a, and the shape of the sealed part 3 in a plan view
from the first surface 3a side is a substantially quadrilateral
shape with a first side 31 and second side 32, which are
substantially parallel to each other, and a third side 33 and a
fourth side 34, which are substantially parallel to each other and
intersect the first side 31 and the second side 32. Preferably, the
sealed part 3 has the first surface 3a and the second surface 3b,
which is opposite the first surface 3a. The shape of the sealed
part 3 in a plan view from the first surface 3a side is a
substantially square shape having the first side 31 and the second
side 32, which are substantially parallel to each other. The third
side 33 and the fourth side 34 are substantially parallel to each
other and substantially orthogonal to the first side 31 and the
second side 32.
[0059] The magnetic sensor tip 2 has a substantially quadrilateral
shape with a first side 21 and a second side 22, which are
substantially parallel to each other in the plan view, and a third
side 23 and a fourth side 24, which are substantially parallel to
each other and which intersect the first side 21 and the second
side 22. Preferably, the magnetic sensor tip 2 is a substantially
square shape with the first side 21 and the second side 22
substantially parallel to each other in the plan view and the third
side 23 and the fourth side 24 substantially parallel to each other
and substantially orthogonal to the first side 21 and the second
side 22. In addition, the magnetic sensor tip 2 comprises a
magnetoresistive effect element. As the magnetoresistive effect
element, it is possible, for example, to use a giant
magnetoresistive effect (GMR) type magnetoresistive effect element
or a tunnel magnetoresistive effect (TMR) type magnetoresistive
effect element.
[0060] In this embodiment, substantially parallel and substantially
orthogonal and substantially quadrilateral shape and substantially
square shape are concepts that include manufacturing errors and the
like at the time of manufacturing the magnetic sensor tip 2 and the
sealed part 3.
[0061] For substantially parallel, an extension line extending
along the first side 31 of the sealed part 3 and an extension line
extending along the second side 32 may intersect so that the angle
formed by the two extension lines is 3.degree. or less. For
substantially orthogonal, the angle formed by the first side 31 and
the third side 33 or the angle formed by an extension line
extending along the first side 31 and an extension line extending
along the third side 33 may be within the range of
89.about.91.degree.. In addition, for the substantially
quadrilateral shape and the substantially square shape, in the plan
view from the first surface 3a side, the first surface 3a of the
sealed part 3 may be a quadrilateral with rounded corners, a square
with rounded corners, a rectangle with rounded corners, or a
quadrilateral in which C-chamfering has been implemented on the
corners, a square in which C-chamfering has been implemented on the
corners, a rectangle in which C-chamfering has been implemented on
the corners, or the like. Furthermore, for substantially parallel,
an extension line extending along the first side 21 of the magnetic
sensor tip 2 and an extension line extending along the second side
32 may intersect so that the angle formed by the two extension
lines is 3.degree. or less. For substantially orthogonal, the angle
formed by the first side 21 and the third side 23 or the angle
formed by an extension line extending along the first side 21 and
an extension line extending along the third side 23, may be within
the range of 89.about.91.degree.. Furthermore, for a substantially
quadrilateral shape and a substantially square shape, in the plan
view, the magnetic sensor tip 2 may be a quadrilateral with rounded
corners, a square with rounded corners, a rectangle with rounded
corners, or a quadrilateral in which C-chamfering has been
implemented on the corners, a square in which C-chamfering has been
implemented on the corners, a rectangle in which C-chamfering has
been implemented on the corners, or the like.
[0062] The sealed part 3 possessed by the magnetic sensor 1 should
be one that is sealed integrally with and protects the magnetic
sensor tip 2 and, for example, may be composed of resin. When
stress from the outside is applied on the magnetic sensor 1, the
sealed part 3 can mitigate the effects of stress applied on the
magnetic sensor tip 2 by exhibiting a cushioning action against
this stress. The elastic modulus of the resin composing this sealed
part 3 should be for example around 0.1.about.50 GPa. Examples of
the resin that can form the sealed part 3 include epoxy resin,
styrene resin, ABS resin and the like. The dimensions of the sealed
part 3 are not particularly limited as long as the magnetic sensor
tip 2 can be integrally sealed and can be appropriately set in
accordance with the application or the like.
