WO2018090636A1 - 一种宽磁场范围测量方法及装置 - Google Patents

一种宽磁场范围测量方法及装置 Download PDF

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WO2018090636A1
WO2018090636A1 PCT/CN2017/090548 CN2017090548W WO2018090636A1 WO 2018090636 A1 WO2018090636 A1 WO 2018090636A1 CN 2017090548 W CN2017090548 W CN 2017090548W WO 2018090636 A1 WO2018090636 A1 WO 2018090636A1
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magnetic field
magnetoresistive
magnetization direction
resistors
reference layer
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French (fr)
Inventor
何金良
欧阳勇
胡军
王善祥
赵根
王中旭
曾嵘
庄池杰
张波
余占清
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Tsinghua University
Sichuan Energy Internet Research Institute EIRI Tsinghua University
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Tsinghua University
Sichuan Energy Internet Research Institute EIRI Tsinghua University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/09—Magnetoresistive devices
    • G01R33/093—Magnetoresistive devices using multilayer structures, e.g. giant magnetoresistance sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/0023—Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration
    • G01R33/0029—Treating the measured signals, e.g. removing offset or noise
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/0094—Sensor arrays
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/09—Magnetoresistive devices
    • G01R33/098—Magnetoresistive devices comprising tunnel junctions, e.g. tunnel magnetoresistance sensors

Definitions

  • the invention relates to the field of magnetic field measurement technology, in particular to a method for measuring magnetic field strength in a small range magnetic field, a medium range and a very large range.
  • H AF is the anisotropy field of the free layer of the reluctance resistance
  • Oe.Oe is a unit of magnetic field strength - Oersted with good linearity and good measurement accuracy.
  • the existing small magnetic field measurement method considers that the sensitivity is the highest in the hard axis direction of the magnetoresistive resistor (that is, the angle between the magnetic field direction and the easy axis direction is 90°), and the magnitude and direction of the magnetic field are calculated according to the resistance value of the magnetoresistive resistor. Calculated as the direction of maximum sensitivity.
  • the existing magnetoresistive resistance measurement model is difficult to measure the magnetic field in a large range (magnetic field strength is about 4 ⁇ 6H AF ) because: 1) the sensing curve of the magnetoresistive resistance is linear in the medium range Saturated, severely nonlinear, need to establish a nonlinear model for calculation; 2) the reference layer of the magnetoresistive resistor will undergo significant rotation, the influence of the reference layer must be considered; 3) the direction of the magnetoresistive magnetic domain may irreversibly flip, the resistance value will jump Change, forming different sensing curves for the two forks.
  • the existing measurement methods can not adapt to the measurement of the large magnetic field range (the magnetic field range is about 1 mOe to 2.5 kOe), and a new method suitable for large magnetic field measurement needs to be proposed.
  • the invention provides a method for measuring a large magnetic field, comprising: a medium magnetic field measuring step and a maximum magnetic field measuring step; and further comprising:
  • Step 1 Place the four orthogonally configured reluctance resistors into an external magnetic field and obtain the resistance values of the respective reluctance resistors; the first reluctance resistor and the third reluctance resistor are in a straight line, and the second reluctance resistor And the fourth magnetoresistive resistor is located on another straight line, the straight line being perpendicular to the other straight line;
  • Step 2 If the resistance value of the four magnetoresistive resistors is less than the set value when the magnetic field is 0, the small magnetic field measurement step is used to measure the external magnetic field; if four magnetic resistances are detected; When the resistance of the resistor is reduced, the maximum magnetic field measurement step is used to measure the applied magnetic field;
  • the resistance values of the four magnetoresistive resistors do not satisfy the above two judgment conditions, the resistance values of two mutually orthogonal reluctance resistors are taken into the medium and large magnetic field measurement steps, and if the calculation process converges, the applied magnetic field is judged.
  • the calculation result is the magnetic field strength and direction of the medium and large magnetic field; if the calculation process does not converge, the resistance of the four magnetoresistive resistors is taken into the maximum magnetic field measurement step, and the applied magnetic field is judged to be the maximum magnetic field.
