JP2016166741A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic sensor that offers reduced variation of error in detected angle over a wide range of target magnetic field intensity.SOLUTION: A magnetic sensor is configured to generate an angle detection value having a corresponding relationship with an angle of direction of a target magnetic field with respect to a reference direction at a reference position. The magnetic sensor includes a magnetic field detection unit. When the direction of the target magnetic field rotates with a predetermined period, the angle detection value contains an angle error component that varies with a quarter of the predetermined period. A variation of a maximum value E4 of the angle error component, in absolute terms, shall be no greater than 0.1° when the target magnetic field intensity as measured by the magnetic field detection unit varies within a subrange, in a range of 20-150 mT, having upper and lower limits that differs by 30 mT or more.SELECTED DRAWING: Figure 21

Description

  The present invention relates to a magnetic sensor for detecting an angle formed by a direction of a detected magnetic field with respect to a reference direction.

  In recent years, magnetic sensors have been widely used to detect the rotational position of an object in various applications such as detection of the rotational position of an automobile steering. Magnetic sensors are used not only when detecting the rotational position of an object, but also when detecting a linear displacement of the object. In a system in which a magnetic sensor is used, a magnetic field generator that generates a detected magnetic field whose direction rotates in conjunction with the rotation or linear motion of an object is generally provided. The magnetic field generator is, for example, a magnet. The magnetic sensor uses a magnetic detection element to detect an angle formed by the direction of the detected magnetic field at the reference position with respect to the reference direction. As a result, the rotational position and linear displacement of the object are detected.

  As described in Patent Documents 1 and 2, a magnetic sensor having two bridge circuits (Wheatstone bridge circuits) is known. In this magnetic sensor, each of the two bridge circuits includes four magnetic detection elements, and outputs a signal corresponding to the direction of the detected magnetic field. The magnetic detection element includes a magnetoresistive element (hereinafter also referred to as an MR element). The phases of the output signals of the two bridge circuits differ by ¼ of the period of the output signal of each bridge circuit. The angle formed by the direction of the detected magnetic field with respect to the reference direction is calculated based on the output signals of the two bridge circuits.

Japanese Patent No. 5131339 JP-T-2004-504713

  In the magnetic sensor using the MR element, the waveform of the output signal of the MR element corresponding to the resistance value of the MR element is ideally a sine curve (Sine waveform) as the direction of the detected magnetic field rotates. Cosine waveform). However, as described in Patent Document 1, it is known that the output signal waveform of the MR element may be distorted from a sine curve. The fact that the output signal waveform of the MR element is distorted from the sinusoidal curve means that the output signal of the MR element contains harmonic components other than the fundamental wave of the sinusoidal curve. If the output signal of the MR element contains a harmonic component, an error may occur in the detection angle by the magnetic sensor.

  Hereinafter, the MR element includes a magnetization fixed layer whose magnetization direction is fixed, a free layer whose magnetization direction changes according to the direction of the detected magnetic field, and a nonmagnetic layer disposed between the magnetization fixed layer and the free layer An example of a case where the output signal waveform of the MR element is distorted will be described, taking as an example the case of a spin valve MR element having the above. Examples of the spin valve MR element include a GMR (giant magnetoresistive effect) element and a TMR (tunnel magnetoresistive effect) element. Examples of the case where the output signal waveform of the MR element is distorted include the case where the magnetization direction of the magnetization fixed layer fluctuates due to the influence of the detected magnetic field or the like, or the magnetization direction of the free layer is influenced by the shape anisotropy of the free layer, etc. Depending on the case, the direction of the detected magnetic field may not match.

  Patent Document 1 describes a technique for reducing an error in detection angle as follows. In this technique, a bridge circuit is configured by replacing a conventional spin-valve MR element constituting a bridge circuit with an MR element array composed of a plurality of spin-valve MR elements connected in series. The MR element array includes one or more pairs of MR elements. The magnetization direction of the magnetization fixed layer in the two MR elements constituting the pair is a direction rotated by the same angle in the opposite direction with respect to the magnetization direction of the magnetization fixed layer in the MR element constituting the conventional bridge circuit. .

  In Patent Document 2, two correction detection elements each having a reference magnetization axis inclined with respect to the main reference magnetization axis are electrically connected to a main detection element having a main reference magnetization axis to correct the detection angle. The technology is described.

  By the way, in the course of research by the inventors of the present application, it has been found that in the magnetic sensor, the error in the detection angle changes according to the strength of the detected magnetic field. Hereinafter, the error of the detected angle is referred to as an angle error, and the change of the angle error according to the strength of the detected magnetic field is referred to as the dependence of the angle error on the magnetic field strength. The dependence of the angle error on the magnetic field strength also exists in a magnetic sensor provided with a means for reducing the error in the detection angle.

  On the other hand, in a system using a magnetic sensor, the intensity of the detected magnetic field applied to the magnetic sensor is not always constant. For example, it is possible to combine a plurality of types of magnetic field generators having different detected magnetic field strengths with the same magnetic sensor. Further, when a magnet is used as the magnetic field generator, the strength of the detected magnetic field may change due to temperature change or deterioration of the magnet without changing the magnet. In addition, when an inexpensive magnet is used, the actual detected magnetic field strength may be different from the strength assumed in the system design stage.

  In conventional magnetic sensors, due to the above-mentioned dependence of the angle error on the magnetic field strength, the amount of fluctuation of the angle error is large within a predetermined range assumed as the range of the detected magnetic field strength when using the magnetic sensor. was there. In this case, in the conventional magnetic sensor, even if the detection angle is corrected so that the angle error is reduced when the intensity of the detected magnetic field is a specific value within the predetermined range, the intensity of the detected magnetic field When is different from the above specific value, there is a problem that the angle error is not sufficiently reduced.

  The present invention has been made in view of such problems, and an object of the present invention is a magnetic sensor for detecting an angle formed by the direction of a detected magnetic field with respect to a reference direction, and a wide range of the intensity of the detected magnetic field. Thus, it is an object of the present invention to provide a magnetic sensor with a small variation in detection angle error.

  The magnetic sensor of the present invention generates an angle detection value having a correspondence relationship with the angle formed by the direction of the detected magnetic field at the reference position with respect to the reference direction, and includes a magnetic field detection unit and a calculation unit. . The magnetic field detection unit includes a plurality of magnetoresistive elements that detect the detected magnetic field, and the direction of the detected signal and the first signal having a correspondence relationship with the angle formed by the direction of the detected magnetic field with respect to the first direction Outputs a second signal having a corresponding relationship with the angle formed by the second direction. Each of the plurality of magnetoresistive elements is disposed between a magnetization fixed layer whose magnetization direction is fixed, a free layer whose magnetization direction changes according to the direction of the detected magnetic field, and between the magnetization fixed layer and the free layer. And a nonmagnetic layer. The calculation unit calculates an angle detection value based on the first and second signals.

  In the magnetic sensor of the present invention, when the direction of the detected magnetic field rotates at a predetermined cycle, the angle detection value includes an angle error component that changes at a quarter of the predetermined cycle. In the magnetic sensor of the present invention, the intensity of the magnetic field to be detected in the magnetic field detector is a sub-range that is part of the range of 20 to 150 mT, and changes within the sub-range in which the difference between the upper limit and the lower limit is 30 mT or more. The fluctuation amount of the absolute value of the absolute value of the angle error component is 0.1 ° or less.

  In the magnetic sensor of the present invention, when the direction of the magnetic field to be detected rotates with a predetermined period, the first signal includes a first ideal component that periodically changes to draw an ideal sine curve, and the first signal The first third harmonic component, which is an error component corresponding to the third harmonic with respect to the ideal component, and the first fifth harmonic component, which is an error component corresponding to the fifth harmonic with respect to the first ideal component The second signal includes a second ideal component that periodically changes to draw an ideal sine curve, and an error component corresponding to a third harmonic with respect to the second ideal component. And a second third harmonic component that is an error component corresponding to the fifth harmonic with respect to the second ideal component.

  Further, the ratio of the first third harmonic component to the first ideal component when the first ideal component has the maximum value is set as the first ratio, and the first ideal component has the maximum value when the first ideal component has the maximum value. The ratio of the first fifth harmonic component to one ideal component is the second ratio, and the ratio of the second third harmonic component to the second ideal component when the second ideal component takes the maximum value Is the third ratio, the ratio of the second fifth harmonic component to the second ideal component when the second ideal component takes the maximum value is the fourth ratio, and the first ratio and the third ratio When the average value of the ratio is the third harmonic component ratio and the average value of the second ratio and the fourth ratio is the fifth harmonic component ratio, the intensity of the detected magnetic field in the magnetic field detector is within the sub-range. The fluctuation amount of the absolute value of the difference between the third harmonic component ratio and the fifth harmonic component ratio when changing at It may be.

  In the magnetic sensor of the present invention, the calculation unit includes an angle detection value calculation unit that calculates an angle detection value, and a correction processing unit that performs correction processing on the angle detection value to generate a corrected angle detection value. May be included. The maximum absolute value of the error in the detected angle value after correction is smaller than the maximum absolute value of the error in the detected angle value. In this case, the correction processing unit sets the difference between the maximum value and the minimum value of the corrected angle detection value to 0, regardless of the value of the detected magnetic field strength in the sub-range in the magnetic field detection unit. Correction processing may be performed so that the angle is 1 ° or less.

  In the magnetic sensor of the present invention, the amount of change in the maximum absolute value of the angle error component when the intensity of the detected magnetic field in the magnetic field detector changes within the sub-range is 0.05 ° or less. Good. In this case, when the intensity of the magnetic field to be detected in the magnetic field detection unit changes within the sub-range, the variation amount of the absolute value of the difference between the third harmonic component ratio and the fifth harmonic component ratio is 0.09% or less. It may be. The calculation unit may include an angle detection value calculation unit that calculates an angle detection value and a correction processing unit that performs a correction process on the angle detection value to generate a corrected angle detection value. The maximum absolute value of the error in the detected angle value after correction is smaller than the maximum absolute value of the error in the detected angle value. In this case, the correction processing unit sets the difference between the maximum value and the minimum value of the corrected angle detection value to 0, regardless of the value of the detected magnetic field strength in the sub-range in the magnetic field detection unit. Correction processing may be performed so that the angle is .05 ° or less.

  In the magnetic sensor of the present invention, the second direction may be orthogonal to the first direction.

  In the magnetic sensor of the present invention, the magnetic field detection unit may include a first detection circuit that outputs a first signal and a second detection circuit that outputs a second signal. Each of the first detection circuit and the second detection circuit may include a magnetoresistive element array formed by connecting two or more of the plurality of magnetoresistive elements in series. Each free layer of the plurality of magnetoresistive elements has a first surface in contact with the nonmagnetic layer and a second surface opposite to the first surface. The second surface has a four-fold rotational symmetry shape that is not five or more times rotationally symmetric. The number of the two or more magnetoresistive elements constituting the magnetoresistive element array is an even number. The two or more magnetoresistive effect elements constituting the magnetoresistive effect element array include one or more pairs of magnetoresistive effect elements. The magnetization direction of the magnetization fixed layer in the two magnetoresistive effect elements constituting the pair forms a predetermined relative angle excluding 0 ° and 180 °. In the first detection circuit, the first direction is an intermediate direction of the magnetization direction of the magnetization fixed layer in the two magnetoresistive effect elements constituting the pair or a direction opposite thereto. In the second detection circuit, the second direction is an intermediate direction of the magnetization direction of the magnetization fixed layer in the two magnetoresistive effect elements constituting the pair or a direction opposite thereto.