[0063] The magnetic sensor 1 according to this embodiment may also
comprise a die pad 4 having a mounting surface for mounting the
magnetic sensor tip 2, a plurality of lead wires 5 placed
surrounding the die pad 4, and a wiring unit 6 that electrically
connects the lead wires 5 and the terminals of the magnetic sensor
tip 2. The die pad 4 should be composed of an electrically
conductive material such as copper or the like. The magnetic sensor
tip 2 should be fixed to the mounting surface of the die pad 4 by
an adhesive (undepicted) such as conductive paste, insulating
paste, die attach film (DAF) or the like. The wiring unit 6 can be
composed of bonding wire or the like made of gold wires or the
like.
[0064] FIG. 3A is a circuit diagram showing the schematic
configuration of the magnetic sensor according to this embodiment.
The magnetic sensor 1 includes a first magnetoresistive effect
element 11, a second magnetoresistive effect element 12, a third
magnetoresistive effect element 13 and a fourth magnetoresistive
effect element 14, and the first through fourth magnetoresistive
effect elements 11.about.14 are connected to each other with a
bridge circuit (Wheatstone bridge). The first through fourth
magnetoresistive effect elements 11.about.14 are divided into two
groups, namely a group consisting of the first magnetoresistive
effect element 11 and the second magnetoresistive effect element 12
and a group consisting of the third magnetoresistive effect element
13 and the fourth magnetoresistive effect element 14, and the
magnetoresistive effect elements within each of these pairs are
connected in series. The first magnetoresistive effect element 11
and the fourth magnetoresistive effect element 14 are connected to
a power source voltage Vcc, and the second magnetoresistive effect
element 12 and the third magnetoresistive effect element 13 are
connected to ground (GND). The output voltage between the first
magnetoresistive effect element 11 and the second magnetoresistive
effect element 12 is taken out as a midpoint voltage V1, and the
output voltage between the third magnetoresistive effect element 13
and the fourth magnetoresistive effect element 14 is taken out as a
midpoint voltage V2. Accordingly, when the electrical resistances
of the first through fourth magnetoresistive effect elements
11.about.14 are called R1.about.R4, respectively, the midpoint
voltages V1 and V2 can be found from the following equations (1)
and (2), respectively.
Formula 1 ] V 1 = R 2 R 1 + R 2 V cc ( 1 ) Formula 2 ] V 2 = R 3 R
3 + R 4 V cc ( 2 ) ##EQU00001##
[0065] In this embodiment, the description takes as an example a
configuration in which each of the first through fourth
magnetoresistive effect elements 11.about.14 comprises a single
magnetoresistive effect element, but each of the first through
fourth magnetoresistive effect elements 11.about.14 may comprise a
plurality of magnetoresistive effect elements, or each of the first
through fourth magnetoresistive effect elements 11.about.14 may
comprise a plurality of magnetoresistive effect elements connected
in series.
[0066] Because the first through fourth magnetoresistive effect
elements 11.about.14 have the same structure, the description will
take the first magnetoresistive effect element 11 as an example.
FIG. 4A is a perspective view showing the schematic configuration
of the magnetoresistive effect element (the first magnetoresistive
effect element 11) of the magnetic sensor according to this
embodiment. The first magnetoresistive effect element 11 includes a
multilayer film 40, which has a substantially rectangular in the
plan view, and a pair of bias magnets 47, which are positioned at
both ends of the multilayer film 40 in the lengthwise direction so
that the multilayer film 40 is located in between the bias magnets
47. The multilayer film 40 has a general spin-valve-type film
composition. The multilayer film 40 includes an antiferromagnetic
layer 41, a pinned layer 42, a spacer layer 45 and a free layer 46,
and these layers are layered in this order. The multilayer film 40
is located between a pair of electrode layers (undepicted) in this
layering direction and is configured so that a sense electric
current flows in the layering direction from the electrode layer to
the multilayer film 40. In this embodiment, the shape of the
multilayer film 40 in the plan view is a substantially square shape
but may be a substantially rectangular shape. Here, the
substantially square shape or substantially rectangular shape
includes, besides a square shape and a rectangular shape, a square
shape having rounded corners, a rectangular shape having rounded
corners, and the like. In addition, in this embodiment, the first
through fourth magnetoresistive effect elements 11.about.14 have a
pair of bias magnets 47 with the multilayer film 40 located in
between the bias magnets 47, but this is intended to be
illustrative and not limiting and, for example, in the case of a
rectangular shape or oval shape including an ellipse in which the
multilayer film 40 uses magnetic shape anisotropy, the bias magnets
47 need not be present.
