WO2010113820A1 - 回転角度検出装置 - Google Patents
回転角度検出装置 Download PDFInfo
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- WO2010113820A1 WO2010113820A1 PCT/JP2010/055447 JP2010055447W WO2010113820A1 WO 2010113820 A1 WO2010113820 A1 WO 2010113820A1 JP 2010055447 W JP2010055447 W JP 2010055447W WO 2010113820 A1 WO2010113820 A1 WO 2010113820A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/142—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices
- G01D5/145—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage using Hall-effect devices influenced by the relative movement between the Hall device and magnetic fields
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- the present invention relates to a rotation angle detection apparatus including a magnetic sensor using a magnetoresistive effect element constituted by a spin valve type giant magnetoresistive effect film, and a rotation angle with reduced angular error due to manufacturing variations of the magnetic sensor.
- the present invention relates to a detection device.
- a magnetic sensor using a magnetoresistive effect element that can detect a change in rotation angle and the like in a non-contact manner is required to have good detection sensitivity for a rotating magnetic field.
- a high-sensitivity magnetoresistive element an anisotropic magnetization fixed layer (simply referred to as a “fixed layer”), a nonmagnetic intermediate layer formed on the fixed layer that breaks magnetic coupling, and a nonmagnetic intermediate layer
- a spin-valve giant magnetoresistive (SVGMR) film having a free layer whose magnetization direction rotates in an arbitrary direction by an external magnetic field formed thereon is used.
- JP 2001-159542 A includes a substrate having a magnetoresistive element, a wiring substrate that connects the magnetoresistive element to form a bridge circuit, and a sensor holder that holds the substrate and the wiring substrate.
- a rotation angle sensor is disclosed in which the substrate is provided on the holder by a multiple of 4 and at least two substrates are inclined at 80 to 100 ° on the wiring board surface. In this rotation angle sensor, four elements cut out from the same wafer are bridge-connected, but variations in the wafer plane cannot be absorbed.
- Special table 2003-502876 discloses a method of manufacturing an element having a plurality of magnetic sensing directions on the same wafer.
- the fixed layer magnetization direction is set to a desired direction by applying an external magnetic field while locally heating the element with a heater.
- 41 and 42 show the arrangement of elements obtained by this method. As shown in an enlarged view in FIG. 42, there is an element having an antiparallel pinned layer magnetization direction in the arrow direction 100, but an antiparallel pinned layer magnetization direction in the arrow direction 100 ′ orthogonal to the arrow direction 100. There is no element to have.
- Japanese Patent Laid-Open No. 2005-024287 discloses an element in which patterns whose longitudinal directions are different by 90 ° are connected in order to cancel the AMR effect.
- the Japanese Patent No. 3587678 proposes a semicircular or spiral element pattern with reduced H k. However, these configurations simply cancel the AMR effect or reduce H k, and do not perform signal processing to reduce the angle error.
- an object of the present invention is to provide a rotation angle detection device including a magnetic sensor using an SVGMR element, which can reduce an angle error due to manufacturing variations of the magnetic sensor.
- a first rotation angle detection device of the present invention includes a magnet rotor, a magnetic sensor that detects a direction of magnetic flux from the magnet rotor, a correction circuit, and an angle calculation circuit.
- the magnetic sensor has a bridge circuit X in which four magnetoresistive elements are connected and a bridge circuit Y in which four magnetoresistive elements are connected, Each of the magnetoresistive effect elements is sandwiched between a fixed layer having a magnetization direction fixed in one direction, a free layer variable so that the magnetization direction is aligned with the external magnetic field direction, and the fixed layer and the free layer It has a spin valve type giant magnetoresistive film having an intermediate layer,
- the correction circuit calculates a difference (Vx ⁇ Vy) and a sum (Vx + Vy) from the output voltage Vx of the bridge circuit X and the output voltage Vy of the bridge circuit Y, and aligns the amplitudes of both the same.
- the angle calculation circuit performs an arctangent calculation on (Vx ⁇ Vy) ′ / (Vx + Vy) ′ obtained from the (Vx ⁇ Vy) ′ signal and the (Vx + Vy) ′ signal having the same amplitude output from the correction circuit.
- the rotation angle of the magnet rotor is obtained by the following.
- a second rotation angle detection device of the present invention comprises a magnet rotor, a magnetic sensor for detecting the direction of magnetic flux from the magnet rotor, an operational amplifier circuit, a correction circuit, and an angle calculation circuit.
- the magnetic sensor has a bridge circuit X in which four magnetoresistive elements are connected and a bridge circuit Y in which four magnetoresistive elements are connected, Each of the magnetoresistive effect elements is sandwiched between a fixed layer having a magnetization direction fixed in one direction, a free layer variable so that the magnetization direction is aligned with the external magnetic field direction, and the fixed layer and the free layer It has a spin valve type giant magnetoresistive film having an intermediate layer,
- the operational amplifier circuit calculates a difference (Vx ⁇ Vy) and a sum (Vx + Vy) from the output voltage Vx of the bridge circuit X and the output voltage Vy of the bridge circuit Y,
- the correction circuit has the same amplitude of the (Vx ⁇ Vy) signal and the (Vx + Vy)
- At least one longitudinal direction of the magnetoresistive effect element is inclined by an acute angle ⁇ that satisfies a condition of 36 ° ⁇ ⁇ ⁇ 45 ° with respect to the magnetization direction of the fixed layer.
- two magnetoresistive elements are inclined by an acute angle ⁇ with respect to the fixed layer magnetization direction, and the other two are inclined by an acute angle ⁇ . It is preferable.
- the pinned layer magnetization directions of the two magnetoresistive elements constituting the half bridges of the bridge circuit X and the bridge circuit Y are preferably antiparallel.
- the longitudinal direction of the magnetoresistive effect element of the bridge circuit X and the longitudinal direction of the magnetoresistive effect element of the bridge circuit Y are orthogonal to each other.
- Pinned layers of the spin-valve giant magnetoresistive film - the exchange coupling magnetic field H int free layers is preferably within ⁇ 0.4 kA / m.