  In the magnetic sensor of the present invention, the fluctuation amount of the maximum value of the absolute value of the angle error component when the intensity of the magnetic field to be detected in the magnetic field detector changes within the above subrange is 0.1 ° or less. Thus, according to the present invention, there is an effect that it is possible to reduce the fluctuation amount of the detection angle error in a wide range of the detected magnetic field intensity.

1 is a perspective view showing a schematic configuration of a magnetic sensor system including a magnetic sensor according to an embodiment of the present invention. It is explanatory drawing which shows the definition of the direction and angle in one embodiment of this invention. It is a circuit diagram which shows the structure of the magnetic sensor which concerns on one embodiment of this invention. It is a functional block diagram which shows the structure of the calculating part in the magnetic sensor shown in FIG. It is explanatory drawing which shows the relationship of the magnetization direction of the magnetization fixed layer of the two MR elements which comprise a pair in the magnetic sensor shown in FIG. It is a top view which shows one Wheatstone bridge circuit shown in FIG. It is a perspective view which shows a part of one magnetic detection element in FIG. It is a wave form diagram which shows the 1st example of the relationship between a some error component and an angle error quaternary component. It is a wave form diagram which shows the 2nd example of the relationship between a some error component and an angle error quaternary component. It is a wave form diagram which shows the 3rd example of the relationship between a some error component and an angle error quaternary component. It is a wave form diagram which shows the 4th example of the relationship between a some error component and an angle error quaternary component. It is a characteristic view showing the relationship between the absolute value of the difference between the third harmonic component ratio and the fifth harmonic component ratio and the maximum absolute value of the angular error quaternary component. It is explanatory drawing for demonstrating the shape of the 2nd surface of the free layer of MR element in one embodiment of this invention. It is explanatory drawing for demonstrating the shape of the 2nd surface of the free layer of MR element in one embodiment of this invention. It is explanatory drawing for demonstrating the shape of the 2nd surface of the free layer of MR element in one embodiment of this invention. FIG. 11 is a characteristic diagram showing changes in the magnetic field strength dependence of the third harmonic component ratio and the fifth harmonic component ratio when the shape of the second surface of the free layer of the MR element is changed. It is a characteristic view showing a change in the magnetic field strength dependency of the maximum value of the absolute value of the angular error quaternary component when the shape of the second surface of the free layer of the MR element is changed. It is a characteristic view which shows the change of the magnetic field strength dependence of each of the 3rd harmonic component ratio when changing an offset angle, and a 5th harmonic component ratio. It is a characteristic view which shows the change of magnetic field strength dependence of the maximum value of the absolute value of the angle error quaternary component when the offset angle is changed. It is a characteristic view which shows each magnetic field strength dependence of the 3rd harmonic component ratio in a 1st Example, and a 5th harmonic component ratio. It is a characteristic view which shows the magnetic field strength dependence of the maximum value of the absolute value of the angle error quaternary component in the first embodiment. It is a characteristic view which shows the angle error in a 1st Example. It is a characteristic view which shows the estimation angle error in a 1st Example. It is a characteristic view which shows the angle error after correction | amendment in a 1st Example. It is a characteristic view which shows the relationship between the applied magnetic field strength in 1st Example, and the amplitude of the angle error after correction | amendment. It is a characteristic view which shows each magnetic field strength dependence of the 3rd harmonic component ratio in a 2nd Example, and a 5th harmonic component ratio. It is a characteristic view which shows the magnetic field strength dependence of the maximum value of the absolute value of the angle error quaternary component in the second embodiment. It is a characteristic view which shows each magnetic field strength dependence of the 3rd harmonic component ratio in a 3rd Example, and a 5th harmonic component ratio. It is a characteristic view which shows the magnetic field strength dependence of the maximum value of the absolute value of the angle error quaternary component in the third embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a schematic configuration of a magnetic sensor system including a magnetic sensor according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a schematic configuration of a magnetic sensor system in the present embodiment. FIG. 2 is an explanatory diagram showing definitions of directions and angles in the present embodiment.

  As shown in FIG. 1, the magnetic sensor system in the present embodiment includes a magnetic sensor 1 according to the present embodiment and a magnetic field generator 2. The magnetic field generator 2 generates a detected magnetic field MF. In the example shown in FIG. 1, the magnetic field generator 2 is a cylindrical magnet. The magnetic field generation unit 2 has an N pole and an S pole that are arranged symmetrically about a virtual plane including the central axis of the cylinder. The magnetic field generator 2 rotates around the central axis of the cylinder. As a result, the direction of the detected magnetic field MF generated by the magnetic field generator 2 rotates around the rotation center C including the central axis of the cylinder.

  The magnetic sensor 1 detects an angle formed by the direction of the detected magnetic field MF at the reference position with respect to the reference direction. Specifically, the magnetic sensor 1 generates an angle detection value having a correspondence relationship with the angle formed by the direction of the detected magnetic field MF at the reference position with respect to the reference direction.

  The reference position is located in a virtual plane (hereinafter referred to as a reference plane) parallel to one end face of the magnetic field generator 2. In this reference plane, the direction of the detected magnetic field MF generated by the magnetic field generator 2 rotates around the reference position. The reference direction is located in the reference plane and intersects the reference position. In the following description, the direction of the detected magnetic field MF at the reference position refers to the direction located in the reference plane. In addition, simply referring to the direction of the detected magnetic field MF refers to the direction of the detected magnetic field MF at the reference position. The magnetic sensor 1 is disposed so as to face the one end face of the magnetic field generator 2.

  In addition, the structure of the magnetic sensor 1 and the magnetic field generation | occurrence | production part 2 is not restricted to the example shown in FIG. The magnetic sensor 1 and the magnetic field generator 2 only need to change the relative positional relationship between the magnetic sensor 1 and the magnetic field generator 2 so that the direction of the detected magnetic field MF rotates when viewed from the magnetic sensor 1. For example, in the magnetic sensor 1 and the magnetic field generation unit 2 arranged as shown in FIG. 1, the magnetic field generation unit 2 may be fixed and the magnetic sensor 1 may rotate, or the magnetic sensor 1 and the magnetic field generation unit 2 may be rotated. The magnetic sensor 1 and the magnetic field generator 2 may rotate in opposite directions, and may rotate at different angular velocities in the same direction.

  Further, as the magnetic field generating unit 2, a magnet in which one or more pairs of N poles and S poles are alternately arranged in a ring shape is used instead of the magnet shown in FIG. May be arranged. In this case, at least one of the magnet and the magnetic sensor 1 may be rotated.

  Further, as the magnetic field generator 2, instead of the magnet shown in FIG. 1, a magnetic scale in which a plurality of sets of N poles and S poles are alternately arranged in a straight line is used, and a magnetic sensor is provided in the vicinity of the outer periphery of the magnetic scale. 1 may be arranged. In this case, at least one of the magnetic scale and the magnetic sensor 1 may be moved linearly in the direction in which the N pole and the S pole of the magnetic scale are aligned.

  Also in the configuration of the various magnetic sensors 1 and the magnetic field generator 2 described above, there is a reference plane having a predetermined positional relationship with the magnetic sensor 1, and the direction of the detected magnetic field MF is within the reference plane within the reference plane. Rotate around the reference position as seen from the top.

  The magnetic sensor 1 includes a magnetic field detector 3. The magnetic field detection unit 3 includes a plurality of magnetic detection elements for detecting the detected magnetic field MF, and the first signal S1 having a correspondence relationship with the angle formed by the direction of the detected magnetic field MF with respect to the first direction and the detected signal A second signal S2 having a correspondence relationship with an angle formed by the direction of the magnetic field MF with respect to the second direction is output. Each of the plurality of magnetic detection elements includes at least one magnetoresistance effect element (hereinafter referred to as an MR element) that detects the detected magnetic field MF. Accordingly, the magnetic field detector 3 includes a plurality of MR elements.

  The magnetic field detection unit 3 includes a first detection circuit 10 and a second detection circuit 20. In FIG. 1, for ease of understanding, the first and second detection circuits 10 and 20 are depicted as separate bodies, but the first and second detection circuits 10 and 20 may be integrated. Good. In FIG. 1, the first and second detection circuits 10 and 20 are stacked in a direction parallel to the rotation center C, but the stacking order is not limited to the example shown in FIG.

  Here, with reference to FIG. 1 and FIG. 2, the definition of the direction and angle in this Embodiment is demonstrated. First, a direction parallel to the rotation center C shown in FIG. 1 and extending from bottom to top in FIG. 1 is defined as a Z direction. In FIG. 2, the Z direction is represented as a direction from the back to the front in FIG. Next, two directions perpendicular to the Z direction and orthogonal to each other are defined as an X direction and a Y direction. In FIG. 2, the X direction is represented as a direction toward the right side, and the Y direction is represented as a direction toward the upper side. In addition, a direction opposite to the X direction is defined as -X direction, and a direction opposite to the Y direction is defined as -Y direction.

  The reference position PR is a position where the magnetic sensor 1 detects the detected magnetic field MF. The reference direction DR is the X direction. The angle formed by the direction DM of the detected magnetic field MF with respect to the reference direction DR is represented by the symbol θ. The direction DM of the detected magnetic field MF is assumed to rotate counterclockwise in FIG. The angle θ is represented by a positive value when viewed counterclockwise from the reference direction DR, and is represented by a negative value when viewed clockwise from the reference direction DR.

  Next, the configuration of the magnetic sensor 1 will be described in detail with reference to FIG. FIG. 3 is a circuit diagram showing a configuration of the magnetic sensor 1. The magnetic sensor 1 includes a calculation unit 30 in addition to the magnetic field detection unit 3 described above. As described above, the magnetic field detection unit 3 includes the first detection circuit 10 and the second detection circuit 20.

  The first detection circuit 10 generates a first signal S1 having a correspondence relationship with an angle formed by the direction DM of the detected magnetic field MF with respect to the first direction. The second detection circuit 20 generates a second signal S2 having a correspondence relationship with an angle formed by the direction DM of the detected magnetic field MF with respect to the second direction. In the present embodiment, the first direction is the X direction, and the second direction is the Y direction. Therefore, the second direction is orthogonal to the first direction. In FIG. 2, an arrow with a symbol D <b> 1 represents a first direction, and an arrow with a symbol D <b> 2 represents a second direction. The first signal S1 is, for example, a signal corresponding to the intensity of the component in the first direction D1 (X direction) of the detected magnetic field MF at the reference position PR. The second signal S2 is, for example, a signal corresponding to the intensity of the component in the second direction D2 (Y direction) of the detected magnetic field MF at the reference position PR.