[0067] The free layer 46 is a magnetic layer, the magnetization
direction of which changes in accordance with the external magnetic
field, and is composed of, for example, NiFe, CoFe, CoFeB, CoFeNi,
Co.sub.2MnSi, Co.sub.2MnGe, FeO.sub.X (Fe oxides), or the like. The
pinned layer 42 is a ferromagnetic layer, the magnetization
direction of which is fixed with respect to the external magnetic
field through exchange coupling with the antiferromagnetic layer 41
and is composed of the same magnetic material as the free layer 46.
The antiferromagnetic layer 41 is composed, for example, of an
antiferromagnetic material including Mn and at least one type of
element selected from among the group of Pt, Ru, Rh, Pd, Ni, Cu,
Ir, Cr and Fe. The Mn content in the antiferromagnetic material
should be around 35.about.95 atom %, for example. The spacer layer
45 is positioned between the free layer 46 and the pinned layer 42
and is a nonmagnetic layer that exhibits the magnetoresistive
effect. The spacer layer 45 is a nonmagnetic conductive layer
composed of a nonmagnetic metal, such as Cu or the like, or is a
tunnel barrier layer composed of a nonmagnetic insulator such as
Al.sub.2O.sub.3. When the spacer layer 45 is a nonmagnetic
conductive layer, the first magnetoresistive effect element 11
functions as a giant magnetoresistive effect (GMR) element, and
when the spacer layer 45 is a tunnel barrier layer, the first
magnetoresistive effect element 11 functions as a tunnel
magnetoresistive effect (TMR) element. To make the magnetoresistive
effect large and increase the output voltage of the bridge circuit,
the first magnetoresistive effect element 11 is more preferably a
TMR element.
[0068] FIG. 4B is a plan view showing the schematic composition of
the magnetoresistive effect element (first magnetoresistive effect
element 11) shown in FIG. 4A when viewed from the free layer 46
side. FIG. 5A is a schematic diagram conceptually showing the
magnetization of the free layer 46 in a state in which an external
magnetic field is not applied. FIG. 5B is a schematic diagram
conceptually showing the magnetization of the pinned layer 42 in a
state in which an external magnetic field is not applied. Arrows in
FIG. 5A and FIG. 5B schematically show the magnetization
directions.
[0069] The free layer 46 is magnetized in an initial magnetization
direction D1 substantially parallel to the lengthwise direction in
the plan view through the bias magnetic field of the bias magnets
47. The initial magnetization direction D1 of the free layer 46 is
substantially parallel to the magnetization direction D2 of the
bias magnets 47. The pinned layer 42 is magnetized in a
magnetization direction D3 substantially parallel to the short
direction. When an external magnetic field in the short direction,
which is the magnetically sensitive direction of the free layer 46,
is applied, the magnetization of the free layer 46 rotates
clockwise or anticlockwise in FIG. 4B in accordance with the
strength of the external magnetic field. Through this, the relative
angle between the magnetization direction D3 of the pinned layer 42
and the magnetization direction of the free layer 46 changes, and
the electrical resistance to the sense electric current
changes.
[0070] As shown in FIG. 3A, the initial magnetization direction D1
of the free layer 46 in the first through fourth magnetoresistive
effect elements 11.about.14 is the lengthwise direction of the free
layer 46. The magnetization direction D3 of the pinned layers 42 of
the first magnetoresistive effect element 11 and the third
magnetoresistive effect element 13 is the short direction of the
pinned layer 42, and the magnetization direction D3 of the pinned
layers 42 of the second magnetoresistive effect element 12 and the
fourth magnetoresistive effect element 14 is antiparallel to the
magnetization direction D3 of the pinned layers 42 of the first
magnetoresistive effect element 11 and the third magnetoresistive
effect element 13. Accordingly, when an external magnetic field in
the magnetization direction D3 of the pinned layers 42 of the first
magnetoresistive effect element 11 and the third magnetoresistive
effect element 13 is applied, the electrical resistance of the
first magnetoresistive effect element 11 and the third
magnetoresistive effect element 13 decreases, and the electrical
resistance of the second magnetoresistive effect element 12 and the
fourth magnetoresistive effect element 14 increases. Through this,
the midpoint voltage V1 increases and the midpoint voltage V2
decreases, as shown in FIG. 3B. On the other hand, when an external
magnetic field in the magnetization direction D3 of the pinned
layers 42 of the second magnetoresistive effect element 12 and the
fourth magnetoresistive effect element 14 is applied, the midpoint
voltage V1 decreases and the midpoint voltage V2 increases. By
detecting the difference (V1-V2) between the midpoint voltage V1
and the midpoint voltage V2, twice the sensitivity can be obtained
compared to detecting the midpoint voltage V1 and the midpoint
voltage V2. In addition, even if the midpoint voltage V1 and the
midpoint voltage V2 in FIG. 3B shift (offset) in the same direction
(for example, upwards in the graph in FIG. 3B), by detecting the
difference (V1-V2) between the midpoint voltage V1 and the midpoint
voltage V2, it is possible to exclude the effects of the
offset.