- the rotation angle detection device of the present invention aligns the amplitudes of the (Vx ⁇ Vy) signal and the (Vx + Vy) signal obtained from the output voltage Vx of the bridge circuit X and the output voltage Vy of the bridge circuit Y, and then (Vx ⁇ By calculating the arc tangent of (Vy) / (Vx + Vy), it is possible to reduce angular errors due to manufacturing variations of magnetic sensors.
- Magnetoresistive element is a graph showing the relationship between the shape anisotropy direction theta dip and angle error theta err variation width [Delta] [theta] err.
- 6 is a graph showing the relationship between an angle ⁇ app of an external magnetic field H app with respect to a reference axis and an angle error ⁇ err for magnetoresistive elements of Sample 1-1 and Sample 1-4.
- 6 is a graph showing the relationship between ⁇ app and ⁇ err for magnetoresistive elements of Sample 1-4 and Sample 1-5.
- FIG. 5 is a graph showing the relationship between ⁇ app and ⁇ err for magnetoresistive elements of Sample 1-1 and Sample 1-7. It is a graph which shows the harmonic component of the magnetoresistive effect element of sample 1-1, sample 1-4, sample 1-5, and sample 1-7.
- 7 is a graph showing harmonic generation rates of magnetoresistive effect elements of Sample 1-1, Sample 1-4, Sample 1-5, and Sample 1-7.
- 6 is a graph showing the relationship between ⁇ err and ⁇ dip of a magnetoresistive element in each anisotropic magnetic field H k when the shape anisotropy H kd of the magnetoresistive element is fixed.
- FIG. 6 is a graph showing harmonic components of Sample 2-1, Sample 2-5, and Sample 2-7 in which magnetoresistive elements are arranged in parallel. It is a graph which shows the harmonic component of sample 3-4 and sample 3-5 of a magnetoresistive effect element non-parallel arrangement. It is a graph which shows the harmonic component of sample 2-5 and sample 3-5. It is a graph which shows the relationship between ( DELTA) (theta) err of a magnetoresistive effect element and Hint -R5 in each Hint-R1 . It is the schematic which shows an example of arrangement
- FIG. 1 shows an example of a rotation angle detection device.
- This apparatus includes a magnetic sensor 31 formed by bridge-connecting SVGMR elements, a disk-shaped permanent magnet 33 that is magnetized in two diametrical directions facing the magnetic sensor 31, a jig 34 for fixing the permanent magnet 33, and a jig 34. And a rotating shaft 34b integrated with each other.
- the permanent magnet 33 rotates, the leakage magnetic field changes.
- an alternate long and short dash line indicates a rotation center axis, and an arrow 32 between the permanent magnet 33 and the magnetic sensor 32 indicates a line of magnetic force.
- a magnetic sensor 31 detects a magnetic field change in the in-plane direction of the SVGMR element.
- the magnetic sensor is moved from 31 to 31 ′.
- the substrate surface of the magnetic sensor 31 ′ is opposed to the outer peripheral surface of the permanent magnet 33 and has a central axis parallel to the rotational central axis.
- FIG. 2 schematically shows an example of the layer structure of the SVGMR film, but the magnification of the thickness of each layer is not necessarily constant.
- the SVGMR film has a base film 11, a fixed layer 12, an intermediate layer 13, a free layer 14, and a protective layer 15 formed in order on the substrate 10.
- the fixed layer 12 includes an antiferromagnetic layer 121, a first ferromagnetic layer 122, an antiparallel coupling layer 123, and a second ferromagnetic layer 124 in order from the bottom, and the free layer 14 includes two or more ferromagnetic layers 141. 142.
- the fixed layer 12 has a magnetization direction (unidirectional magnetic anisotropy) fixed in one direction. The electrical resistance changes according to the angle formed by the magnetization direction of the fixed layer and the magnetization direction of the free layer 14 that rotates freely by an external magnetic field.
- Fig. 3 shows another example of the layer structure of the SVGMR film. Since this SVGMR film has a layer structure obtained by removing the antiferromagnetic layer 121 from the SVGMR film shown in FIG. 2, the unidirectional magnetic anisotropy of the fixed layer 12 is only due to the antiferromagnetic coupling of the ferromagnetic layers 122 and 124. To express.
- the SVGMR film shown in Fig. 3 not only does not require a heat treatment step to regularize the antiferromagnetic layer and magnetize the fixed layer, but also sets the anisotropy of the fixed layer in any direction during the film formation process. can do.
- the magnetization direction of the fixed layer is changed to the direction of the applied magnetic field by applying a magnetic field when forming the two ferromagnetic layers used for the fixed layer, at least when forming the ferromagnetic layer in contact with the intermediate layer 13.
- a magnetic field when forming the two ferromagnetic layers used for the fixed layer, at least when forming the ferromagnetic layer in contact with the intermediate layer 13.
- elements having four fixed layer magnetization directions are formed on the same wafer by stacking SVGMR films having different fixed layer magnetization directions four times via an insulating layer.
- FIG. 4 schematically shows the magnetic energy received by the SVGMR element (magnetoresistance effect element).
- ⁇ M represents the magnetization direction of the entire element
- ⁇ dip represents the shape anisotropy direction
- ⁇ free represents the uniaxial magnetic anisotropy direction of the free layer.
- E total E kd + E k + E ex + E z
- E kd shape magnetic anisotropy energy of the SVGMR element
- E k is the magnetic anisotropy energy of the free layer
- E ex is the interlayer exchange coupling energy of the SVGMR film
- E z is the SVGMR film Zeeman energy, expressed by the following equations (2) to (5).
- E kd K ud sin 2 ( ⁇ M ⁇ dip ) ⁇ ⁇ ⁇ (2)
- E k K u sin 2 ( ⁇ M ⁇ free ) (3)
- E ex -H int ⁇ M S cos ( ⁇ M ⁇ free ) ⁇ ⁇ ⁇ (4)
- E z ⁇ H app ⁇ M S cos ( ⁇ app ⁇ M ) (5)
- M S indicates the magnetization of the free layer, represented by the respective magnetic anisotropy constant K ud and K u is the following formula (6) and (7).
- K ud (H kd ⁇ M S ) / 2 ⁇ ⁇ ⁇ (6)
- K u (H k ⁇ M S ) / 2 (7)
- the direction ⁇ M of M is obtained when E total is minimum, and when this ⁇ M is used, the resistance R of the SVGMR element is expressed by the following equation (8).