  • the calculation result is the magnetic field strength and direction of the maximum magnetic field;
  • the medium and large magnetic field measuring step further comprises:
  • Step M1 Obtaining the resistance values of two mutually orthogonal reluctance resistors in the applied magnetic field, and taking the initial reference layer magnetization directions of the two reluctance resistors as a given reference layer magnetization direction when there is no magnetic field
  • Step M2 calculating the angle between the magnetization direction of the free layer of the two magnetoresistive resistors and the magnetization direction of the reference layer according to the resistance values of the two magnetoresistive resistors;
  • Step M3 respectively according to the magnetization direction of a given reference layer of the two magnetoresistive resistors And the angle between the magnetization direction of the free layer of the two magnetoresistive resistors and the magnetization direction of the reference layer to calculate the free layer magnetization direction of the two magnetoresistive resistors;
  • Step M4 Solving the amplitude and direction of the magnetic field of the applied magnetic field according to the magnetization direction of the reference layer of the two reluctance resistors and the free layer magnetization direction of the two reluctance resistors;
  • Step M5 comparing the amplitude and direction of the magnetic field of the applied magnetic field calculated in this calculation with the previous calculation result, if the difference between the two results is greater than the set threshold, the magnetic field amplitude of the applied magnetic field according to the current calculation is obtained. And direction update the reference layer magnetization direction of the two magnetoresistive resistors and use it as the new given reference layer magnetization direction And performing step M2 to step M5 again until the difference between the two results is less than the set value;
  • Step N1 calculating an angle between a magnetization direction of the free layer of each magnetoresistive resistor and a magnetization direction of the reference layer according to the resistance values of the four magnetoresistive resistors;
  • Step N2 calculating the magnetic field intensity H 1 of the applied magnetic field according to the angle between the magnetization direction of the free layer of the first magnetoresistive resistor and the magnetization direction of the reference layer and the angle between the magnetization direction of the free layer of the third magnetoresistive resistor and the magnetization direction of the reference layer The direction ⁇ 1 ;
  • the magnetic field strength H 2 of the applied magnetic field is calculated according to the angle between the magnetization direction of the free layer of the second magnetoresistive resistor and the magnetization direction of the reference layer and the angle between the magnetization direction of the free layer of the fourth magnetoresistive resistor and the magnetization direction of the reference layer And direction ⁇ 2 ;
  • Step N3 Determine the final magnetic field strength H 0 of the applied magnetic field according to the magnetic field strength H 1 and the magnetic field strength H 2 , and determine the final direction ⁇ of the applied magnetic field according to the direction ⁇ 2 and the direction ⁇ 1 .
  • Step S1 collecting resistance values R 1 and R 2 of two mutually orthogonal magnetoresistive resistors in the magnetic field to be tested;
  • R is the resistance of the magnetoresistive resistance placed in the magnetic field to be measured
  • H 0 is the magnetic field strength of the magnetic field to be measured
  • ⁇ is the magnetic field direction of the magnetic field to be measured
  • H AF and H AR are the anisotropy field amplitudes of the magnetoresistive resistance free layer and the anisotropy field amplitudes of the reference layer, respectively;
  • h BF H BF /H AF , H BF and ⁇ BF are respectively magnetic The amplitude and direction of the internal bias magnetic field of the resistive free layer;
  • h BR H BR /H AR, H BR and ⁇ BR are the amplitude and direction of the internal bias magnetic field of the magnetoresistive resistor reference layer;
  • Step S3 Solving the binary equations in step 2, and obtaining the magnetic field strength H 0 and the direction ⁇ of the magnetic field to be measured.
  • the maximum magnetic field measuring step further includes a step N4 of optimizing the magnetic field strength H 0 according to the direction ⁇ .