[0071] When stress in a prescribed direction is applied on the
first through fourth magnetoresistive effect elements 11.about.14,
the initial magnetization direction D1 of the free layer 46 rotates
due to an inverse magnetostrictive effect. FIG. 3C is a schematic
drawing showing a state in which a tensile stress S is applied at a
45.degree. angle with respect to the lengthwise direction of the
free layer 46 of the first through fourth magnetoresistive effect
elements 11.about.14. The inverse magnetostrictive effect acts in
different directions depending on whether the magnetostrictive
constant is negative or positive and whether the stress is a
tensile stress S or a compression stress. When the magnetostrictive
constant of the free layer 46 on which a tensile stress is applied
is positive, and when the magnetostrictive constant of the free
layer 46 on which a compression stress is applied is negative, the
initial magnetization direction D1 of the free layer 46 rotates to
a direction parallel to the stress. When the magnetostrictive
constant of the free layer 46 on which the tensile stress S is
applied is negative, and when the magnetostrictive constant of the
free layer 46 on which a compression stress is applied is positive,
the initial magnetization direction D1 of the free layer 46 rotates
to a direction orthogonal to the stress. As shown in FIG. 3C, when
the tensile stress S is applied at a 45.degree. angle, the
magnetostrictive constant of the free layer 46 becomes negative and
the initial magnetization direction D1 of the free layers 46 of the
first magnetoresistive effect element 11 and the third
magnetoresistive effect element 13 rotates to the orientation of
the magnetization direction D3 of the pinned layer 42, so the
electrical resistance of the first magnetoresistive effect element
11 and the third magnetoresistive effect element 13 decreases. The
initial magnetization direction D1 of the free layer 46 of the
second magnetoresistive effect element 12 and the fourth
magnetoresistive effect element 14 rotates to the opposite
direction of the magnetization direction D3 of the pinned layer 42,
so the electrical resistance of the second magnetoresistive effect
element and the fourth magnetoresistive effect element 14
increases. Through this, as shown in FIG. 3D, the midpoint voltage
V1 increases and the midpoint voltage V2 decreases, so the
difference (V1-V2) between the midpoint voltage V1 and the midpoint
voltage V2 increases. That is, through the external stress, the
above-described difference (V1-V2) that is the output of the
magnetic sensor 1 when no external magnetic field is applied is
offset from zero. There is concern that the offset of the output
(the above-described difference V1-V2) could affect the detection
accuracy of the magnetic sensor 1.
[0072] The external stress can occur due to a force received from
the resin or the like used for sealing when the magnetic sensor tip
2 is enclosed by resin, for example. Stress can also occur in
procedures (for example, soldering procedures) when mounting the
magnetic sensor 1 in which the magnetic sensor tip 2 is sealed in
the sealed part 3 on a substrate to form a module.
[0073] Stress can arise in procedures (for example, screwing
procedures) when the module is incorporated into a product, and
even when used as a product, thermal stress can arise through
temperature changes, for example. Such stress is difficult to
predict and measure and is also difficult to control. Accordingly,
what is essentially desired is for the output (the above-described
difference V1-V2) of the magnetic sensor 1 to not be affected by
external stress.
[0074] FIG. 6 is a plan view showing the positional relationship
between the magnetization direction of the pinned layer 42 and the
sealed part 3 and magnetic sensor tip 2 of the magnetic sensor
according to this embodiment. As shown in FIG. 6, in the magnetic
sensor 1 according to this embodiment, the magnetization direction
of the pinned layer 42 is inclined with respect to the
approximately straight line 7 found through the least squares
method using a plurality of points arbitrarily set on the first
side 31 of the sealed part 3. Through this, it is possible to
reduce the stress sensitivity of the magnetic sensor 1, and to
realize the effect of improving offset properties. In this
embodiment, an arbitrary plurality of points was set on the first
side 31 in order to find the approximately straight line 7, but
this is intended to be illustrative and not limiting, for the
approximately straight line 7 may be found by setting a plurality
of points arbitrarily on any one of the sides out of the first side
31, the second side 32, the third side 33 and the fourth side
34.