- R min is the minimum resistance value of the SVGMR element
- dR is the resistance change amount due to the GMR effect
- dR ′ is the resistance change amount due to the AMR effect.
- the first half of equation (8) represents the resistance change due to the GMR effect
- the second half represents the resistance change due to the AMR effect.
- the shape anisotropy direction ⁇ dip is determined by the shape of the SVGMR element and coincides with the longitudinal direction of the element.
- ⁇ dip Substantially coincides with the direction 222 (the longitudinal direction of the element) of the current flowing between the terminals 223 and 223 ′.
- SVGMR elements 241 and 251 having a shape in which a plurality of circles are connected as shown in FIGS.
- ⁇ dip is the direction of current 222 flowing between terminals 223 and 223 ′ (the length of the element) Direction).
- SVGMR elements with a shape in which a plurality of circles with cutouts are connected, a shape in which a plurality of semicircles are connected, and a shape in which a plurality of polygons are connected Similarly, in the case of 261, 271, 281, 291, 301, 311, 321, 331, ⁇ dip coincides with the current direction 222 (the longitudinal direction of the element).
- FIG. 11 shows an equivalent circuit of a magnetic sensor formed by bridge-connecting SVGMR elements.
- the pinned layer magnetization direction of each element is indicated by an arrow in the figure.
- Elements 21a and 21c, elements 21b and 21d, elements 31a and 31c, and elements 31b and 31d have the same fixed layer magnetization direction.
- the elements 21a and 21b and the elements 31a and 31b have anti-parallel (180 ° reverse direction) fixed layer magnetization directions, and the elements 21a and 31a have fixed layer magnetization directions different by 90 °.
- the elements 21a to 21d constitute a bridge circuit X
- the elements 31a to 31d constitute a bridge circuit Y.
- the elements 21a and 31a, the elements 21b and 31b, the elements 21c and 31c, and the elements 21d and 31d are arranged so as to be orthogonal to each other.
- the angle between the element and the fixed layer magnetization direction refers to the angle between the longitudinal direction of the element and the fixed layer magnetization direction.
- the voltages Vx 1 , Vx 2 , Vy 1 , and Vy 2 output from the bridge circuit are expressed by the following equations (9) to (12), respectively. (However, R 21a to R 21d and R 31a to R 31d represent the resistances of the elements 21a to 21d and 31a to 31d, respectively.)
- the output voltage Vx from Vx 1 -Vx 2 is obtained, the output voltage Vy from Vy 1 -Vy 2 is obtained.
- Vx and Vy have approximately sine wave or cosine wave waveforms.
- the difference between the angle ⁇ calc obtained by the arctangent calculation from Vx and Vy and the angle ⁇ app of H app with respect to the reference axis is the angle error ⁇ err of the magnetic sensor.
- the signal processing circuit used in the rotation angle detection device of the present invention includes (a) a first signal processing circuit including a correction circuit and an angle calculation circuit, (b) an operational amplifier circuit, There is a second signal processing circuit including a correction circuit and an angle calculation circuit.
- the phase difference between the output Vx of the bridge circuit X and the output Vy of the bridge circuit Y may not be ⁇ / 2 but ⁇ / 2 ⁇ ⁇ due to manufacturing variations.
- FIG. 12 shows the angle errors ⁇ err and ⁇ app (reference axis when ⁇ is 0 ° and 1 ° in the phase difference ⁇ / 2 ⁇ ⁇ between the bridge circuit X and the bridge circuit Y of Sample 3-4. H app angle with respect to). It can be seen from FIG. 12 that the angle error increases with ⁇ .
- Vx ⁇ Vy and (Vx + Vy) are two signals having a phase difference of ⁇ / 2 as shown in equations (15) and (16).
- Vx ⁇ Vy 2 sin ( ⁇ / 4 ⁇ / 2) sin ( ⁇ app ⁇ / 4 + ⁇ / 2)
- Vx + Vy 2 cos ( ⁇ / 4 ⁇ / 2) cos ( ⁇ app ⁇ / 4 + ⁇ / 2)
- Equation (17) shows that ⁇ app is detected without error although the initial phase is different.
- FIG. 13 shows the relationship between the angle errors ⁇ err and ⁇ app when the phase shift is corrected.
- the corrected angle error ⁇ err returns to the waveform of ⁇ err of the sample 3-4 shown in FIG. 12, and the phase shift can be completely cancelled.
- FIG. 14 shows a first signal processing circuit 40 that cancels the phase shift.
- the rotation angle detection device includes a rotor having a dipole magnet 33 fixed to a shaft, and a magnetic sensor 31 disposed in the vicinity of the dipole magnet 33.
- the signal processing circuit 40 includes operational amplifiers 41a and 41b that input the output voltages Vx and Vy of the bridge circuits X and Y in the magnetic sensor 31, an AD conversion correction circuit 42 that receives the outputs of the operational amplifiers 41a and 41b, and AD conversion correction. And an angle calculation circuit 43 for inputting the output of the circuit.
- the operational amplifier 41a calculates Vx ⁇ Vy from the output voltages Vx and Vy
- the operational amplifier 41b calculates Vx + Vy from the output voltages Vx and Vy.
- the AD conversion correction circuit 42 receives the (Vx ⁇ Vy) and (Vx + Vy) signals of the operational amplifiers 41a and 41b, performs analog-to-digital conversion, corrects them to have the same amplitude, and has the same amplitude.
- the (Vx ⁇ Vy) ′ signal and the (Vx + Vy) ′ signal are output.
- the angle calculation circuit 43 inputs the (Vx ⁇ Vy) ′ signal and the (Vx + Vy) ′ signal output from the correction circuit 42 and performs an arctangent calculation of (Vx ⁇ Vy) ′ / (Vx + Vy) ′ to obtain an angle ⁇ Ask for.
- the amplitude of both the (Vx ⁇ Vy) signal and the (Vx + Vy) signal is corrected, and the amplitude of one signal
- the amplitudes of the (Vx ⁇ Vy) signal and the (Vx + Vy) signal input to the correction circuit 42 are respectively multiplied by C 1 and C 2 to obtain a C 1 (Vx ⁇ Vy) signal and C having the same amplitude. 2 Use the (Vx + Vy) signal.