  When the direction DM of the detected magnetic field MF rotates with a predetermined period, both the first and second signals S1, S2 periodically change with a signal period T equal to the predetermined period. The phase of the second signal S2 is different from the phase of the first signal S1. In the present embodiment, the phase of the second signal S2 is preferably different from the phase of the first signal S1 by an odd multiple of 1/4 of the signal period T. However, the phase difference between the first signal S1 and the second signal S2 may be slightly deviated from an odd multiple of ¼ of the signal period T from the viewpoint of the accuracy of manufacturing the MR element. In the following description, it is assumed that the relationship between the phase of the first signal S1 and the phase of the second signal S2 is the above-described preferable relationship.

  The first detection circuit 10 has an output terminal that outputs the first signal S1. The second detection circuit 20 has an output terminal that outputs the second signal S2. The computing unit 30 has two input ends and one output end. Two input terminals of the arithmetic unit 30 are connected to output terminals of the first and second detection circuits 10 and 20, respectively.

  FIG. 4 is a functional block diagram illustrating a configuration of the calculation unit 30. The calculation unit 30 includes an angle detection value calculation unit 31, a correction processing unit 32, and a correction information holding unit 33. The angle detection value calculation unit 31 calculates an angle detection value θs having a corresponding relationship with the angle θ based on the first and second signals S1 and S2 output from the first and second detection circuits 10 and 20. To do. The correction processing unit 32 performs correction processing on the detected angle value θs to generate a corrected detected angle value θt. The maximum absolute value of the error of the corrected angle detection value θt is smaller than the maximum absolute value of the error of the angle detection value θs. The correction information holding unit 33 holds correction information used when the correction processing unit 32 performs correction processing. The corrected angle detection value θt is the value of the angle θ detected by the magnetic sensor 1. The arithmetic unit 30 can be realized by, for example, an application specific integrated circuit (ASIC) or a microcomputer. The calculation method of the angle detection value θs in the angle detection value calculation unit 31 and the content of the correction processing in the correction processing unit 32 will be described in detail later.

  As will be described in detail later, the calculation unit 30 does not include the correction processing unit 32 and the correction information holding unit 33, and outputs the angle detection value θs as the value of the angle θ detected by the magnetic sensor 1. Also good.

  The first detection circuit 10 includes a Wheatstone bridge circuit 14 and a difference detector 15. The Wheatstone bridge circuit 14 includes a power supply port V1, a ground port G1, two output ports E11 and E12, magnetic detection elements R11 and R12 connected in series, and magnetic detection elements R13 and R14 connected in series. Is included. One end of each of the magnetic detection elements R11 and R13 is connected to the power supply port V1. The other end of the magnetic detection element R11 is connected to one end of the magnetic detection element R12 and the output port E11. The other end of the magnetic detection element R13 is connected to one end of the magnetic detection element R14 and the output port E12. The other ends of the magnetic detection elements R12 and R14 are connected to the ground port G1. A power supply voltage having a predetermined magnitude is applied to the power supply port V1. The ground port G1 is connected to the ground. The difference detector 15 outputs the value of the signal corresponding to the potential difference between the output ports E11 and E12 to the arithmetic unit 30 as the first signal S1.

  The circuit configuration of the second detection circuit 20 is the same as that of the first detection circuit 10. That is, the second detection circuit 20 includes a Wheatstone bridge circuit 24 and a difference detector 25. The Wheatstone bridge circuit 24 includes a power supply port V2, a ground port G2, two output ports E21 and E22, magnetic detection elements R21 and R22 connected in series, and magnetic detection elements R23 and R24 connected in series. Is included. One end of each of the magnetic detection elements R21 and R23 is connected to the power supply port V2. The other end of the magnetic detection element R21 is connected to one end of the magnetic detection element R22 and the output port E21. The other end of the magnetic detection element R23 is connected to one end of the magnetic detection element R24 and the output port E22. The other ends of the magnetic detection elements R22 and R24 are connected to the ground port G2. A power supply voltage having a predetermined magnitude is applied to the power supply port V2. The ground port G2 is connected to the ground. The difference detector 25 outputs the value of the signal corresponding to the potential difference between the output ports E21 and E22 to the arithmetic unit 30 as the second signal S2.

  As described above, each of the plurality of magnetic detection elements included in the Wheatstone bridge circuits (hereinafter referred to as bridge circuits) 14 and 24 includes at least one MR element. In this embodiment, a spin valve MR element, particularly a TMR element is used as the MR element. A GMR element may be used instead of the TMR element. The spin-valve MR element includes a magnetization fixed layer whose magnetization direction is fixed, a free layer that is a magnetic layer whose magnetization direction changes according to the direction DM of the detected magnetic field MF, and between the magnetization fixed layer and the free layer. And a nonmagnetic layer. In the TMR element, the nonmagnetic layer is a tunnel barrier layer. In the GMR element, the nonmagnetic layer is a nonmagnetic conductive layer. In the spin valve MR element, the resistance value changes according to the angle formed by the magnetization direction of the free layer with respect to the magnetization direction of the magnetization fixed layer, and when this angle is 0 °, the resistance value becomes the minimum value. When the angle is 180 °, the resistance value becomes the maximum value.

  In the present embodiment, in particular, each of the plurality of magnetic detection elements included in the bridge circuits 14 and 24 is configured by an MR element array. The MR element array is configured by connecting two or more MR elements in series. The number of the two or more MR elements constituting the MR element array is an even number. Two or more MR elements constituting the MR element array include one or more pairs of MR elements. The magnetization direction of the magnetization fixed layer in the two MR elements constituting the pair has a predetermined relative angle excluding 0 ° and 180 °.

  In the first detection circuit 10, the first direction D1 is an intermediate direction of the magnetization direction of the magnetization fixed layer in the two MR elements constituting the pair or the opposite direction. In the second detection circuit 20, the second direction D2 is an intermediate direction of the magnetization direction of the magnetization fixed layer in the two MR elements constituting the pair or a direction opposite thereto.

  FIG. 3 shows an example in which a plurality of MR elements constituting an MR element array include only one MR element pair as follows. The magnetic detection element R11 includes a pair of MR elements R111 and R112. The magnetic detection element R12 includes a pair of MR elements R121 and R122. The magnetic detection element R13 includes a pair of MR elements R131 and R132. The magnetic detection element R14 includes a pair of MR elements R141 and R142. The magnetic detection element R21 includes a pair of MR elements R211 and R212. The magnetic detection element R22 includes a pair of MR elements R221 and R222. The magnetic detection element R23 includes a pair of MR elements R231 and R232. The magnetic detection element R24 includes a pair of MR elements R241 and R242. In FIG. 3, a solid arrow indicates the magnetization direction of the magnetization fixed layer in the MR element, and a white arrow indicates the magnetization direction of the free layer in the MR element.

  Here, with reference to FIG. 5, the relationship of the magnetization direction of the magnetization fixed layer in the two MR elements constituting the pair will be described. In FIG. 5, arrows with reference signs D111 and D112 represent the magnetization directions of the magnetization fixed layers of the MR elements R111 and R112, respectively. The magnetization directions D111 and D112 of the magnetization fixed layers of the MR elements R111 and R112 are fixed so that the intermediate direction thereof is the same direction (X direction) as the first direction D1. The magnetization direction D111 of the magnetization fixed layer of the MR element R111 is a direction rotated by an angle φ clockwise from the first direction D1. The magnetization direction D112 of the magnetization fixed layer of the MR element R112 is a direction rotated by an angle φ counterclockwise from the first direction D1. Hereinafter, the angle φ is referred to as an offset angle φ.

  The magnetization directions of the magnetization fixed layers of the MR elements R121 and R122 are fixed so that the intermediate direction thereof is the opposite direction (−X direction) to the first direction D1. The magnetization directions of the magnetization fixed layers of the MR elements R131 and R132 are also fixed so that the intermediate direction thereof is opposite to the first direction D1. The magnetization direction of the magnetization fixed layer of the MR element R131 is the same as the magnetization direction of the magnetization fixed layer of the MR element R121. The magnetization direction of the magnetization fixed layer of the MR element R132 is the same as the magnetization direction of the magnetization fixed layer of the MR element R122. The magnetization direction of the magnetization fixed layer of the MR elements R121 and R131 is opposite to the magnetization direction D111 of the magnetization fixed layer of the MR element R111 shown in FIG. The magnetization direction of the magnetization fixed layer of the MR elements R122 and R132 is opposite to the magnetization direction D112 of the magnetization fixed layer of the MR element R112 shown in FIG.

  The magnetization directions of the magnetization fixed layers of the MR elements R141 and R142 are fixed so that the intermediate direction thereof is the same direction (X direction) as the first direction D1. The magnetization direction of the magnetization fixed layer of the MR element R141 is the same as the magnetization direction D111 of the magnetization fixed layer of the MR element R111 shown in FIG. The magnetization direction of the magnetization fixed layer of the MR element R142 is the same as the magnetization direction D112 of the magnetization fixed layer of the MR element R112 shown in FIG.

  In FIG. 5, arrows with symbols D211 and D212 indicate the magnetization directions of the magnetization fixed layers of the MR elements R211 and R212, respectively. The magnetization directions D211 and D212 of the magnetization fixed layers of the MR elements R211 and R212 are fixed so that the intermediate direction thereof is the same direction (Y direction) as the second direction D2. The magnetization direction D211 of the magnetization fixed layer of the MR element R211 is a direction rotated by the offset angle φ clockwise from the second direction D2. The magnetization direction D212 of the magnetization fixed layer of the MR element R212 is a direction rotated by the offset angle φ counterclockwise from the second direction D2.

  The magnetization directions of the magnetization fixed layers of the MR elements R221 and R222 are fixed so that the intermediate direction is the opposite direction (−Y direction) to the second direction D2. The magnetization directions of the magnetization fixed layers of the MR elements R231 and R232 are also fixed so that the intermediate direction thereof is opposite to the second direction D2. The magnetization direction of the magnetization fixed layer of the MR element R231 is the same as the magnetization direction of the magnetization fixed layer of the MR element R221. The magnetization direction of the magnetization fixed layer of the MR element R232 is the same as the magnetization direction of the magnetization fixed layer of the MR element R222. The magnetization direction of the magnetization fixed layer of the MR elements R221 and R231 is opposite to the magnetization direction D211 of the magnetization fixed layer of the MR element R211 shown in FIG. The magnetization direction of the magnetization fixed layer of the MR elements R222 and R232 is opposite to the magnetization direction D212 of the magnetization fixed layer of the MR element R212 shown in FIG.

  The magnetization directions of the magnetization fixed layers of the MR elements R241 and R242 are fixed so that the intermediate direction thereof is the same direction (Y direction) as the second direction D2. The magnetization direction of the magnetization fixed layer of the MR element R241 is the same as the magnetization direction D211 of the magnetization fixed layer of the MR element R211 shown in FIG. The magnetization direction of the magnetization fixed layer of the MR element R242 is the same as the magnetization direction D212 of the magnetization fixed layer of the MR element R212 shown in FIG.

  Note that the magnetization direction of the magnetization fixed layer in the plurality of MR elements in the detection circuits 10 and 20 may be slightly deviated from the above-mentioned direction from the viewpoint of the accuracy of manufacturing the MR elements.