[0075] In the magnetic sensor 1 according to this embodiment, the
lengthwise direction of the pinned layer 42 of the first through
fourth magnetoresistive effect elements 11.about.14 is inclined
with respect to the first side 21 of the magnetic sensor tip 2, and
the first side 21 of the magnetic sensor tip 2 and the
above-described approximately straight line 7 found through the
least squares method using a plurality of points arbitrarily set on
the first side 31 of the sealed part 3 are substantially parallel,
and through this the magnetization direction of the pinned layer 42
may be inclined with respect to the above-described approximately
straight line 7 (see FIG. 6). In this embodiment, the state shown
in FIG. 6 is intended to be illustrative and not limiting, for the
magnetization direction of the pinned layer 42 may be caused to
incline with respect to the above-described approximately straight
line 7 by making the lengthwise or short direction of the pinned
layer 42 of the first through fourth magnetoresistive effect
elements 11.about.14 and the first side 21 of the magnetic sensor
tip 2 be substantially parallel and by causing the first side 21 of
the magnetic sensor tip 2 to be inclined with respect to the
above-described approximately straight line 7 found through the
least squares method using a plurality of points arbitrarily set on
the first side 31 of the sealed part 3 (see FIG. 7).
[0076] FIGS. 8A.about.C are graphs showing the output voltages V1
and V2 with respect to external stress when the magnetization
direction of the pinned layer 42 is inclined at 0.degree.,
10.degree., 20.degree., 30.degree. and 45.degree. respectively,
with respect to the approximately straight line 7 of the magnetic
sensor 1 shown in FIG. 6, and the change in the difference (V1-V2)
of the outputs. In the magnetic sensor 1 in a state in which the
pinned layer 42 is at 0.degree., that is to say substantially
parallel, to the approximately straight line 7, the voltage offset
of the output voltage V1 increases in the negative direction (see
FIG. 8A) and the voltage offset of the output V2 increases in the
positive direction (see FIG. 8B) when an external stress is applied
at 45.degree.. Consequently, the voltage offset of the difference
(V1-V2) of the outputs increases in the negative direction (see
FIG. 8C), and the effect of the external stress is greatly
received. In the magnetic sensor 1 in a state in which the
magnetization direction of the pinned layer 42 is inclined at
10.degree., 20.degree. and 30.degree., respectively, with respect
to the approximately straight line 7, the amount of increase of the
difference (V1-V2) of the outputs in the negative direction can be
diminished as the angle of the magnetization direction of the
pinned layer 42 becomes larger (see FIG. 8C). Furthermore, in the
magnetic sensor 1 in which the magnetization direction of the
pinned layer 42 is inclined at a 45.degree. angle with respect to
the approximately straight line 7, the output V1 increases in the
positive direction (see FIG. 8A) and V2 increases in the negative
direction (see FIG. 8B), so the voltage offset of the difference
(V1-V2) of the outputs is virtually completely suppressed.
[0077] FIGS. 9A.about.C are graphs showing the output voltages V1
and V2 with respect to external stress when the magnetization
direction of the pinned layer 42 is inclined at 90.degree.,
80.degree., 70.degree., 60.degree. and 45.degree. respectively,
with respect to the approximately straight line 7 of the magnetic
sensor 1 shown in FIG. 6, and the change in the difference (V1-V2)
of the outputs. In the magnetic sensor 1 in a state in which the
pinned layer 42 is at 90.degree., that is, substantially
orthogonal, to the approximately straight line 7, the voltage
offset of the output voltage V1 increases in the positive direction
(see FIG. 9A) and the voltage offset of the output V2 increases in
the negative direction (see FIG. 9B) when an external stress is
applied at 45.degree.. Consequently, the voltage offset of the
difference (V1-V2) of the outputs increases in the positive
direction (see FIG. 9C), and the effect of the external stress is
greatly received. In the magnetic sensor 1 in a state in which the
magnetization direction of the pinned layer 42 is inclined at
80.degree., 70.degree. and 60.degree., respectively, with respect
to the approximately straight line 7, the amount of increase of the
difference (V1-V2) of the outputs in the positive direction can be
diminished as the angle of the magnetization direction of the
pinned layer 42 becomes smaller (see FIG. 9C). Furthermore, in the
magnetic sensor 1 in which the magnetization direction of the
pinned layer 42 is inclined at a 45.degree. angle with respect to
the approximately straight line 7, the voltage offset of the
difference (V1-V2) of the outputs is virtually completely
suppressed.