- the amplitude of the (Vx ⁇ Vy) signal input to the correction circuit 42 is multiplied by C 3 to obtain a C 3 (Vx ⁇ Vy) signal and a (Vx + Vy) signal having the same amplitude.
- FIG. 15 shows a second signal processing circuit 40 ′ that cancels the phase shift.
- the rotation angle detection device is the same as that shown in FIG.
- the signal processing circuit 40 ′ inputs the output voltages Vx and Vy from the bridge circuits X and Y in the magnetic sensor 31, performs analog-digital conversion, calculates (Vx ⁇ Vy) and (Vx + Vy), and their amplitudes.
- AD conversion correction circuit 42 'for correction and AD conversion correction circuit 42' output (Vx-Vy) ', (Vx + Vy)' are input, and arc tangent calculation of (Vx-Vy) '/ (Vx + Vy)' And an angle calculation circuit 43 for obtaining the angle ⁇ .
- the functions of the operational amplifiers 41a and 41b and the AD conversion correction circuit in the first signal processing circuit 40 are performed by the AD conversion correction circuit 42 ′.
- FIG. 16 shows an example of a magnetic sensor having a bridge circuit X and a bridge circuit Y of SVGMR elements.
- the illustrated element arrangement corresponds to a sample 1-3 in Table 1 described later.
- the bridge circuit X four rectangular SVGMR elements 201a to 201d are formed on the substrate, the elements 201b and 201c are connected to the power supply terminal Vcc, and the elements 201a and 201d are connected to the ground terminal GND.
- cage, elements 201a and 201b are connected to one output terminal Vx 1, element 201c and 201d are connected to the other output terminal Vx 2.
- the longitudinal directions of the elements 201a to 201d are inclined by angles ⁇ dip-R1 to ⁇ dip-R4 with respect to the axis 202 parallel to the fixed layer magnetization direction indicated by the arrow.
- the bridge circuit Y four rectangular SVGMR elements 203a to 203d are formed on the substrate, and are orthogonal to the corresponding elements 201a to 201d of the bridge circuit X, respectively.
- the pinned layer magnetization direction of each element is parallel to the axis line 204 orthogonal to the axis line 202, but the longitudinal direction is inclined by angles ⁇ dip-R5 to ⁇ dip-R8 .
- the longitudinal directions of elements having the same fixed layer magnetization direction are parallel.
- ⁇ dip-R1 to ⁇ dip-R4 and ⁇ dip-R5 to ⁇ dip-R8 of each element 201a to 201d and 203a to 203d satisfy the following relationship.
- ⁇ dip-R1 of element 201a ⁇ dip-R3 of element 201c
- ⁇ dip-R2 of element 201b ⁇ dip-R4 of element 201d
- ⁇ dip-R1 - ⁇ dip-R2
- ⁇ dip-R5 of element 203a ⁇ dip-R7 of element 203c
- dip-R6 of element 203b ⁇ dip-R8 of element 203d
- ⁇ dip-R5 - ⁇ dip-R6
- the right direction of the bridge circuit X is 0 ° and the upward direction of the bridge circuit Y is 0 °.
- the ⁇ dip of each element 201a to 201d and 203a to 203d is shown in Table 1 (the counterclockwise angle of the element is represented by “+”)
- the value of ⁇ dip ⁇ 180 ° is shown in parentheses), and the influence of the arrangement angle ⁇ dip on the change width ( ⁇ err ) of the angle error ⁇ err was obtained by simulation.
- ⁇ err is a value obtained by subtracting the minimum value from the maximum value of ⁇ err when ⁇ app is changed from 0 ° to 360 °.
- Table 2 shows ⁇ err when the arrangement angle ⁇ dip-R1 of the element 201a shown in Table 1 is 35 ° to 45 °.
- ⁇ dip-R1 of the element 201a was + 40 ° and + 140 ° ( ⁇ 40 °) (samples 1-4 and 1-9)
- ⁇ err was 0.0762 ° and the minimum.
- the arrangement angle ⁇ dip-R1 of the element 201a is + 140 ° ( ⁇ 40 °)
- the arrangement angle ⁇ dip-R2 of the counterpart element 201b constituting the half bridge is ⁇ 140 ° (+ 40 °).
- ⁇ err was about 1.8 °.
- ⁇ err greatly depends on ⁇ dip, and the angle error changes greatly depending on the element arrangement. From FIG. 17 and Table 2, by setting the element arrangement angle ⁇ dip so as to satisfy the condition of 36 ° ⁇ ⁇ dip-R1 ⁇ 45 °, a magnetic sensor with a small angle error and hence a small output distortion can be obtained. I understand.
- a preferable ⁇ dip is 37 to 43 °, and a more preferable ⁇ dip is 39 to 42 °.
- an angle error (magnetic sensor's magnetic sensor H int and anisotropy magnetic field H k ) varies due to variations in the magnetic characteristics of the SVGMR element itself.
- the error of the rotation angle obtained from the output increases.
- the angle error in the output of the magnetic sensor can be reduced by setting 36 ° ⁇ ⁇ dip-R1 ⁇ 45 °.
- Sample 1-5 corresponds to the element arrangement described in JP-T-2003-502876 and JP-A-2005-024287.
- ⁇ err is about 0.04 ° at the maximum in Sample 1-4, but about 0.9 ° to 1.0 ° at the maximum in Sample 1-1 and Sample 1-7, and about 0.19 ° in Sample 1-5.
- Sample 1-4 and Sample 1-5 differ greatly in ⁇ err even if the difference in ⁇ dip is 5 °.
- Sample 1-1 and Sample 1-7 differ in the dependence of ⁇ err on ⁇ app because the relationship between ⁇ dip and the fixed layer magnetization direction is different despite the similar element arrangement. From these results, it can be seen that ⁇ err varies greatly depending on the relationship between ⁇ dip and the fixed layer magnetization direction.
- the main causes of the generation of the fourth harmonic are the element shape and the magnetic anisotropy of the free layer, that is, H kd and H k are considered.
- H k is uniquely determined by the material used for the free layer.
- H k of 0.16 kA / m H k of NiFe generally used in the free layer
- the coercive force or the like which affects the hysteresis is changed there is a possibility.
- the macroscopic H k can be reduced, but it may cause an increase in shunt loss and a decrease in sensitivity due to an increase in film thickness.