  In the first detection circuit 10, the potential difference between the output ports E11 and E12 changes according to the angle formed by the direction DM of the detected magnetic field MF with respect to the first direction D1 (X direction). Accordingly, the first detection circuit 10 generates the first signal S1 having a correspondence relationship with the angle formed by the direction DM of the detected magnetic field MF with respect to the first direction D1 (X direction).

  In the second detection circuit 20, the potential difference between the output ports E21 and E22 changes according to the angle formed by the direction DM of the detected magnetic field MF with respect to the second direction D2 (Y direction). Accordingly, the second detection circuit 20 generates the second signal S2 having a correspondence relationship with the angle formed by the direction DM of the detected magnetic field MF with respect to the second direction D2 (Y direction).

  Next, an example of the configuration of the bridge circuit and the magnetic detection element will be described with reference to FIGS. FIG. 6 is a plan view showing the bridge circuit 14 shown in FIG. FIG. 7 is a perspective view showing a part of one magnetic detection element in FIG. In the example shown in FIG. 6, each of the magnetic detection elements R11, R12, R13, and R14 of the bridge circuit 14 is configured by an MR element array including eight MR elements 50 connected in series. The plurality of MR elements 50 constituting the MR element array includes four pairs of MR elements 50. The MR element array includes a plurality of lower electrodes 41 and a plurality of upper electrodes 42 that connect eight MR elements 50 in series. The MR element 50 has a lower end surface and an upper end surface. The configuration of the bridge circuit 24 is the same as that of the bridge circuit 14 shown in FIG.

  The plurality of lower electrodes 41 are disposed on a substrate (not shown). Each lower electrode 41 has an elongated shape. A gap is formed between two adjacent lower electrodes 41. As shown in FIG. 7, on the upper surface of the lower electrode 41, two adjacent MR elements 50 are arranged in the vicinity of both ends in the longitudinal direction. Each upper electrode 42 has an elongated shape, and is disposed on two adjacent lower electrodes 41 to electrically connect two adjacent MR elements 50.

  As shown in FIG. 7, the MR element 50 includes an antiferromagnetic layer 54, a magnetization fixed layer 53, a nonmagnetic layer 52, and a free layer 51 that are sequentially stacked from the lower electrode 41 side. The antiferromagnetic layer 54 is made of an antiferromagnetic material and causes exchange coupling with the magnetization fixed layer 53 to fix the magnetization direction of the magnetization fixed layer 53. The arrangement of the layers 51 to 54 in the MR element 50 may be upside down from the arrangement shown in FIG.

  The free layer 51 has a first surface in contact with the nonmagnetic layer and a second surface opposite to the first surface. In the example shown in FIG. 7, the second surface of the free layer 51 constitutes the upper end surface of the MR element 50. In FIG. 2, reference numeral 11 represents the shape of the second surface of the free layer 51 in the MR element 50 in the first detection circuit 10, and reference numeral 21 represents the free element in the MR element 50 in the second detection circuit 20. The shape of the 2nd surface of the layer 51 is represented.

  The bridge circuit 14 illustrated in FIG. 6 includes four connection electrodes 431, 432, 433, and 434 that electrically connect two magnetic detection elements. The connection electrodes 431 to 434 are arranged on a substrate (not shown).

  The connection electrode 431 electrically connects the MR element 50 located at one end of the magnetic detection element R11 and the MR element 50 located at one end of the magnetic detection element R13, and is electrically connected to the power supply port V1. ing. The connection electrode 432 electrically connects the MR element 50 located at the other end of the magnetic detection element R11 and the MR element 50 located at one end of the magnetic detection element R12, and is electrically connected to the output port E11. Has been. The connection electrode 433 electrically connects the MR element 50 located at the other end of the magnetic detection element R13 and the MR element 50 located at one end of the magnetic detection element R14, and is electrically connected to the output port E12. Has been. The connection electrode 434 electrically connects the MR element 50 located at the other end of the magnetic detection element R12 and the MR element 50 located at the other end of the magnetic detection element R14, and is electrically connected to the ground port G1. It is connected.

  In the magnetic detection element R11, for example, the magnetization direction of the magnetization fixed layer of the first to fourth MR elements 50 from the power supply port V1 side is the same as the magnetization direction of the magnetization fixed layer of the MR element R111 shown in FIG. The magnetization directions of the magnetization fixed layers of the fifth to eighth MR elements 50 from the power supply port V1 side are the same as the magnetization directions of the magnetization fixed layers of the MR element R112 shown in FIG. In this case, the first and fifth MR elements 50, the second and sixth MR elements 50, the third and seventh MR elements 50, the fourth and eighth MR elements 50 constitute a pair, respectively. Yes.

  In the magnetic detection element R12, for example, the magnetization direction of the magnetization fixed layer of the first to fourth MR elements 50 from the output port E11 side is the same as the magnetization direction of the magnetization fixed layer of the MR element R121 shown in FIG. The magnetization directions of the magnetization fixed layers of the fifth to eighth MR elements 50 from the output port E11 side are the same as the magnetization directions of the magnetization fixed layers of the MR element R122 shown in FIG. In this case, the first and fifth MR elements 50, the second and sixth MR elements 50, the third and seventh MR elements 50, the fourth and eighth MR elements 50 constitute a pair, respectively. Yes.

  In the magnetic detection element R13, for example, the magnetization direction of the magnetization fixed layer of the first to fourth MR elements 50 from the power supply port V1 side is the same as the magnetization direction of the magnetization fixed layer of the MR element R131 shown in FIG. The magnetization directions of the magnetization fixed layers of the fifth to eighth MR elements 50 from the power supply port V1 side are the same as the magnetization directions of the magnetization fixed layers of the MR element R132 shown in FIG. In this case, the first and fifth MR elements 50, the second and sixth MR elements 50, the third and seventh MR elements 50, the fourth and eighth MR elements 50 constitute a pair, respectively. Yes.

  In the magnetic detection element R14, for example, the magnetization direction of the magnetization fixed layer of the first to fourth MR elements 50 from the output port E12 side is the same as the magnetization direction of the magnetization fixed layer of the MR element R141 shown in FIG. The magnetization directions of the magnetization fixed layers of the fifth to eighth MR elements 50 from the output port E12 side are the same as the magnetization directions of the magnetization fixed layers of the MR element R142 shown in FIG. In this case, the first and fifth MR elements 50, the second and sixth MR elements 50, the third and seventh MR elements 50, the fourth and eighth MR elements 50 constitute a pair, respectively. Yes.

  Next, a method for calculating the angle detection value θs in the angle detection value calculation unit 31 will be described with reference to FIGS. 3 and 4. In the example shown in FIG. 3, ideally, the waveform of the first signal S1 is a cosine waveform dependent on the angle θ, and the waveform of the second signal S2 is a sine dependent on the angle θ. (Sine) Waveform. In this case, the phase of the second signal S2 differs from the phase of the first signal S1 by ¼ of the signal period T, that is, π / 2 (90 °).

  When the angle θ is greater than or equal to 0 ° and less than 90 °, and greater than 270 ° and less than or equal to 360 °, the first signal S1 is a positive value, and the angle θ is greater than 90 ° and smaller than 270 ° The first signal S1 has a negative value. When the angle θ is larger than 0 ° and smaller than 180 °, the second signal S2 is a positive value. When the angle θ is larger than 180 ° and smaller than 360 °, the second signal S2 is positive. S2 is a negative value.

  The detected angle value calculation unit 31 calculates an detected angle value θs having a corresponding relationship with the angle θ based on the first and second signals S1 and S2. Specifically, for example, the angle detection value calculation unit 31 calculates θs by the following equation (1). “Atan” represents an arc tangent.

  θs = atan (S2 / S1) (1)

  Atan (S2 / S1) in Equation (1) represents arctangent calculation for obtaining θs. In the range where θs is 0 ° or more and less than 360 °, the solution of θs in Equation (1) has two values that differ by 180 °. However, it is possible to determine which of the two solutions of θs in Equation (1) is the true value of θs by the positive / negative combination of S1 and S2. That is, when S1 is a positive value, θs is in the range of 0 ° to less than 90 ° and greater than 270 ° to 360 °. When S1 is a negative value, θs is greater than 90 ° and smaller than 270 °. When S2 is a positive value, θs is larger than 0 ° and smaller than 180 °. When S2 is a negative value, θs is greater than 180 ° and smaller than 360 °. The detected angle calculation unit 31 calculates θs within a range of 0 ° or more and less than 360 ° based on the determination of the expression (1) and the positive / negative combination of S1 and S2.

  As described above, when the direction DM of the detected magnetic field MF rotates with the predetermined period, the first and second signals S1 and S2 change periodically with a signal period T equal to the predetermined period. To do. Each of the signals S1 and S2 is ideally a sine curve (including a sine waveform and a cosine waveform). However, actually, for example, the magnetization direction of the magnetization fixed layer 53 of the MR element 50 varies due to the influence of the detected magnetic field MF or the like, or the magnetization direction of the free layer 51 of the MR element 50 differs from the shape of the free layer 51. The waveform of each of the signals S1 and S2 is distorted from the sine curve due to the fact that it does not coincide with the direction DM of the detected magnetic field MF due to the influence of the directivity or the like.

  The fact that each of the waveforms of the signals S1 and S2 is distorted from the sine curve means that each of the signals S1 and S2 has an ideal component that periodically changes to draw an ideal sine curve and one or more of the ideal components. And one or more error components corresponding to the higher harmonics. Since each of the signals S1 and S2 includes one or more error components, the detected angle value θs includes an error. Hereinafter, an error in the detected angle value θs is referred to as an angle error. When the direction DM of the detected magnetic field MF rotates at the predetermined period, the angle error may include one or more angular error components that periodically change at one or more periods different from the predetermined period.

  In the course of research by the inventors of the present application, it has been found that, in general, in a magnetic sensor, the angle error changes according to the strength of the detected magnetic field, that is, the angle error depends on the magnetic field strength. In addition, in the course of research by the inventors of the present application, the dependence of the angle error on the magnetic field strength is mainly an angle that changes at a quarter of the predetermined period among the one or more angle error components described above. It was found that it was caused by an error component (hereinafter referred to as an angular error quaternary component). That is, the manner in which the angular error quaternary component changes with respect to the change in the intensity of the detected magnetic field MF (hereinafter referred to as applied magnetic field strength) in the magnetic field detection unit 3 is the way in which the overall angle error changes with respect to the change in applied magnetic field strength. It was the same. It has also been found that the overall angle error can be reduced by reducing the angular error quaternary component.

  Here, consider a case where the variation amount of the angle error becomes large within a predetermined range assumed as the range of the applied magnetic field strength when the magnetic sensor 1 is used due to the dependence of the angle error on the magnetic field strength. In this case, if the applied magnetic field strength is different from the specific value even if the detection angle is corrected so that the angle error is reduced when the applied magnetic field strength is a specific value within the predetermined range, It can happen that the error is not reduced sufficiently.

  The maximum value of the absolute value of the angular error quaternary component when the direction DM of the detected magnetic field MF rotates in the predetermined cycle is represented by the symbol E4. If the variation amount of the maximum value E4 of the absolute value of the angular error quaternary component is reduced in a wide range of the applied magnetic field strength, the variation amount of the angle error can be reduced in a wide range of the applied magnetic field strength. By doing so, even if the angle error is large, it is possible to reduce the angle error in a wide range of the applied magnetic field strength by performing a correction process that does not vary depending on the applied magnetic field strength.