  • the invention provides a large magnetic field measuring device, comprising: a small magnetic field measuring module, a medium and large magnetic field measuring module and a maximum magnetic field measuring module; and the method further comprises:
  • the magnetoresistive resistance value obtaining module is configured to obtain resistance values of four orthogonally configured magnetoresistive resistors in the external magnetic field; the first magnetoresistive resistor and the third magnetoresistive resistor are in a straight line, and the second magnetoresistive resistor and the first The four magnetoresistive resistor is located on another straight line, the one straight line being perpendicular to the other straight line;
  • the magnetic field calculation module is configured to: if the resistance value of the four magnetoresistive resistors is detected to be smaller than the set value when the magnetic field is 0, the small magnetic field measurement module is called to measure the external magnetic field; When the resistance of the four magnetoresistive resistors becomes smaller, the maximum magnetic field measurement module is called to measure the external magnetic field;
  • the resistance values of the four magnetoresistive resistors do not satisfy the above two judgment conditions, the resistance values of two mutually orthogonal reluctance resistors are brought into the calculation of the medium and large magnetic field measurement module, and if the calculation process converges, the applied magnetic field is judged.
  • the calculation result is the magnetic field strength and direction of the medium and large magnetic field; if the calculation process does not converge, the resistance value of the four magnetoresistive resistors is taken into the maximum magnetic field measurement module, and the applied magnetic field is judged to be the maximum magnetic field.
  • the calculation result is the magnetic field strength and direction of the maximum magnetic field;
  • the medium and large magnetic field measurement module further comprises:
  • the initialization sub-module is configured to obtain the resistance values of two mutually orthogonal reluctance resistors in the applied magnetic field, and simultaneously use the initial reference layer magnetization direction of the two reluctance resistors as a given reference layer magnetization direction when there is no magnetic field
  • the free layer and the reference layer angle calculation sub-module are respectively configured to calculate an angle between a free layer magnetization direction of the two magnetoresistive resistors and a magnetization direction of the reference layer according to the resistance values of the two magnetoresistive resistors;
  • Free layer magnetization direction calculation sub-module for respectively determining the reference layer magnetization direction according to two reluctance resistors And the angle between the magnetization direction of the free layer of the two magnetoresistive resistors and the magnetization direction of the reference layer to calculate the free layer magnetization direction of the two magnetoresistive resistors;
  • the external magnetic field calculation sub-module solves the amplitude and direction of the magnetic field of the applied magnetic field according to the magnetization direction of the reference layer of the two reluctance resistors and the free layer magnetization direction of the two reluctance resistors;
  • the precision judgment sub-module is configured to compare the amplitude and direction of the magnetic field of the applied magnetic field calculated by the current calculation with the previous calculation result, and if the difference between the two results is greater than the set threshold, the applied magnetic field is calculated according to the current calculation.
  • the magnitude and direction of the magnetic field update the reference layer magnetization direction of the two magnetoresistive resistors and use it as the new given reference layer magnetization direction
  • a pre-calculation sub-module for the magnetic field strength and direction of the applied magnetic field for the angle between the magnetization direction of the free layer of the first magnetoresistive resistor and the magnetization direction of the reference layer, and the magnetization direction of the free layer of the third reluctance resistor and the magnetization direction of the reference layer
  • the angle between the magnetic field strength H 2 and the direction ⁇ 2 of the applied magnetic field is calculated;
  • the magnetic field strength and direction determining sub-module of the applied magnetic field is used for determining the final magnetic field strength H 0 of the applied magnetic field according to the magnetic field strength H 1 and the magnetic field strength H 2 , and determining the final direction ⁇ of the applied magnetic field according to the direction ⁇ 2 and the direction ⁇ 1 .
  • a magnetoresistive resistance value obtaining sub-module for obtaining resistance values R 1 and R 2 of two mutually orthogonal magnetoresistive resistors in a magnetic field to be tested;
  • R is the resistance of the magnetoresistive resistance placed in the magnetic field to be measured
  • H 0 is the magnetic field strength of the magnetic field to be measured
  • ⁇ is the magnetic field direction of the magnetic field to be measured
  • H AF and H AR are the anisotropy field amplitudes of the magnetoresistive resistance free layer and the anisotropy field amplitudes of the reference layer, respectively;
  • h BF H BF /H AF , H BF and ⁇ BF are respectively magnetic The amplitude and direction of the internal bias magnetic field of the resistive free layer;
  • h BR H BR /H AR, H BR and ⁇ BR are the amplitude and direction of the internal bias magnetic field of the magnetoresistive resistor reference layer;
  • the free layer and the reference layer angle calculation sub-module, the free layer magnetization direction calculation sub-module, the external magnetic field calculation sub-module, and the accuracy judgment sub-module are repeatedly executed, the difference between the calculation result and the previous calculation result is repeated. If the value is still not less than the set value, it is considered that the calculation process of the medium and large magnetic field measurement module does not converge.