- the SVGMR element has a finite length, it is not easy to make H kd depending on the element shape close to zero.
- ⁇ dip 40 °
- ⁇ err increases with respect to H k variations due to variations in SVGMR film characteristics and H kd variations due to element shapes Therefore, a rotation angle detection device with high detection accuracy can be obtained.
- Example 2 In order to suppress the power consumption of the magnetic sensor by increasing the resistance of the SVGMR element, the longitudinal dimension of the element may be set to several tens to 100 ⁇ m. When the element is lengthened in this way, the shape anisotropy of the free layer of the SVGMR film increases, and the AMR effect of the free layer cannot be ignored. Therefore, in the magnetic sensor having the same element arrangement as in Example 1, ⁇ dip is changed as shown in Table 3 (the counterclockwise angle of the element is represented by “+”, and the value of ⁇ dip ⁇ 180 ° is shown in parentheses). Thus, ⁇ err with and without the AMR effect was obtained by simulation. The results are shown in FIG.
- Equation (8) the resistance value contributing to AMR is assumed to be 7500 ⁇ from the film thickness ratio of the free layer to the SVGMR film and the resistivity of NiFe film, and dR ′ is 22.5 ⁇ assuming that the AMR ratio is 0.3%. I estimated. Sample 2-5 is an element arrangement described in JP-T-2003-502876 and JP-A-2005-024287.
- the current is reversed in each element pair (for example, 201a and 201c, and 201b and 201d) in the same bridge, so the contribution of the AMR effect to the angle error depends on the direction in which the sense current flows and the free layer Depends on the easy axis of magnetization.
- Fig. 26 shows a magnetic sensor effective in suppressing the AMR effect.
- the pinned layer magnetization direction of the bridge circuit X is a horizontal direction
- the pinned layer magnetization direction of the bridge circuit Y is a vertical direction.
- the elements 211a and 211c have the same fixed layer magnetization direction
- the elements 211b and 211d have the same fixed layer magnetization direction.
- the longitudinal directions of the elements having the same fixed layer magnetization direction in each bridge are non-parallel.
- Each of the elements 211a to 211d and 213a to 213d has a rectangular shape as in FIG.
- ⁇ dip of each element in the bridge circuit X (elements 211a to 211d) and the bridge circuit Y (elements 213a to 213d) is as follows.
- ⁇ dip-R1 of element 211a ⁇ dip-R4 of element 211d
- ⁇ dip-R2 of element 211b ⁇ dip-R3 of element 211c
- ⁇ dip-R1 - ⁇ dip-R2
- ⁇ dip-R5 of element 213a ⁇ dip-R8 of element 213d
- dip-R6 of element 213b ⁇ dip-R7 of element 213c
- ⁇ dip-R5 - ⁇ dip-R6
- the right direction of the bridge circuit X is 0 ° and the upward direction of the bridge circuit Y is 0 °
- the ⁇ dip of each element 211a to 211d and 213a to 213d is shown in Table 4 (the clockwise angle of the element is “+”)
- the value of ⁇ dip ⁇ 180 ° is shown in parentheses)
- the ⁇ dip dependence of ⁇ err taking into account the AMR effect was obtained by simulation.
- Table 5 shows ⁇ err when the arrangement angle ⁇ dip-R1 of the element 211a is 35 to 45 °.
- the angle error is smaller in the bridge circuit in which ⁇ dip is 38 ° or more and less than 45 ° than in the bridge circuit in which ⁇ dip is 45 °.
- a preferable ⁇ dip is 39 to 44 °, and a more preferable ⁇ dip is 40 to 43 °.
- Fig. 28 shows the harmonic analysis results of Sample 2-1, Sample 2-5, and Sample 2-7 with the elements arranged in parallel, and harmonic analysis of Sample 3-4 and Sample 3-5 with the elements arranged in parallel The results are shown in FIG.
- all the harmonics appearing in Sample 2-1 and Sample 2-7 having a relatively small ⁇ err are fourth order.
- Sample 2-5 with a large ⁇ err contains all the harmonics up to the fifth order, and it can be seen that the first and third order harmonics are particularly large. From Eq.
- the AMR effect should appear as the 4th harmonic, but it is surmised that the 3rd order has increased due to the arrangement of the elements.
- Samples 3-4 and 3-5 in which the elements are arranged non-parallel, have almost no harmonics other than the fourth order, and Sample 3-4 is significantly smaller in the fourth order harmonics.
- Figure 30 is theta illustrating dip and the sample 2-5 of the element parallel arrangement at 45 °, theta harmonics of the sample 3-5 of dip is non-parallel arranged elements at 45 °.
- the harmonics other than the fourth order were almost 0, and the fourth-order harmonic was also almost half of Sample 2-5 in which the elements were arranged in parallel. From this, it can be seen that to reduce ⁇ err , it is necessary to make the first-order or third-order harmonic substantially zero and to significantly reduce the fourth-order harmonic.
- Example 3 The magnetic property that is most likely to vary in the SVGMR film is H int (magnetic field acting between the fixed layer and the free layer via the intermediate layer). H int tends to fluctuate depending on the film thickness variation of the intermediate layer, the so-called “orange peel effect” due to the surface roughness of the intermediate layer, the operating temperature, the environmental temperature, and the like. Therefore, in order to obtain the relationship between H int and ⁇ err under the optimum element arrangement conditions (sample 3-4), H int (H int-R5 ) of element 213a in the magnetic sensor shown in FIG.
- H int H int-R5
- H int-R1 is 0 kA / m, 0.08 kA / m, 0.16 kA / m, 0.40 kA / m, and 0.80 kA /
- H int-R1 is 0 kA / m, 0.08 kA / m, 0.16 kA / m, 0.40 kA / m, and 0.80 kA /
- ⁇ err was smaller when H int-R1 was smaller, and was almost minimum when the sign of H int-R5 was reversed.
- H int-R1 is 0.16 kA / m or less
- ⁇ err is 1 ° or less
- H int-R1 is 0.4 kA / m or more and H int-R5 is within ⁇ 0.4 kA / m
- ⁇ err is 1. It was less than °.
- a magnetic sensor of the present invention can suppress the angular error, the angle error is small even thickness variation and H int fluctuations at high temperatures of the intermediate layer having It can be seen that a magnetic sensor is obtained.