  In the magnetic sensor 1 according to the present embodiment, the applied magnetic field strength is a subrange that is a part of the range of 20 to 150 mT, and the difference between the upper limit and the lower limit is changed within the subrange that is 30 mT or more. The variation amount of the maximum value E4 of the absolute value of the angular error quaternary component is 0.1 ° or less. It can be said that the width of the subrange where the difference between the upper limit and the lower limit is 30 mT or more is sufficiently wide for practical use of the magnetic sensor 1 as the range of the applied magnetic field strength when the magnetic sensor 1 is used. According to the magnetic sensor 1 according to the present embodiment having such characteristics, it is possible to reduce the variation amount of the angle error in a wide range of the applied magnetic field intensity.

  Hereinafter, a method for realizing the above characteristics of the magnetic sensor 1 will be described in detail. Research by the inventors of the present application has found that the angular error quaternary component depends on two error components included in each of the signals S1 and S2. First, this will be described. When the direction DM of the detected magnetic field MF rotates at the predetermined period, the first signal S1 includes a first ideal component V11 that periodically changes to draw an ideal sine curve, and a first ideal. The first third harmonic component V13, which is an error component corresponding to the third harmonic with respect to the component V11, and the first fifth harmonic, which is an error component corresponding to the fifth harmonic with respect to the first ideal component V11. The second signal S2 includes the component V15, and the second signal S2 is an error corresponding to a third ideal harmonic with respect to the second ideal component V21 that periodically changes to draw an ideal sine curve and the second ideal component V21. It includes a second third harmonic component V23, which is a component, and a second fifth harmonic component V25, which is an error component corresponding to the fifth harmonic relative to the second ideal component V21.

  Here, the ratio of the first third harmonic component V13 to the first ideal component V11 when the first ideal component V11 takes the maximum value is defined as a first ratio V13r, and the first ideal component V11 The ratio of the first fifth harmonic component V15 with respect to the first ideal component V11 when A takes the maximum value is defined as a second ratio V15r, and the second when the second ideal component V21 takes the maximum value The ratio of the second third harmonic component V23 to the ideal component V21 is defined as the third ratio V23r, and the second second component V21 relative to the second ideal component V21 when the second ideal component V21 takes the maximum value is defined. The ratio of the fifth harmonic component V25 is defined as a fourth ratio V25r. The average value of the first ratio V13r and the third ratio V23r is defined as the third harmonic component ratio and is represented by the symbol V3r. The average value of the second ratio V15r and the fourth ratio V25r is defined as the fifth harmonic component ratio and is represented by the symbol V5r.

  According to the research by the inventors of the present application, it has been found that the maximum absolute value E4 of the angular error quaternary component is proportional to the absolute value of the difference between the third harmonic component ratio V3r and the fifth harmonic component ratio V5r. E4 is approximately represented by the following equation (2). In the formula (2), the unit of E4 is degree, and the unit of V3r and V5r is%.

  E4 = | V3r−V5r | × 0.56 (2)

  From equation (2), in principle, E4 becomes zero when V3r and V5r are equal. Further, from the formula (2), E4 becomes 0.1 ° when the absolute value of the difference between V3r and V5r is 0.18%, and E4 when the absolute value of the difference between V3r and V5r is 0.09%. Becomes 0.05 °.

  Hereinafter, the amount of change in the absolute value of the difference between V3r and V5r when the applied magnetic field strength changes within the subrange is also referred to as the amount of change in the absolute value of the difference between V3r and V5r within the subrange. Further, the variation amount of E4 when the applied magnetic field intensity changes within the sub-range is also referred to as the variation amount of E4 within the sub-range. From equation (2), if the fluctuation amount of the absolute value of the difference between V3r and V5r within the subrange is 0.18% or less, the fluctuation amount of E4 within the subrange is 0.1 ° or less. Further, if the variation amount of the absolute value of the difference between V3r and V5r within the sub-range is 0.09% or less, the variation amount of E4 within the sub-range is 0.05 ° or less.

  Here, with reference to FIGS. 8 to 11, first to fourth examples of the relationship between a plurality of error components obtained by simulation and an angular error quaternary component will be described.

  8 to 11, (a) shows the waveforms of V11, V13r, and V15r, (b) shows the waveforms of V21, V23r, and V25r, and (c) shows the waveform of the angular error quaternary component. ing. In any of (a), (b), and (c), the horizontal axis indicates the angle θ. The vertical axis | shaft in (a) has shown each value of V11, V13r, V15r. V11 represents the maximum value as 100%. The vertical axis | shaft in (b) has shown each value of V21, V23r, V25r. V21 represents the maximum value as 100%. The vertical axis in (c) indicates the value of the angular error quaternary component (the unit is degrees).

  In the first example shown in FIG. 8, V13r, V15r, V23r, and V25r are all 0.1%. In this case, both V3r and V5r are 0.1%. In this case, since V3r and V5r are equal, the angular error quaternary component is zero regardless of the angle θ, and E4 is zero.

  In the second example shown in FIG. 9, both V13r and V23r are zero, and both V15r and V25r are 0.1%. In this case, V3r is zero and V5r is 0.1%. In this case, the absolute value of the difference between V3r and V5r is 0.1%, and E4 is 0.056 °.

  In the third example shown in FIG. 10, V13r and V23r are both 0.1%, and V15r and V25r are both zero. In this case, V3r is 0.1% and V5r is zero. In this case, the absolute value of the difference between V3r and V5r is 0.1%, and E4 is 0.056 °.

  In the fourth example shown in FIG. 11, V13r and V23r are both -0.1%, and V15r and V25r are both 0.1%. In this case, V3r is -0.1% and V5r is 0.1%. In this case, the absolute value of the difference between V3r and V5r is 0.2%, and E4 is 0.11 °.

  Next, with reference to FIG. 12, the result of the simulation which calculated | required the relationship between the absolute value of the difference of V3r and V5r represented by Formula (2), and E4 is demonstrated. In this simulation, the relationship between the absolute value of the difference between V3r and V5r and E4 was determined for various combinations of the values of V3r and V5r. The result is shown in FIG. In FIG. 12, the horizontal axis indicates the absolute value of the difference between V3r and V5r, and the vertical axis indicates E4. In FIG. 12, a plurality of square points represent combinations of the absolute value of the difference between V3r and V5r and the value of E4 obtained by simulation, respectively, and the straight line represents the relationship between the absolute value of the difference between V3r and V5r and E4. Is an approximate straight line. Equation (2) represents this approximate straight line.

  Hereinafter, changes in V3r, V5r, and E4 when the applied magnetic field strength is changed are referred to as magnetic field strength dependence of V3r, V5r, and E4, respectively. As described above, E4 is proportional to the absolute value of the difference between V3r and V5r. From this, it can be seen that in order to reduce the fluctuation amount of E4 within the desired sub-range, it is only necessary to reduce the fluctuation amount of the absolute value of the difference between V3r and V5r in each applied magnetic field strength within that sub-range. . This is because by controlling the magnetic field strength dependence of V3r and V5r so that the rate of change in V3r with respect to the increase in applied magnetic field strength and the rate of change in V5r with respect to the increase in applied magnetic field strength are close to each other within the sub-range. Can be realized.

  In the present embodiment, by using the first means and the second means described below, the ratio of the change in V3r with respect to the increase in the applied magnetic field strength and the change in V5r with respect to the increase in the applied magnetic field strength in the desired subrange. The magnetic field strength dependency of V3r and the magnetic field strength dependency of V5r are controlled so that the ratios are close to each other. The first means is to control the shape of the MR element 50, particularly the shape of the free layer 51. The second means is to adjust the offset angle φ described with reference to FIG.

  First, the first means will be described. First, a method for controlling the shape of the free layer 51 in the present embodiment will be described with reference to FIGS. In the present embodiment, the shape of the free layer 51 is defined by the shape of the second surface of the free layer 51. The MR element 50 is produced, for example, by forming a laminated body of a plurality of films to be a plurality of layers constituting the MR element 50 and then etching the laminated body using an etching mask having a desired shape. The shape of the second surface of the free layer 51 is defined by the shape of the etching mask. The shapes of the first surface of the free layer 51 and the upper and lower surfaces of the plurality of layers other than the free layer 51 constituting the MR element 50 are the same as or similar to the shape of the second surface of the free layer 51. It is a shape.

  FIG. 13 is an explanatory diagram for explaining the shape of the second surface of the free layer 51. In FIG. 13, reference numeral 51 a indicates the outer edge of the second surface of the free layer 51. In FIG. 13, the shape of the outer edge 51a of the second surface is exaggerated for easy understanding. Reference numeral 51C indicates a reference circle used to define the shape of the second surface of the free layer 51. The reference circle 51C is a perfect circle.

  Here, the center of gravity of the second surface of the free layer 51 is defined as the center of the second surface. Further, an angle formed by a straight line connecting an arbitrary point on the outer edge 51a of the second surface and the center of the second surface with respect to the X direction (see FIG. 2) is represented by the symbol θa. The angle θa is represented by a value when viewed in the counterclockwise direction from the X direction. The range of the angle θa is 0 ° or more and less than 360 °. Further, the distance from the center of the second surface to an arbitrary point on the outer edge 51a of the second surface is defined as R (θa).

  In the present embodiment, the shape of the second surface is controlled as follows at the stage of manufacturing the MR element 50. In other words, in the present embodiment, the shape of the second surface is changed to a four-fold rotationally symmetric shape that is not five or more rotationally symmetric, and the distortion ratio and the distortion direction described later are controlled. A four-fold rotationally symmetric shape that is not five or more rotationally symmetric does not include a shape that is 4 × n rotationally symmetric when n is an integer of two or more. Hereinafter, a four-fold rotationally symmetric shape that is not five or more times rotationally symmetric is referred to as a four-fold symmetric shape.

  When the shape of the second surface is a 4-fold symmetrical shape, when the angle θa is changed within the range of 0 ° or more and less than 360 °, R (θa) has four values different from each other by 90 °. In this case, the maximum value is taken, and the angle θa is changed to take the minimum value when the other four values differ by 90 °.

  Here, the reference circle 51C is defined with the average value of the maximum value of R (θa) and the minimum value of R (θa) as the radius Rc of the reference circle 51C. The center of the reference circle 51C coincides with the center of the second surface. Further, a value obtained by subtracting the radius Rc of the reference circle 51C from the maximum value of R (θa) is defined as a distortion length d. Further, the ratio of the strain length d to Rc expressed as a percentage is defined as a strain ratio dr, and the ratio of R (θa) to Rc expressed as a percentage is defined as r (θa). Further, the angle θa when R (θa) takes the maximum value within the range where the angle θa is 0 ° or more and less than 90 ° is defined as the strain direction α. In the present embodiment, r (θa) is expressed by the following equation (3), for example.

  r (θa) = 100 + dr · cos (4 (θa−α)) (3)

  FIG. 14 shows an example of the relationship between the angles θa and r (θa). In this example, the strain ratio dr is 1%, and the strain direction α is 0 °.