[0078] As shown in FIGS. 8A.about.C and FIG. 9A.about.C, by causing
the magnetization direction of the pinned layer 42 to be inclined
with respect to the approximately straight line 7 in a state in
which an external magnetic field is not applied on the
magnetoresistive effect element, it is possible to diminish the
stress sensitivity and to reduce fluctuations in voltage offset.
The angle of inclination of the pinned layer 42 is not particularly
restricted as long as such is within a range capable of reducing
fluctuation in the voltage offset, and inclination within a range
of 10.about.80.degree. with respect to the approximately straight
line 7 is particularly preferable.
[0079] The magnetic sensor 1 described above can be used in an
electric current sensor, for example. FIG. 10A is a schematic end
view of an electric current sensor equipped with the magnetic
sensor 1, and FIG. 10B is a cross-sectional view along line A-A in
FIG. 10A. The magnetic sensor 1 is positioned near an electric
current line 102 and causes generation of a magnetoresistive change
in accordance with change in a signal magnetic field Bs that is
applied. An electric current sensor 101 has a first soft magnetic
material 103 and a second soft magnetic material 104, for adjusting
the magnetic field strength, and a solenoid-type feedback coil 105,
which is provided near the magnetic sensor 1.
[0080] The feedback coil 105 causes generation of a magnetic field
Bc that cancels the signal magnetic field Bs. The feedback coil 105
is wound in a spiral shape around the magnetic sensor 1 and the
second soft magnetic material 104. An electric current i flows in
the electric current line 102 from the front side of the paper to
the back side in FIG. 10A and from left to right in FIG. 10B.
Through this electric current i, a clockwise external magnetic
field Bo is induced in FIG. 10A. The external magnetic field Bo is
mitigated by the first soft magnetic material 103, is amplified by
the second soft magnetic material 104 and is applied leftward on
the magnetic sensor 1 as the signal magnetic field Bs. The magnetic
sensor 1 outputs a voltage signal corresponding to the signal
magnetic field Bs, and this voltage signal is input into the
feedback coil 105. In the feedback coil 105, the feedback electric
current Fi flows, and the feedback electric current Fi generates a
cancel magnetic field Bc that cancels the signal magnetic field Bs.
Because the signal magnetic field Bs and the cancel magnetic field
Bc have the same absolute value but are opposite in direction, the
signal magnetic field Bs is offset by the cancel magnetic field Bc,
so that the magnetic field that is applied on the magnetic sensor 1
become substantially zero. The feedback electric current Fi is
converted into a voltage by a resistor (undepicted) and is output
as a voltage value. The voltage value is proportional to the
feedback electric current Fi, the cancel magnetic field Bc and the
signal magnetic field Bs, so it is possible to obtain an electric
current that flows in the electric current line 102 from the
voltage value.
[0081] The above-described embodiment was described in order to
facilitate understanding of the present invention and was not
described to limit the present invention. Accordingly, all
components disclosed in the above-described embodiment shall be
construed to include all design modifications and equivalents
falling within the technical scope of the present invention.
[0082] In the above-described embodiment, the multilayer film 40
that makes up the magnetoresistive effect elements was described by
taking as an example one that includes the antiferromagnetic layer
41, the pinned layer 42, the spacer layer 45 and the free layer 46,
but this is intended to be illustrative and not limiting, for it
would be fine to include a nonmagnetic intermediate layer 43 and a
reference layer 44 between the pinned layer 42 and the spacer layer
45, for example (see FIG. 11). The reference layer 44 is a
ferromagnetic layer interposed between the pinned layer 42 and the
spacer layer 45, is magnetically coupled with the pinned layer 42
via the nonmagnetic intermediate layer 43 made of Ru, Rh or the
like, and more specifically is antiferromagnetically coupled with
the pinned layer 42. Accordingly, the reference layer 44 and the
pinned layer 42 both have magnetization directions fixed with
respect to the external magnetic field, and the magnetization
directions thereof are in orientations antiparallel to each other.
Through this, even when the magnetization direction of the
reference layer 44 stabilizes, the magnetic field discharged from
the reference layer 44 is canceled by the magnetic field discharged
from the pinned layer 42, so that it is possible to suppress any
magnetic field leakage to the outside. In this case, the
magnetization direction of the reference layer 44 can be inclined
with respect to the approximately straight line 7.
EMBODIMENTS
[0083] Below, the present invention will be described in greater
detail through embodiments, but the present invention is in no way
limited by the below-described embodiments or the like.