- FIG. 32 shows a specific example of element arrangement in the bridge circuit shown in FIG. Arrows X and Y in the figure indicate the side direction of the sensor chip on which the element is formed.
- FIG. 33 schematically shows the element arrangement of FIG. 32 together with the fixed layer magnetization direction (indicated by an arrow).
- Elements 311a and 311c having the same fixed layer magnetization direction, elements 311b and 311d (enclosed by dotted lines as an example),... are at a desired angle (for example, ⁇ 40 °) with respect to the fixed layer magnetization direction.
- a desired angle for example, ⁇ 40 °
- the elements 311c and 311b and the elements 313a and 313d are equivalent, so even if the elements 313a and 313d are replaced, the relationship between the longitudinal direction of the element and the fixed layer magnetization direction is changed as shown in FIG. Absent. Insulation between the bridges is obtained by interposing an insulating layer at the intersection of the wirings.
- 35 and 36 show another example of element arrangement. The example of FIGS. 35 and 36 differs from the example shown in FIG. 33 in the angle of the adjacent element, but the relationship between the longitudinal direction of the element and the fixed layer magnetization direction is the same.
- FIG. 37 shows a bridge circuit in which the element of FIG. 33 is rotated by 45 ° in the plane. By rotating each element 45 ° from FIG. 33, the arrangement of the elements can be made denser. In other words, by optimizing the relationship between the element longitudinal direction and the pinned layer magnetization direction, it is highly resistant to fluctuations in the characteristics of the SVGMR film, allows free element placement, reduces output distortion, and reduces angular errors. A magnetic sensor and a rotation angle detection device can be obtained. Also, in the configuration of FIG. 37, the direction of a part of the magnetization can be changed as shown in FIG. 39 and 40 show still another example.
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Abstract
Description
前記磁気センサは、4個の磁気抵抗効果素子を接続したブリッジ回路X及び4個の磁気抵抗効果素子を接続したブリッジ回路Yを有し、
前記磁気抵抗効果素子の各々は、一方向に固定された磁化方向を有する固定層と、磁化方向が外部磁界方向に揃うように可変な自由層と、前記固定層と前記自由層に挟まれた中間層とを有するスピンバルブ型巨大磁気抵抗効果膜を有し、
前記補正回路は、前記ブリッジ回路Xの出力電圧Vx及び前記ブリッジ回路Yの出力電圧Vyから差(Vx-Vy)及び和(Vx+Vy)を算出するとともに、両者の振幅を同じに揃え、
前記角度演算回路は、前記補正回路から出力された同じ振幅を有する(Vx-Vy)’信号及び(Vx+Vy)’信号から求めた(Vx-Vy)’/(Vx+Vy)’を逆正接演算することにより前記磁石回転子の回転角度を求めることを特徴とする。
前記磁気センサは、4個の磁気抵抗効果素子を接続したブリッジ回路X及び4個の磁気抵抗効果素子を接続したブリッジ回路Yを有し、
前記磁気抵抗効果素子の各々は、一方向に固定された磁化方向を有する固定層と、磁化方向が外部磁界方向に揃うように可変な自由層と、前記固定層と前記自由層に挟まれた中間層とを有するスピンバルブ型巨大磁気抵抗効果膜を有し、
前記オペアンプ回路は、前記ブリッジ回路Xの出力電圧Vx及び前記ブリッジ回路Yの出力電圧Vyから差(Vx-Vy)及び和(Vx+Vy)を算出し、
前記補正回路は前記オペアンプ回路から出力された(Vx-Vy)信号及び(Vx+Vy)信号の振幅を同じに揃え、
前記角度演算回路は、前記補正回路から出力された同じ振幅を有する(Vx-Vy)’信号及び(Vx+Vy)’信号から求めた(Vx-Vy)’/(Vx+Vy)’を逆正接演算することにより前記磁石回転子の回転角度を求めることを特徴とする。
図1は回転角度検出装置の一例を示す。この装置は、SVGMR素子をブリッジ接続してなる磁気センサ31と、磁気センサ31に対向する直径方向に2極着磁した円盤状永久磁石33と、永久磁石33を固定する冶具34と、冶具34と一体的な回転シャフト34bとを具備し、永久磁石33が回転すると漏洩磁界が変化する。図1において一点鎖線は回転中心軸線を示し、永久磁石33と磁気センサ32と間の矢印32は磁力線を示す。SVGMR素子の面内方向の磁界変化を磁気センサ31で検出する。図1に示す回転角検出装置の他の例は、磁気センサが31から31’に移動したものである。磁気センサ31’の基板面は永久磁石33の外周面と対向し、前記回転中心軸線と平行な中心軸線を有する。