  FIG. 15 shows a case where the angle θa and r (θa) have the relationship shown in FIG. 14 and a part of the reference circle 51C and the outer edge 51a of the second surface when the angle θa is in the range of 0 ° to 90 °. Is shown. In FIG. 15, the horizontal axis indicates the position in the X direction, and the vertical axis indicates the position in the Y direction. The position in the X direction and the position in the Y direction are expressed as relative values when the center of the reference circle 51C is the origin and the radius Rc of the reference circle 51C is 100.

  In the present embodiment, the adjustment range of the strain ratio dr is preferably 0 to 10%. If the shape of the outer edge 51a of the second surface is a square, the strain ratio dr exceeds 10%. In the present embodiment, the shape of the outer edge 51a of the second surface does not include a square. Note that the shape of the outer edge 51a of the second surface when the strain ratio dr is about 1% is not greatly distorted from the perfect circle as shown in FIG. 13, but is a perfect circle as shown in FIG. It will be close to.

  Next, with reference to the result of the first experiment, it will be described that the magnetic field dependency of each of V3r, V5r, and E4 can be changed by changing the shape of the second surface of the free layer 51. In the first experiment, the offset angle φ is set to 0 °, and the shape of the second surface of the free layer 51 is changed to the first to third shapes to change the magnetic field strengths of V3r, V5r, and E4. Dependency was examined. FIG. 16 is a characteristic diagram showing changes in the magnetic field strength dependency of V3r and V5r when the shape of the second surface of the free layer 51 is changed. FIG. 17 is a characteristic diagram showing a change in the magnetic field strength dependence of E4 when the shape of the second surface of the free layer 51 is changed.

  The shape of the second surface of the free layer 51 is defined by the strain ratio dr and the strain direction α. The first shape of the second surface is a shape in which dr is 0.5% and α is 45 °. The second shape of the second surface is a shape where dr is zero. The third shape of the second surface is a shape where dr is 0.5% and α is 0 °. In FIG. 16, V3r and V5r corresponding to the first shape are expressed as V3r (dr = 0.5%, α = 45 °), V5r (dr = 0.5%, α = 45 °), and the second V3r and V5r corresponding to the shape of V3r are expressed as V3r (dr = 0) and V5r (dr = 0), and V3r and V5r corresponding to the third shape are V3r (dr = 0.5%, α = 0 °). ), V5r (dr = 0.5%, α = 0 °). In FIG. 17, E4 corresponding to the first shape is expressed as E4 (dr = 0.5%, α = 45 °), and E4 corresponding to the second shape is expressed as E4 (dr = 0). E4 corresponding to the third shape is represented as E4 (dr = 0.5%, α = 0 °).

  16 and 17 are examples shown for explaining the tendency of the change in the magnetic field strength dependency of V3r, V5r, and E4 when at least one of the strain ratio dr and the strain direction α is changed. . Although not shown in FIGS. 16 and 17, when dx is changed while α is constant, changes in the magnetic field strength dependence of V3r, V5r, and E4 tend to be described more significantly as dx increases. , Dx decreases, the magnetic field strength dependence of V3r, V5r, E4 approaches the magnetic field strength dependence of V3r, V5r, E4 when dr is zero, respectively.

  From FIG. 16, the following can be seen as the tendency of the change in the magnetic field strength dependence of V3r and V5r. First, when the strain ratio dr is set to a value larger than zero, the magnetic field strength dependency of V3r and the magnetic field strength dependency of V5r are changed as compared with the case where the strain ratio dr is zero. Further, the magnetic field strength dependency of V3r and the magnetic field strength dependency of V5r also change depending on the strain direction α. Further, the method of changing the magnetic field strength dependency of V3r and the method of changing the magnetic field strength dependency of V5r when at least one of the strain ratio dr and the strain direction α is changed are different from each other. In the example shown in FIG. 16, when dr is 0.5% and α is 0 °, the magnetic field strength dependence of V3r changes so that V3r increases as compared with the case where dr is zero. On the other hand, the magnetic field strength dependence of V5r changes so that V5r decreases. In addition, when dr is 0.5% and α is 45 ° as compared to when dr is zero, the dependence of V3r on the magnetic field strength changes so that V3r decreases, whereas the magnetic field strength of V5r. The dependence changes as V5r increases.

  The change amount of V3r when at least one of the strain ratio dr and the strain direction α is changed, and the change amount of V5r when at least one of the strain ratio dr and the strain direction α is changed are both applied magnetic field strength. It depends on.

  As described above, the change in the magnetic field strength dependency of V3r and the change in the magnetic field strength dependency of V5r when changing at least one of the strain ratio dr and the strain direction α are different from each other in FIG. As shown, the dependence of E4 on the magnetic field strength can be changed by changing at least one of the strain ratio dr and the strain direction α.

  Next, the second means will be described with reference to the result of the second experiment. In the second experiment, the shape of the second surface of the free layer 51 is changed to a shape in which dr is zero, and the offset angle φ is changed to three ways of 0 °, 8 °, and 17 °, and V3r, V5r, and E4. The magnetic field strength dependence of each of was investigated. FIG. 18 is a characteristic diagram showing changes in the magnetic field strength dependence of V3r and V5r when the offset angle φ is changed. FIG. 19 is a characteristic diagram showing a change in the magnetic field strength dependence of E4 when the offset angle φ is changed.

  In FIG. 18, V3r and V5r when the offset angle φ is 0 ° are expressed as V3r (φ = 0 °) and V5r (φ = 0 °), and V3r and V5r when the offset angle φ is 8 °. Are expressed as V3r (φ = 8 °) and V5r (φ = 8 °), and V3r and V5r are V3r (φ = 17 °) and V5r (φ = 17 °) when the offset angle φ is 17 °. It is written. In FIG. 18, three lines corresponding to V5r (φ = 0 °), V5r (φ = 8 °), and V5r (φ = 17 °) are overlapped. In FIG. 19, E4 when the offset angle φ is 0 ° is expressed as E4 (φ = 0 °), and E4 when the offset angle φ is 8 ° is expressed as E4 (φ = 8 °). E4 when the offset angle φ is 17 ° is expressed as E4 (φ = 17 °).

  As can be seen from FIG. 18, when the offset angle φ is changed, the magnetic field strength dependency of V5r changes little or hardly, whereas the magnetic field strength dependency of V3r changes. Accordingly, as shown in FIG. 19, when the offset angle φ is changed, the magnetic field strength dependency of E4 changes.

  As can be seen from FIGS. 17 and 19, the magnetic field strength dependence of E4 can be changed by using the first means and the second means independently. However, when the first means and the second means are each used alone, it is difficult to sufficiently reduce the variation amount of E4 in a wide range of the applied magnetic field strength. Therefore, when each of the first means and the second means is used alone, the characteristics of the magnetic sensor 1 according to the present embodiment, that is, the applied magnetic field strength is part of the range of 20 to 150 mT. It may be difficult to realize the characteristic that the variation amount of E4 is 0.1 ° or less when the subrange changes within the subrange in which the difference between the upper limit and the lower limit is 30 mT or more.

  On the other hand, when the first means and the second means are used in combination, the variation amount of E4 in a wider range of the applied magnetic field strength compared to the case where the first means and the second means are each used alone. Can be made sufficiently small, and as a result, the characteristics of the magnetic sensor 1 according to the present embodiment can be easily realized.

  Hereinafter, first to third examples of the magnetic sensor 1 according to the present embodiment and a magnetic sensor of a comparative example will be described. Each of the first to third embodiments is an example in which the first means and the second means are used in combination. The magnetic sensor of the comparative example is an example in which the shape of the second surface of the free layer 51 is a shape where dr is zero and the offset angle φ is 0 °.

[First embodiment]
In the magnetic sensor 1 of the first embodiment, the shape of the second surface of the free layer 51 is such that dr is 1%, α is 0 °, and the offset angle φ is 25 °. FIG. 20 is a characteristic diagram showing the magnetic field strength dependency of V3r and V5r in the magnetic sensor 1 of the first embodiment and the magnetic sensor of the comparative example. FIG. 21 is a characteristic diagram showing the magnetic field strength dependence of E4 in the magnetic sensor 1 of the first embodiment and the magnetic sensor of the comparative example. In FIG. 20, V3r and V5r in the magnetic sensor 1 of the first embodiment are expressed as V3r (dr = 1%, φ = 25 °) and V5r (dr = 1%, φ = 25 °), respectively. V3r and V5r in the magnetic sensor are expressed as V3r (dr = 0, φ = 0 °) and V5r (dr = 0, φ = 0 °). In FIG. 21, E4 in the magnetic sensor 1 of the first embodiment is expressed as E4 (dr = 1%, φ = 25 °), and E4 in the magnetic sensor of the comparative example is E4 (dr = 0, φ = 0 °).

  As shown in FIGS. 20 and 21, in the magnetic sensor 1 of the first embodiment, the variation amount of the absolute value of the difference between V3r and V5r is 0.18% or less in the range of applied magnetic field strength of 40 to 150 mT. And the variation amount of E4 is 0.1 ° or less. Further, in the magnetic sensor 1 of the first embodiment, in the range of the applied magnetic field strength of 50 to 120 mT, the variation amount of the absolute value of the difference between V3r and V5r is 0.09% or less, and the variation amount of E4 is 0. .05 ° or less. The magnetic sensor 1 of the first example satisfies the characteristic requirements of the magnetic sensor 1 according to the present embodiment. On the other hand, the magnetic sensor of the comparative example does not satisfy the requirements for the characteristics of the magnetic sensor 1 according to the present embodiment.

  Here, a first example and a second example of correction processing in the correction processing unit 32 of the calculation unit 30 shown in FIG. 4 will be described.

  In the first example of the correction process, the following test is performed before the magnetic sensor 1 is shipped, and correction information to be stored in the correction information holding unit 33 is created. In the test, the applied magnetic field strength is set to a specific value within the subrange. Then, the angle θ formed by the direction DM of the detected magnetic field MF with respect to the reference direction DR is changed at equal intervals within the range of 0 ° to 360 °, and the angle detection value calculation unit 31 performs a plurality of angles θ. The calculated angle detection value θs is obtained, and an angle error that is an error of the angle detection value θs is obtained. Hereinafter, the angle error is represented by the symbol AE.

  The angle error AE changes at a cycle that is 1/4 of the cycle of the angle θ. The main component of the angle error AE is an angular error quaternary component. Here, m is the number of the plurality of angles θ for obtaining the detected angle value θs. In order to create correction information, m needs to be an integer of 8 or more from the sampling theorem. It is preferable that 0 ° is included in the plurality of angles θ for obtaining the angle detection value θs, and in this case, m is an integer of 16 or more.

  Here, the angle θ when the detected angle value θs is obtained is represented as θn. n is an integer of 1 to m. Further, the detected angle value θs corresponding to θn is expressed as θsn, and the angle error AE corresponding to θn is expressed as AEn. A combination of θsn and AEn is represented as (θsn, AEn). In the test, (θsn, AEn) is stored in the correction information holding unit 33 as correction information.