  • the maximum magnetic field measurement module further includes a magnetic field strength optimization sub-module for optimizing the magnetic field strength H 0 according to the direction ⁇ .
  • the large magnetic field measurement method provided by the invention realizes accurate measurement of a large magnetic field, and the measurement range is expanded. From 2mOe to 2500Oe, the dynamic range is up to 6 orders of magnitude. In particular, the measurable maximum magnetic field extends from the traditional tens of Oersted to thousands of Oersted, extending about 40 times.
  • Figure 1 is a distribution diagram of the reluctance resistance in an applied magnetic field.
  • Figure 3 is a tunneling reluctance single domain model.
  • Figure 4 is a simulation of the sensitivity of the contribution of the free layer of the tunneling magnetoresistive resistor to the reference layer as a function of angle in a small magnetic field environment.
  • Figure 5 is a flow chart of the measurement steps of the medium and large magnetic fields.
  • Figure 6 is a schematic diagram of a normalized asteroid curve for single domain behavior of magnetoresistive resistors.
  • Figure 7 shows the vector diagram of the maximum magnetic field measurement.
  • resistors four orthogonally arranged reluctance resistors (I are hereinafter referred to as resistors) are placed in an external magnetic field, and the arrangement is as shown in FIG.
  • the resistor R1 and the resistor R3 are located on a straight line, and the resistor R2 and the resistor R4 are located on another straight line, and the two straight lines are orthogonal.
  • a method for measuring a large magnetic field includes:
  • Step 1 Obtain the resistance values of the aforementioned four magnetoresistive resistors.
  • Step 2 If the resistance value of the four magnetoresistive resistors is less than the set value when the magnetic field is 0, the set value is adjustable according to different technical precision requirements, such as 2% to 5 %, if the external magnetic field is small, the small magnetic field measurement module is called to measure the external magnetic field; if the resistance of the four magnetoresistive resistors is detected to be small, the maximum magnetic field measurement module is directly called to measure the external magnetic field;
  • the resistance values of the four magnetoresistive resistors do not satisfy the above two judgment conditions, the resistance values of two mutually orthogonal reluctance resistors, such as R1 and R2 or R3 or R4, are brought into the medium and large magnetic field measurement steps.
  • the external magnetic field is determined to be a medium-large magnetic field and the calculation result is the magnetic field strength and direction of the medium-large magnetic field; if the calculation process does not converge, the resistance values of the four magnetoresistive resistors are brought into the maximum magnetic field measurement step. And judge that the applied magnetic field is a maximum magnetic field, and the calculation result is the magnetic field strength and direction of the maximum magnetic field.
  • the following describes the small magnetic field measurement steps, the medium and large magnetic field measurement steps, and the maximum magnetic field measurement steps.
  • the resistances R 1 , R 2 of the two orthogonal magnetoresistive resistors in the small magnetic field to be measured are measured.
  • R 3 and R 4 calculations it is also possible to obtain R 3 and R 4 calculations. This embodiment performs calculations with resistance values R 1 and R 2 .
  • R is the resistance of the magnetoresistive resistance placed in the magnetic field to be measured
  • H 0 is the magnetic field strength of the magnetic field to be measured
  • ⁇ is the magnetic field direction of the magnetic field to be measured
  • H AF and H AR are the anisotropy field amplitudes of the magnetoresistive resistance free layer and the anisotropy field amplitudes of the reference layer, respectively;
  • h BF H BF /H AF , H BF and ⁇ BF are respectively magnetic The internal bias magnetic field amplitude and direction of the resistive free layer;
  • h BR H BR /H AR, H BR and ⁇ BR are the internal bias magnetic field amplitude and direction of the magnetoresistive resistor reference layer, respectively.
  • R 1 k m1 cos( ⁇ - ⁇ 01 )H 0 +R 01 ;
  • R 2 k m2 cos( ⁇ - ⁇ 02 - ⁇ ')H 0 +R 02 ;
  • the resistance of the first magnetoresistive resistor when R 01 is zero magnetic field can be tested.