図2はSVGMR膜の層構成の一例を概略的に示すが、各層の厚さの拡大倍率は必ずしも一定ではない。SVGMR膜は基板10上に順に形成された下地膜11、固定層12、中間層13、自由層14及び保護層15を有する。固定層12は下から順に反強磁性層121、第一の強磁性層122、反平行結合層123及び第二の強磁性層124を有し、自由層14は2層以上の強磁性層141、142を有する。固定層12は一方向に固定された磁化方向(一方向の磁気異方性)を有する。固定層磁化方向と、外部磁界により自由に回転する自由層14の磁化方向とがなす角度に応じて電気抵抗が変化する。
Etotal=Ekd+Ek+Eex+Ez・・・(1)
ただし、EkdはSVGMR素子の形状磁気異方性エネルギーであり、Ekは自由層の磁気異方性エネルギーであり、EexはSVGMR膜の層間交換結合エネルギーであり、EzはSVGMR膜のゼーマンエネルギーであり、それぞれ下記式(2)~(5) により表される。
Ekd=Kud sin2(θM-θdip)・・・(2)
Ek=Ku sin2(θM-θfree)・・・(3)
Eex=-Hint・MScos(θM-θfree)・・・(4)
Ez=-Happ・MScos(θapp-θM)・・・(5)
Kud=(Hkd・MS)/2・・・(6)
Ku=(Hk・MS)/2・・・(7)
式(8) の前半の項はGMR効果による抵抗変化を表し、後半の項はAMR効果による抵抗変化を表す。
本発明の回転角度検出装置に用いる信号処理回路には、(a) 補正回路と、角度演算回路とを具備する第一の信号処理回路と、(b) オペアンプ回路と、補正回路と、角度演算回路とを具備する第二の信号処理回路とがある。
第一及び第二の信号処理回路のいずれも、磁気センサの製造ばらつき等による角度誤差を低減することができる。例えば、ブリッジ回路Xの出力Vxとブリッジ回路Yの出力Vyとの位相差がπ/2ではなく、製造ばらつき等によりπ/2±Δとなることがある。図12は、試料3-4のブリッジ回路Xとブリッジ回路Yとの位相差π/2±Δにおいて、Δが0°の場合と1°の場合での角度誤差θerrとθapp(基準軸に対するHappの角度)との関係を示す。図12からΔにより角度誤差が増大することが分かる。
Vx=cosθapp ・・・(13)
Vy=cos (θapp-π/2+Δ) ・・・(14)
Vx-Vy=2 sin (π/4-Δ/2) sin (θapp-π/4+Δ/2) ・・・(15)
Vx+Vy=2 cos (π/4-Δ/2) cos (θapp-π/4+Δ/2) ・・・(16)
図14は位相ズレを打ち消す第一の信号処理回路40を示す。回転角度検出装置は、シャフトに固定した2極磁石33を有する回転子と、2極磁石33の近傍に配置された磁気センサ31とを有する。信号処理回路40は、磁気センサ31内のブリッジ回路X,Yの出力電圧Vx,Vyを入力するオペアンプ41a、41bと、オペアンプ41a、41bの出力を入力するA-D変換補正回路42と、A-D変換補正回路42の出力を入力する角度演算回路43とを有する。オペアンプ41aは出力電圧Vx,Vy からVx-Vyを演算し、オペアンプ41bは出力電圧Vx,Vy からVx+Vyを演算する。A-D変換補正回路42は、オペアンプ41a,41bの(Vx-Vy)信号及び(Vx+Vy)信号を入力して、アナログ-デジタル変換するとともに、それらの振幅が同じとなるように補正し、振幅が同じ(Vx-Vy)’信号及び(Vx+Vy)’信号を出力する。角度演算回路43は、補正回路42から出力された(Vx-Vy)’信号及び(Vx+Vy)’信号を入力し、(Vx-Vy)’/(Vx+Vy)’の逆正接演算を行って角度θを求める。
図15は位相ズレを打ち消す第二の信号処理回路40’を示す。回転角度検出装置は図14に示すものと同じである。信号処理回路40’は、磁気センサ31内のブリッジ回路X,Yから出力電圧Vx,Vyを入力し、アナログ-デジタル変換した後、(Vx-Vy)及び(Vx+Vy)を演算するとともにそれらの振幅補正をするA-D変換補正回路42’と、A-D変換補正回路42’の出力(Vx-Vy)’,(Vx+Vy)’を入力して、(Vx-Vy)’/(Vx+Vy)’の逆正接演算により角度θを求める角度演算回路43とを有する。第二の信号処理回路40’では、第一の信号処理回路40におけるオペアンプ41a,41bとA-D変換補正回路の機能をA-D変換補正回路42’で行う。
例1
図16は、SVGMR素子のブリッジ回路X及びブリッジ回路Yを有する磁気センサの一例を示す。図示の素子配置は後述する表1の試料1-3に相当する。ブリッジ回路Xでは、基板上に4個の矩形状SVGMR素子201a~201dが形成されており、素子201b及び201cは電源端子Vccに接続されており、素子201a及び201dはグランド端子GNDに接続されており、素子201a及び201bは一方の出力端子Vx1に接続されており、素子201c及び201dは他方の出力端子Vx2に接続されている。矢印で示す固定層磁化方向と平行な軸線202に対して、素子201a~201dの長手方向は角度θdip-R1~θdip-R4だけ傾斜している。ブリッジ回路Yでは、基板上に4個の矩形状SVGMR素子203a~203dが形成されており、それぞれブリッジ回路Xの対応する素子201a~201dに対して直交している。軸線202と直交する軸線204に対して各素子の固定層磁化方向は平行であるが、長手方向は角度θdip-R5~θdip-R8だけ傾斜している。図16に示す磁気センサでは、固定層磁化方向が同じ素子の長手方向は平行である。各素子201a~201d、203a~203dのθdip-R1~θdip-R4及びθdip-R5~θdip-R8は以下の関係を満たす。
素子201aのθdip-R1=素子201cのθdip-R3
素子201bのθdip-R2=素子201dのθdip-R4
θdip-R1=-θdip-R2
素子203aのθdip-R5=素子203cのθdip-R7
素子203bのθdip-R6=素子203dのθdip-R8
θdip-R5=-θdip-R6
SVGMR素子の抵抗を大きくして磁気センサの消費電力を抑えるために、素子の長手方向寸法を数十~100μm程度にすることがある。このように素子を長くするとSVGMR膜の自由層の形状異方性が大きくなり、自由層のAMR効果が無視できない。そこで、例1と同じ素子配置の磁気センサにおいてθdipを表3(素子の反時計方向角度を「+」で表し、括弧内にθdip-180°の値を示す。)に示す通り変化させて、AMR効果を加味した場合及び加味しない場合のΔθerrをシミュレーションにより求めた。結果を図25に示す。式(8) において、SVGMR膜に対する自由層の膜厚比及びNiFe膜の比抵抗から、AMRに寄与する抵抗値を7500Ωと仮定し、かつAMR比を0.3%と仮定してdR’を22.5Ωと見積もった。試料2-5は特表2003-502876号及び特開2005-024287号に記載の素子配置である。
素子211aのθdip-R1=素子211dのθdip-R4
素子211bのθdip-R2=素子211cのθdip-R3
θdip-R1=-θdip-R2
素子213aのθdip-R5=素子213dのθdip-R8
素子213bのθdip-R6=素子213cのθdip-R7
θdip-R5=-θdip-R6
SVGMR膜において最も変動しやすい磁気特性はHint(中間層を介した固定層と自由層との間に働く磁界)である。Hintは、中間層の膜厚変動、中間層の表面粗さによるいわゆる「オレンジピール効果」、動作温度や環境温度等の温度に応じて変動しやすい。そこで最適な素子配置の条件(試料3-4)でHintとΔθerrとの関係を求めるために、図26に示す磁気センサにおいて下記条件で素子213aのHint(Hint-R5)を-0.8 kA/mから+0.8 kA/mまで変化させたときのΔθerrを、Hint-R1が0 kA/m,0.08 kA/m,0.16 kA/m,0.40 kA/m,及び0.80 kA/mの場合についてそれぞれシミュレーションにより計算した。結果を図31に示す。