  When the magnetic sensor 1 is used, the correction processing unit 32 obtains the corrected angle detection value θt for the input angle detection value θs using linear interpolation based on the correction information (θsn, AEn). More specifically, the correction processing unit 32 uses the linear interpolation to input the input angle based on two correction information (θsn, AEn) corresponding to θsn before and after the input angle detection value θs. An approximate angle error AEs corresponding to the detected value θs is obtained, and a value obtained by subtracting AEs from θs is set as a corrected angle detected value θt. The approximate angle error AEs is an angle error AEn corresponding to a specific θsn when the input angle detection value θs matches a specific θsn, and by linear interpolation when the input angle detection value θs is other than θsn. This is the estimated angular error.

  Hereinafter, the first example of the correction process will be described more specifically with reference to the first example. Here, the range of 50 to 120 mT of the applied magnetic field strength is set as the sub-range. FIG. 22 shows the relationship between the angle θ and the angle error AE of the detected angle value θs when the applied magnetic field strength is 20 mT, 80 mT, and 150 mT, respectively, in the first embodiment. In FIG. 22, the horizontal axis represents the angle θ, and the vertical axis represents the angle error AE. In FIG. 22, the angle error AE when the applied magnetic field intensity is 20 mT, 80 mT, and 150 mT is expressed as AE (20 mT), AE (80 mT), and AE (150 mT). The relationship between the angle θ and the angle error AE when the applied magnetic field strength is in the range of 50 to 120 mT is substantially the same. Therefore, the relationship between the angle θ and the angle error AE when the applied magnetic field strength is 80 mT shown in FIG. 22 is representative of the relationship between the angle θ and the angle error AE when the applied magnetic field strength is in the range of 50 to 120 mT. It can be said that.

  Here, as an example, in the test before shipment of the magnetic sensor 1 described above, the applied magnetic field strength is 50 mT, and the number m of the plurality of angles θn for obtaining the angle detection values θs is 32. When n is 1, θn is 0 °. A combination of θn and AEn is represented as (θn, AEn). In the test, information of (θn, AEn) is obtained. FIG. 23 shows the relationship between the angle θ created using linear interpolation based on the information of (θn, AEn) and the estimated angle error AEe. In FIG. 23, the horizontal axis indicates the angle θ, and the vertical axis indicates the estimated angle error AEe. The estimated angle error AEe is AEn when the angle θ is θn, and is an angle error estimated by linear interpolation when the angle θ is other than θn. The characteristic line representing the relationship between θ and AEe shown in FIG. 23 is a broken line with (θn, AEn) as a vertex.

  In the first example of the correction process, the above-described correction information (θsn, AEn) is created based on the information (θn, AEn) obtained by the test, and stored in the correction information holding unit 33. When the magnetic sensor 1 is used, the correction processing unit 32 obtains the corrected angle detection value θt corresponding to the input angle detection value θs as described above. Here, the error of the corrected angle detection value θt is defined as a corrected angle error CAE.

  FIG. 24 shows, as an example, the relationship between the angle θ and the corrected angle error CAE when the applied magnetic field strength is 80 mT. In FIG. 24, the horizontal axis represents the angle θ, and the vertical axis represents the corrected angle error CAE. As shown in FIG. 24, the maximum absolute value of the corrected angle error CAE when the applied magnetic field strength is 80 mT is 0.05 ° or less, and when the applied magnetic field strength shown in FIG. 22 is 80 mT. It is significantly smaller than the maximum absolute value of the angle error AE.

  Here, ½ of the difference between the maximum value and the minimum value of the corrected angle error CAE is defined as the amplitude of the corrected angle error CAE. The amplitude of the corrected angle error CAE is equal to or less than the maximum absolute value of the corrected angle error CAE. Therefore, in the example shown in FIG. 24, the amplitude of the corrected angle error CAE when the applied magnetic field strength is 80 mT is 0.05 ° or less.

  The correction processing unit 32 preferably performs the correction process so that the amplitude of the corrected angle error CAE is 0.1 ° or less regardless of the value of the applied magnetic field strength within the sub-range. It is more preferable to perform the correction process so that the amplitude of the corrected angle error CAE is 0.05 ° or less regardless of the value within the range.

  FIG. 25 shows the relationship between the applied magnetic field strength and the amplitude of the corrected angle error CAE in the sub-range 50 to 120 mT. In FIG. 25, the horizontal axis indicates the applied magnetic field strength, and the vertical axis indicates the amplitude of the corrected angle error CAE. As shown in FIG. 25, in the sub-range 50 to 120 mT, the amplitude of the corrected angle error CAE is 0.05 ° or less.

  As described above, the main component of the angle error AE is the angular error quaternary component. The approximate angle error AEs described above is very close to the quaternary component of the angle error. According to the first example of the correction process, the approximated angle error AEs is subtracted from the detected angle value θs to generate the corrected detected angle value θt, and therefore almost includes an error component having a period that is ¼ of the period of the angle θ. It is possible to generate the detected angle detection value θt without correction. Therefore, according to the first example of the correction process, if the variation amount of E4 in the sub-range is 0.1 ° or less, the amplitude of the post-correction angle error CAE in the sub-range is 0.1. If the variation amount of E4 within the sub-range is 0.05 ° or less, the amplitude of the corrected angle error CAE within the sub-range can be 0.05 ° or less.

  Next, a second example of correction processing in the correction processing unit 32 will be described. In the second example of the correction process, the same test as in the first example of the correction process is performed before shipment of the magnetic sensor 1, and the angle θ is changed at regular intervals within the range of 0 ° to 360 °. Thus, the angle error AE at a plurality of angles θ is obtained. Then, the amplitude F of the angle error AE defined as ½ of the difference between the maximum value and the minimum value of the angle error AE is obtained. In the test, the amplitude F is stored in the correction information holding unit 33 as correction information.

  When the magnetic sensor 1 is used, the correction processing unit 32 obtains the corrected angle detection value θt corresponding to the input angle detection value θs by the following equation (4) including the correction information F.

  θt = θs−Fsin4θs (4)

  “Fsin4θs” in Expression (4) corresponds to the approximate angle error AEs in the first example of the correction process. Similar to the first example of the correction process, according to the second example of the correction process, if the variation amount of E4 within the sub-range is 0.1 ° or less, the amplitude of the corrected angle error CAE within the sub-range is as follows. If the variation amount of E4 within the sub-range is 0.05 ° or less, the amplitude of the corrected angle error CAE within the sub-range should be 0.05 ° or less. Can do.

  Note that the content of the correction process is not limited to the first and second examples described above, and the corrected angle detection value θt that hardly includes an error component having a period of ¼ of the period of the angle θ can be generated. That's fine.

[Second Embodiment]
In the magnetic sensor 1 of the second embodiment, the shape of the second surface of the free layer 51 is such that dr is 0.1%, α is 0 °, and the offset angle φ is 10 °. is there. FIG. 26 is a characteristic diagram showing the magnetic field strength dependence of V3r and V5r in the magnetic sensor 1 of the second embodiment and the magnetic sensor of the comparative example. FIG. 27 is a characteristic diagram showing the magnetic field strength dependence of E4 in the magnetic sensor 1 of the second embodiment and the magnetic sensor of the comparative example. In FIG. 26, V3r and V5r in the magnetic sensor 1 of the second embodiment are expressed as V3r (dr = 0.1%, φ = 10 °) and V5r (dr = 0.1%, φ = 10 °). In the comparative magnetic sensor, V3r and V5r are expressed as V3r (dr = 0, φ = 0 °) and V5r (dr = 0, φ = 0 °). In FIG. 27, E4 in the magnetic sensor 1 of the second embodiment is expressed as E4 (dr = 0.1%, φ = 10 °), and E4 in the magnetic sensor of the comparative example is E4 (dr = 0, (φ = 0 °).

  As shown in FIGS. 26 and 27, in the magnetic sensor 1 of the second embodiment, the variation amount of the absolute value of the difference between V3r and V5r is 0.18% or less in the range of applied magnetic field strength of 20 to 70 mT. And the variation amount of E4 is 0.1 ° or less. Further, in the magnetic sensor 1 of the second embodiment, when the applied magnetic field intensity is in the range of 25 to 55 mT, the variation amount of the absolute value of the difference between V3r and V5r is 0.09% or less, and the variation amount of E4 is 0. .05 ° or less. The magnetic sensor 1 of the second example satisfies the requirements for the characteristics of the magnetic sensor 1 according to the present embodiment.

[Third embodiment]
In the magnetic sensor 1 of the third embodiment, the shape of the second surface of the free layer 51 is such that dr is 1%, α is 0 °, and the offset angle φ is 30 °. FIG. 28 is a characteristic diagram showing the magnetic field strength dependence of V3r and V5r in the magnetic sensor 1 of the third embodiment and the magnetic sensor of the comparative example. FIG. 29 is a characteristic diagram showing the magnetic field strength dependence of E4 in the magnetic sensor 1 of the third embodiment and the magnetic sensor of the comparative example. In FIG. 28, V3r and V5r in the magnetic sensor 1 of the third embodiment are expressed as V3r (dr = 1%, φ = 30 °) and V5r (dr = 1%, φ = 30 °), respectively. V3r and V5r in the magnetic sensor are expressed as V3r (dr = 0, φ = 0 °) and V5r (dr = 0, φ = 0 °). In FIG. 29, E4 in the magnetic sensor 1 of the third embodiment is expressed as E4 (dr = 1%, φ = 30 °), and E4 in the magnetic sensor of the comparative example is E4 (dr = 0, φ = 0 °).

  As shown in FIGS. 28 and 29, in the magnetic sensor 1 of the third embodiment, the variation amount of the absolute value of the difference between V3r and V5r is 0.18% or less in the range of applied magnetic field strength of 50 to 150 mT. And the variation amount of E4 is 0.1 ° or less. Further, in the magnetic sensor 1 of the third embodiment, when the applied magnetic field intensity is in the range of 60 to 150 mT, the variation amount of the absolute value of the difference between V3r and V5r is 0.09% or less, and the variation amount of E4 is 0. .05 ° or less. The magnetic sensor 1 of the third example satisfies the requirements for the characteristics of the magnetic sensor 1 according to the present embodiment.

  From the first to third embodiments, by changing the values of dr and α for defining the shape of the second surface of the free layer 51 and the value of the offset angle φ, the difference between the upper limit and the lower limit is 30 mT or more. And it turns out that the subrange which satisfy | fills the requirement that the variation | change_quantity of E4 is 0.1 degrees or less can be moved within the range of 20-150 mT.

  As described above, the magnetic sensor 1 according to the present embodiment is a sub-range in which the applied magnetic field strength is a part of the range of 20 to 150 mT, and the difference between the upper limit and the lower limit is 30 mT or more. The variation amount of E4 when changing within the range satisfies the requirement that it is 0.1 ° or less. Thereby, according to the magnetic sensor 1 which concerns on this Embodiment, the variation | change_quantity of an angle error can be made small in the wide range of applied magnetic field intensity | strength.

  In the present embodiment, when the maximum value of the absolute value of the angle error AE is sufficiently small, for example, 0.1 ° or less or 0.05 ° or less within the sub-range, the arithmetic unit 30 may The detected angle value θs may be output as the value of the angle θ detected by the sensor 1. In this case, the calculation unit 30 may not include the correction processing unit 32 and the correction information holding unit 33.