Embodiment 1
[0084] A magnetic sensor 1 having the configuration shown in FIG. 6
and with the magnetization direction of the pinned layer 42 with
respect to the approximately straight line 7 being 45.degree. was
prepared, and the changes in the outputs V1 and V2 of the magnetic
sensor 1 and the difference (V1-V2) of the outputs in a state in
which the tensile stress S (see FIG. 3C) was applied on the
magnetic sensor 1 were measured. The state in which the tensile
stress S was applied on the magnetic sensor 1 was realized through
the simulated load method described below.
[0085] FIGS. 12A.about.12C are drawings describing the simulated
load addition method of the magnetic sensor. First, the magnetic
sensor 1 is fixed to a substrate 51 through soldering of the lead
wires 5 (see FIG. 12A). Next, a plate 52 is pressed in the +Z
direction against the back surface (surface on the side opposite
the surface to which the magnetic sensor 1 is fixed) side of the
substrate 51 (see FIG. 12B). Because the substrate 51 curves so
that the front surface (the surface to which the magnetic sensor 1
is fixed) side becomes convex, the lead wires 5 deform to spread to
the outside. Through this, it is possible to apply the tensile
stress S on the magnetic sensor 1 via the lead wires 5. FIG. 12C is
a top view of when the plate 52 is pressed against the substrate 51
at a 45.degree. angle with respect to the approximately straight
line 7 in the plan view from the +Z direction side of FIG. 12B, and
through this, application of the tensile stress S (the tensile
stress S at a 45.degree. angle with respect to the approximately
straight line 7) shown in FIG. 3C was realized.
[0086] In Embodiment 1, the plate 52 was pressed against the
substrate 51 at 0.degree., 45.degree. and 90.degree. angles with
respect to the approximately straight line 7, and the change in the
outputs V1 and V2 and the difference (V1-V2) of the outputs was
measured when the +Z direction displacement D of the substrate 51
was caused to change. Results are shown in FIGS. 13A.about.13C. In
the graphs shown in FIGS. 13A 13C, the horizontal axis indicates
the displacement D (mm) and the vertical axis indicates the voltage
offset (mV/V). The voltage offset is found as the difference
between the outputs V1 and V2 and the difference (V1-V2) of the
outputs of the magnetic sensor 1 in a state in which the tensile
stress S is not applied, and the outputs V1 and V2 and the
difference (V1-V2) of the outputs of the magnetic sensor 1 in a
state in which the tensile stress S is applied.
Embodiment 2
[0087] Using the same load addition method as Embodiment 1 (see
FIGS. 12A.about.12C), the tensile stress S was applied by pressing
the plate 52 on the substrate 51 at 0.degree., 45.degree. and
90.degree. angles against the magnetic sensor 1 having the
configuration shown in FIG. 7 and in which the angle of inclination
of the first side 21 of the magnetic sensor tip 2 with respect to
the approximately straight line 7 was 45.degree., and changes in
the outputs V1 and V2 and the difference (V1-V2) of the outputs
when the +Z displacement D of the substrate 51 was caused to change
were measured. Results are shown in FIGS. 14A.about.14C. In the
graphs shown in FIGS. 14A.about.14C, the horizontal axis indicates
the displacement D (mm) and the vertical axis indicates the voltage
offset (mV/V). The voltage offset is found as the difference
between the outputs V1 and V2 and the difference (V1-V2) of the
outputs of the magnetic sensor 1 in a state in which the tensile
stress S is not applied, and the outputs V1 and V2 and the
difference (V1-V2) of the outputs of the magnetic sensor 1 in a
state in which the tensile stress S is applied.
Comparison Example 1
[0088] A magnetic sensor 1' having the configuration shown in FIG.
15A was prepared. FIG. 15A is a plan view of the magnetic sensor 1'
of Comparison Example 1. In the magnetic sensor 1' shown in FIG.
15A, in the plan view from a first surface 3a' side of a sealed
part 3', the magnetization direction of a pinned layer 42' is
substantially orthogonal to an approximately straight line 7'
calculated through the least squares method using a plurality of
points arbitrarily set on a first side 31' the sealed part 3'
has.
[0089] Using the same load addition method as Embodiment 1 (see
FIGS. 12A.about.12C), the tensile stress S was applied by pressing
the plate 52 on the substrate 51 at 0.degree., 45.degree. and
90.degree. angles against the magnetic sensor 1' having the
configuration shown in FIG. 15A, and changes in the outputs V1 and
V2 and the difference (V1-V2) of the outputs when the +Z
displacement D of the substrate 51 was caused to change were
measured. Results are shown in FIGS. 16A.about.16C. In the graphs
shown in FIGS. 16A.about.16C, the horizontal axis indicates the
displacement D (mm) and the vertical axis indicates the voltage
offset (mV/V). The voltage offset is found as the difference
between the outputs V1 and V2 and the difference (V1-V2) of the
outputs of the magnetic sensor 1' in a state in which the tensile
stress S is not applied, and the outputs V1 and V2 and the
difference (V1-V2) of the outputs of the magnetic sensor 1' in a
state in which the tensile stress S is applied.