素子211aのHint-R1=素子211dのHint-R4
素子211bのHint-R2=素子211cのHint-R3
Hint-R1=-Hint-R2
素子213aのHint-R5=素子213dのHint-R8
素子213bのHint-R6=素子213cのHint-R7
Hint-R5=-Hint-R6
図32は、図26に示すブリッジ回路における素子配置の具体的な一例を示す。図中矢印X及びYは素子を形成したセンサチップの辺方向を示す。図33は図32の素子配置を固定層磁化方向(矢印で示す)とともに概略的に示す。固定層磁化方向が同じ素子311aと311c、素子311bと311d(例として点線で囲まれている)、・・・等は固定層磁化方向に対して所望の角度(例えば±40°)にある。しかし、素子311aと311c、及び素子311bと311dはそれぞれ平行でないので、AMR効果をキャンセルする。
Claims (4)
- 磁石回転子と、前記磁石回転子からの磁束の方向を検出する磁気センサと、補正回路と、角度演算回路とを具備する回転角度検出装置であって、
前記磁気センサは、4個の磁気抵抗効果素子を接続したブリッジ回路X及び4個の磁気抵抗効果素子を接続したブリッジ回路Yを有し、
前記磁気抵抗効果素子の各々は、一方向に固定された磁化方向を有する固定層と、磁化方向が外部磁界方向に揃うように可変な自由層と、前記固定層と前記自由層に挟まれた中間層とを有するスピンバルブ型巨大磁気抵抗効果膜を有し、
前記補正回路は、前記ブリッジ回路Xの出力電圧Vx及び前記ブリッジ回路Yの出力電圧Vyから差(Vx-Vy)及び和(Vx+Vy)を算出するとともに、両者の振幅を同じに揃え、
前記角度演算回路は、前記補正回路から出力された同じ振幅を有する(Vx-Vy)’信号及び(Vx+Vy)’信号から求めた(Vx-Vy)’/(Vx+Vy)’を逆正接演算することにより前記磁石回転子の回転角度を求めることを特徴とする回転角度検出装置。 - 磁石回転子と、前記磁石回転子からの磁束の方向を検出する磁気センサと、オペアンプ回路と、補正回路と、角度演算回路とを具備する回転角度検出装置であって、
前記磁気センサは、4個の磁気抵抗効果素子を接続したブリッジ回路X及び4個の磁気抵抗効果素子を接続したブリッジ回路Yを有し、
前記磁気抵抗効果素子の各々は、一方向に固定された磁化方向を有する固定層と、磁化方向が外部磁界方向に揃うように可変な自由層と、前記固定層と前記自由層に挟まれた中間層とを有するスピンバルブ型巨大磁気抵抗効果膜を有し、
前記オペアンプ回路は、前記ブリッジ回路Xの出力電圧Vx及び前記ブリッジ回路Yの出力電圧Vyから差(Vx-Vy)及び和(Vx+Vy)を算出し、
前記補正回路は前記オペアンプ回路から出力された(Vx-Vy)信号及び(Vx+Vy)信号の振幅を同じに揃え、
前記角度演算回路は、前記補正回路から出力された同じ振幅を有する(Vx-Vy)’信号及び(Vx+Vy)’信号から求めた(Vx-Vy)’/(Vx+Vy)’を逆正接演算することにより前記磁石回転子の回転角度を求めることを特徴とする回転角度検出装置。 - 請求項1又は2に記載の回転角度検出装置において、前記磁気抵抗効果素子の少なくとも一つの長手方向がその固定層磁化方向に対して36°≦θ<45°の条件を満たす鋭角θだけ傾いていることを特徴とする回転角度検出装置。
- 請求項1~3のいずれかに記載の回転角度検出装置において、前記ブリッジ回路X及び前記ブリッジ回路Yの各々における4個の磁気抵抗効果素子のうち、2個の磁気抵抗効果素子が固定層磁化方向に対して鋭角θだけ傾き、残りの2個が鋭角-θだけ傾いていることを特徴とする回転角度検出装置。
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US9529060B2 (en) | 2014-01-09 | 2016-12-27 | Allegro Microsystems, Llc | Magnetoresistance element with improved response to magnetic fields |
US9804234B2 (en) | 2014-01-09 | 2017-10-31 | Allegro Microsystems, Llc | Magnetoresistance element with an improved seed layer to promote an improved response to magnetic fields |
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US9812637B2 (en) | 2015-06-05 | 2017-11-07 | Allegro Microsystems, Llc | Spin valve magnetoresistance element with improved response to magnetic fields |
WO2018173590A1 (ja) * | 2017-03-23 | 2018-09-27 | 日本電産株式会社 | 磁気センサユニット及びそれを用いた磁界方向検出方法 |
US10620279B2 (en) | 2017-05-19 | 2020-04-14 | Allegro Microsystems, Llc | Magnetoresistance element with increased operational range |
US11002807B2 (en) | 2017-05-19 | 2021-05-11 | Allegro Microsystems, Llc | Magnetoresistance element with increased operational range |
US11022661B2 (en) | 2017-05-19 | 2021-06-01 | Allegro Microsystems, Llc | Magnetoresistance element with increased operational range |
US11719771B1 (en) | 2022-06-02 | 2023-08-08 | Allegro Microsystems, Llc | Magnetoresistive sensor having seed layer hysteresis suppression |
Also Published As
Publication number | Publication date |
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US8093886B2 (en) | 2012-01-10 |
JP5387583B2 (ja) | 2014-01-15 |
EP2416125A4 (en) | 2013-10-23 |
EP2416125B1 (en) | 2015-01-07 |
CN102016513A (zh) | 2011-04-13 |
EP2416125A1 (en) | 2012-02-08 |
JPWO2010113820A1 (ja) | 2012-10-11 |
CN102016513B (zh) | 2013-04-10 |
US20110037459A1 (en) | 2011-02-17 |
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