  In the present embodiment, even if the maximum value of the absolute value of the angle error AE is large, for example, exceeding 0.1 ° within the sub-range, the correction processing unit 32 performs the correction according to the applied magnetic field strength. By performing a correction process that does not differ, the maximum absolute value of the corrected angle error CAE, which is an error of the corrected angle detection value θt, can be reduced within the sub-range.

  It should be noted that the values of dr, α, and φ necessary for satisfying the requirements of the characteristics of the magnetic sensor 1 according to the present embodiment can vary depending on the configuration of the MR element 50 and the like. Therefore, the values of dr, α, and φ are appropriately selected according to the configuration of the MR element 50 and the upper and lower limits of the applied magnetic field strength that defines the subrange.

  The wider the subrange, the better. Therefore, the difference between the upper limit and the lower limit of the subrange that defines the width of the subrange is preferably 40 mT or more, and more preferably 50 mT or more. Here, the difference between the upper limit and the lower limit of the sub-range is 30 mT or more is called the minimum requirement of the sub-range, and the difference between the upper limit and the lower limit of the sub-range is 40 mT or more, the preferable requirement of the sub-range It is said that the difference between the upper limit and the lower limit of the subrange is 50 mT or more as a more preferable requirement of the subrange.

  Further, the variation amount of E4 within the sub-range is preferably as small as possible and is preferably 0.05 ° or less. Here, the variation amount of E4 within the sub-range is 0.1 ° or less is called the minimum requirement of E4, and the variation amount of E4 within the sub-range is 0.05 ° or less. This is a preferable requirement for E4.

  As described above, if the variation amount of the absolute value of the difference between V3r and V5r within the sub-range is 0.18% or less, the variation amount of E4 within the sub-range is 0.1 ° or less. Therefore, in order to satisfy the minimum requirement of E4, it is preferable that the fluctuation amount of the absolute value of the difference between V3r and V5r within the sub-range is 0.18% or less. Further, if the variation amount of the absolute value of the difference between V3r and V5r within the sub-range is 0.09% or less, the variation amount of E4 within the sub-range is 0.05 ° or less. Therefore, in order to satisfy the preferable requirement of E4, it is preferable that the fluctuation amount of the absolute value of the difference between V3r and V5r within the subrange is 0.09% or less.

  The magnetic sensor 1 of the first embodiment and the magnetic sensor 1 of the third embodiment are any of the minimum requirement, preferable requirement, and more preferable requirement of the sub-range, and the minimum requirement and preferable requirement of E4. All the conditions that arbitrarily combined heels are satisfied. The magnetic sensor 1 according to the second embodiment includes a condition that combines any of the minimum requirement, preferred requirement, and more preferable requirement of the sub-range with the minimum requirement of E4, the minimum requirement of the sub-range, and E4. And a combination of preferable requirements.

  In addition, this invention is not limited to the said embodiment, A various change is possible. For example, when the shape of the second surface of the free layer 51 is a four-fold symmetrical shape, the shape of the outer edge 51a of the second surface is not limited to the shape in which r (θa) is represented by Expression (3). For example, the shape of the outer edge 51a of the second surface may be a shape in which r (θa) changes to a triangular wave shape.

  DESCRIPTION OF SYMBOLS 1 ... Magnetic sensor, 2 ... Magnetic field generation part, 3 ... Magnetic field detection part, 10, 20 ... Detection circuit, 14, 24 ... Bridge circuit, 30 ... Operation part, 31 ... Angle detection value calculation part, 32 ... Correction process part, 33 ... Correction information holding unit, 50 ... MR element, 51 ... Free layer, 52 ... Nonmagnetic layer, 53 ... Fixed layer.

16 and 17 are examples shown for explaining the tendency of the change in the magnetic field strength dependency of V3r, V5r, and E4 when at least one of the strain ratio dr and the strain direction α is changed. . Although not shown in FIGS. 16 and 17, when dr is changed while α is constant, the change in the magnetic field strength dependence of V3r, V5r, and E4, which tends to be described below, becomes more prominent as dr increases. As dr decreases, the magnetic field strength dependence of V3r, V5r, and E4 approaches the magnetic field strength dependence of V3r, V5r, and E4 when dr is zero, respectively.

Claims (10)

A magnetic sensor for generating an angle detection value having a correspondence relationship with an angle formed by a direction of a detected magnetic field at a reference position with respect to a reference direction,
A magnetic field detection unit and a calculation unit;
The magnetic field detection unit includes a plurality of magnetoresistive elements that detect the detected magnetic field, and the first signal having a correspondence relationship with the angle formed by the direction of the detected magnetic field with respect to the first direction and the detected signal Outputting a second signal having a correspondence relationship with an angle formed by the direction of the detected magnetic field with respect to the second direction;
Each of the plurality of magnetoresistive elements includes a magnetization fixed layer whose magnetization direction is fixed, a free layer whose magnetization direction changes according to the direction of the detected magnetic field, and between the magnetization fixed layer and the free layer A non-magnetic layer disposed on
The calculation unit calculates the angle detection value based on the first and second signals,
When the direction of the detected magnetic field rotates at a predetermined period, the angle detection value includes an angle error component that changes at a quarter of the predetermined period;
The angle error when the intensity of the magnetic field to be detected in the magnetic field detection unit is a sub-range that is a part of a range of 20 to 150 mT and the difference between the upper limit and the lower limit changes within a sub-range that is 30 mT or more. A magnetic sensor characterized in that the fluctuation amount of the maximum absolute value of the component is 0.1 ° or less. When the direction of the detected magnetic field rotates at the predetermined period, the first signal is a first ideal component that periodically changes to draw an ideal sine curve, and the first ideal component. A first third harmonic component that is an error component corresponding to the third harmonic with respect to and a first fifth harmonic component that is an error component corresponding to the fifth harmonic with respect to the first ideal component. And the second signal is a second ideal component that periodically changes to draw an ideal sine curve, and an error component corresponding to a third harmonic with respect to the second ideal component. And a second fifth harmonic component that is an error component corresponding to the fifth harmonic with respect to the second ideal component,
When the ratio of the first third harmonic component to the first ideal component when the first ideal component takes the maximum value is the first ratio, and the first ideal component takes the maximum value The ratio of the first fifth harmonic component to the first ideal component is a second ratio, and the second ideal component with respect to the second ideal component when the second ideal component takes a maximum value. The ratio of the third harmonic component is the third ratio, and the ratio of the second fifth harmonic component to the second ideal component when the second ideal component takes the maximum value is the fourth ratio. And an average value of the first ratio and the third ratio is a third harmonic component ratio, and an average value of the second ratio and the fourth ratio is a fifth harmonic component ratio. The third high level when the strength of the detected magnetic field in the magnetic field detecting unit changes within the sub-range. The magnetic sensor according to claim 1, wherein the amount of fluctuation of the absolute value of the difference between the a wave component ratios fifth harmonic component ratio is less than 0.18%.   The calculation unit includes an angle detection value calculation unit that calculates the angle detection value, and a correction processing unit that performs correction processing on the angle detection value to generate a corrected angle detection value, and the corrected angle 3. The magnetic sensor according to claim 1, wherein the maximum absolute value of the detected value error is smaller than the maximum absolute value of the detected angle error. 4.   The correction processing unit is ½ of the difference between the maximum value and the minimum value of the corrected angle detection value regardless of the value of the detected magnetic field in the magnetic field detection unit within the sub-range. The magnetic sensor according to claim 3, wherein the correction process is performed so that the angle is 0.1 ° or less.   The fluctuation amount of the maximum value of the absolute value of the angle error component when the intensity of the detected magnetic field in the magnetic field detection unit changes within the sub-range is 0.05 ° or less. The magnetic sensor according to 1. When the direction of the detected magnetic field rotates at the predetermined period, the first signal is a first ideal component that periodically changes to draw an ideal sine curve, and the first ideal component. A first third harmonic component that is an error component corresponding to the third harmonic with respect to and a first fifth harmonic component that is an error component corresponding to the fifth harmonic with respect to the first ideal component. And the second signal is a second ideal component that periodically changes to draw an ideal sine curve, and an error component corresponding to a third harmonic with respect to the second ideal component. And a second fifth harmonic component that is an error component corresponding to the fifth harmonic with respect to the second ideal component,
When the ratio of the first third harmonic component to the first ideal component when the first ideal component takes the maximum value is the first ratio, and the first ideal component takes the maximum value The ratio of the first fifth harmonic component to the first ideal component is a second ratio, and the second ideal component with respect to the second ideal component when the second ideal component takes a maximum value. The ratio of the third harmonic component is the third ratio, and the ratio of the second fifth harmonic component to the second ideal component when the second ideal component takes the maximum value is the fourth ratio. And an average value of the first ratio and the third ratio is a third harmonic component ratio, and an average value of the second ratio and the fourth ratio is a fifth harmonic component ratio. The third high level when the strength of the detected magnetic field in the magnetic field detecting unit changes within the sub-range. The magnetic sensor according to claim 5, wherein the amount of fluctuation of the absolute value of the difference between the a wave component ratios fifth harmonic component ratio is less than 0.09%.   The calculation unit includes an angle detection value calculation unit that calculates the angle detection value, and a correction processing unit that performs correction processing on the angle detection value to generate a corrected angle detection value, and the corrected angle 7. The magnetic sensor according to claim 5, wherein a maximum absolute value of the detected value error is smaller than a maximum absolute value of the detected angle error.   The correction processing unit is ½ of the difference between the maximum value and the minimum value of the corrected angle detection value regardless of the value of the detected magnetic field in the magnetic field detection unit within the sub-range. The magnetic sensor according to claim 7, wherein the correction process is performed so that the angle becomes 0.05 ° or less.   The magnetic sensor according to claim 1, wherein the second direction is orthogonal to the first direction. The magnetic field detection unit includes a first detection circuit that outputs the first signal, and a second detection circuit that outputs the second signal,
Each of the first detection circuit and the second detection circuit includes a magnetoresistive effect element array configured by connecting two or more of the plurality of magnetoresistive effect elements in series,
The free layer of each of the plurality of magnetoresistive elements has a first surface in contact with the nonmagnetic layer and a second surface opposite to the first surface, and the second surface is 5 times or more. Having a four-fold rotational symmetry shape that is not rotationally symmetric,
The number of the two or more magnetoresistive elements constituting the magnetoresistive element array is an even number,
The two or more magnetoresistive elements constituting the magnetoresistive element array include one or more pairs of magnetoresistive elements,
The magnetization direction of the magnetization fixed layer in the two magnetoresistive elements constituting the pair has a predetermined relative angle excluding 0 ° and 180 °,
In the first detection circuit, the first direction is an intermediate direction of the magnetization direction of the magnetization fixed layer in the two magnetoresistive effect elements constituting the pair or a direction opposite thereto.
In the second detection circuit, the second direction is an intermediate direction of the magnetization direction of the magnetization fixed layer in the two magnetoresistive elements constituting the pair or a direction opposite thereto. The magnetic sensor according to claim 1.

Images