Comparison Example 2
[0090] A magnetic sensor 1' having the configuration shown in FIG.
15B was prepared. FIG. 15B is a plan view of the magnetic sensor 1'
of Comparison Example 2. In the magnetic sensor 1' shown in FIG.
15B, when a magnetic sensor tip 2' is viewed from a first surface
3a' side of a sealed part 3', the magnetization direction of a
pinned layer 42' in a state in which the external magnetic field is
not applied on the magnetoresistive effect element is substantially
parallel to a first side 21' of the magnetic sensor tip 2'.
[0091] Using the same load addition method as Embodiment 1 (see
FIGS. 12A.about.12C), the tensile stress S was applied by pressing
the plate 52 on the substrate 51 at 0.degree., 45.degree. and
90.degree. angles against the magnetic sensor 1' having the
configuration shown in FIG. 15B, and changes in the outputs V1 and
V2 and the difference (V1-V2) of the outputs when the +Z
displacement D of the substrate 51 was caused to change were
measured. Results are shown in FIGS. 17A.about.17C. In the graphs
shown in FIGS. 17A.about.17C, the horizontal axis indicates the
displacement D (mm) and the vertical axis indicates the voltage
offset (mV/V). The voltage offset is found as the difference
between the outputs V1 and V2 and the difference (V1-V2) of the
outputs of the magnetic sensor 1' in a state in which the tensile
stress S is not applied, and the outputs V1 and V2 and the
difference (V1-V2) of the outputs of the magnetic sensor 1' in a
state in which the tensile stress S is applied.
[0092] In the magnetic sensors of Comparison Example 1 and
Comparison Example 2, it was confirmed that fluctuations in the
voltage offset when the tensile stress S is applied at 0.degree.
and 90.degree. angles is small (see FIG. 16A, FIG. 16C, FIG. 17A
and FIG. 17C), but when the tensile stress S is applied at a
45.degree. angle, the displacement D increases and accordingly the
voltage offset became large (see FIG. 16B and FIG. 17B). On the
other hand, in the magnetic sensor of Embodiment 1, it was
confirmed that fluctuations in the voltage offset when the tensile
stress S was applied at 0.degree. and 90.degree. angles was small,
similar to Comparison Example 1 and Comparison Example 2 (see FIG.
13A and FIG. 13C), but when the tensile stress S is applied at a
45.degree. angle, fluctuations in the voltage offset were
suppressed more than in Comparison Example 1 and Comparison Example
2 (see FIG. 13B).
[0093] In addition, in the magnetic sensor of Embodiment 2, it was
confirmed that fluctuations in voltage offset were suppressed more
than in Comparison Example 1 and Comparison Example 2 (see FIGS.
14A, 14B) when the tensile stress S was applied at 0.degree. and
450 angles. On the other hand, when the tensile stress S was
applied at a 90.degree. angle, it was confirmed that the
displacement D increases and accordingly the voltage offset becomes
larger (see FIG. 14C). From this, it can be said that when the
direction (angle) at which external stress is applied in accordance
with the application or the like of the magnetic sensor is known,
it is possible to optimize placement of the magnetic sensor tip 2
inside the magnetic sensor 1 in accordance thereto. The reason the
voltage offset becomes larger when the tensile stress S is applied
at a 90.degree. angle is conjectured to be because by having the
first side 21, the second side 22, the third side 23 and the fourth
side 24 possessed by the magnetic sensor tip 2 be inclined at a
45.degree. angle with respect to the applied tensile stress S, the
influence of the tensile stress S applied on the magnetic sensor
tip 2 becomes large so the voltage offset becomes large.
DESCRIPTION OF SYMBOLS
[0094] 1 Magnetic sensor [0095] 2 Magnetic sensor tip [0096] 21
First side [0097] 3 Sealed part [0098] 31 First side [0099] 7
Approximately straight line [0100] 11.about.14 First through fourth
magnetoresistive effect elements [0101] 41 Antiferromagnetic layer
[0102] 42 Pinned layer [0103] 43 Spacer layer [0104] 46 Free layer
[0105] 47 Bias magnet
* * * * *