  • the saturation magnetization direction of the free layer and the saturation magnetization direction of the reference layer when the first magnetoresistive resistor is placed in a zero magnetic field Can be measured at zero magnetic field.
  • H AF1 and H AR1 are the anisotropy field amplitudes of the first magnetoresistive resistor free layer and the anisotropy field amplitudes of the reference layer;
  • h BF1 H BF1 /H AF1 , H BF1 , ⁇ BF1 respectively The amplitude and direction of the internal bias magnetic field of the free layer of the first magnetoresistive resistor;
  • h BR1 H BR1 /H AR1 , H BR1 , ⁇ BR1 are the amplitudes and directions of the internal bias magnetic field of the first magnetoresistive resistor reference layer, respectively
  • the method of the invention is applicable to various types of magnetoresistive resistors, including tunneling magnetoresistance resistors, giant magnetoresistance resistors, and spin valve structure magnetoresistive resistors.
  • the tunneling magnetoresistive resistor is taken as an example to illustrate the derivation process of the above method, so that those skilled in the art can The staff better understand the invention.
  • the tunneling magnetoresistive resistance includes two components: a free layer component and a reference layer component.
  • the maximum sensitivity direction of each component is perpendicular to its initial magnetization direction.
  • R avg (R max +R min )/2, which is the average resistance
  • ⁇ max (R max -R min )/R avg , which is the maximum magnetoresistance change rate.
  • the sensitivity amplitude is:
  • the sensitivity direction is:
  • the medium and large magnetic field measurement steps include:
  • the magnetoresistance resistances of two different easy-axis directions are measured.
  • the resistances of the resistors R 1 and R 2 that are orthogonal to each other are used, and the two resistors are Initial reference layer magnetization direction as a given direction in a magnetic field
  • the typical core structure of magnetoresistance includes antiferromagnetic layer (pinning layer) / ferromagnetic layer (pinned layer) / non-magnetic metal / ferromagnetic layer (reference layer) / barrier layer / ferromagnetic layer (free layer), the current is perpendicular to the membrane surface.
  • the reference layer and the pinned layer are induced to form a synthetic antiferromagnetic structure through a very thin non-magnetic metal, so that the magnetization directions of the reference layer and the pinned layer are more stable and are not easily damaged by external strong magnetic fields.
  • the magnetization direction of the free layer changes as the external magnetic field changes.
  • the reluctance resistance is most easily magnetized along an axis or direction, it is called an easy axis, and vice versa.
  • the resistance of the magnetoresistive resistor can vary with the applied magnetic field, so measuring the resistance can measure the applied magnetic field.
  • Two magnetoresistive resistors with different easy axis directions are placed in an external magnetic field, and the resistance values of the two resistors can be obtained by a full bridge or other resistance measuring circuit.
  • R 1min is the minimum value of the first reluctance resistance
  • R 1max is the maximum value of the first reluctance resistance
  • R 2min is the minimum value of the second reluctance resistance
  • R 2max is the maximum value of the second reluctance resistance
  • the value of the magnetoresistance resistance is the smallest, which is R min .
  • the resistance value is the largest, which is R max .
  • R 1min and R 1max are the minimum and maximum values of the first reluctance resistance
  • R 2min and R 2max are the minimum and maximum values of the second reluctance resistance, which can be obtained by respectively calibrating two reluctance resistors.
  • S 1 and S 2 respectively indicate that the free layer magnetic domain is in the range of the easy axis positive direction (- ⁇ /2 to ⁇ /2) or the easy axis negative direction range ( ⁇ /2 to 3 ⁇ /2) in Fig. 6 .
  • the state of the free layer magnetic domain is unique for a particular magnetoresistive resistor.
  • the tunneling magnetoresistive resistor when the internal easy axis offset magnetic field of the tunneling magnetoresistive resistor free layer is larger than the anisotropy field, according to the arrangement of the four magnetoresistive resistors in the present invention, it is ensured that at least The free layer magnetic domain with two mutually orthogonal reluctance resistors is in the S1 state, and the two resistances with known states are selected to calculate the large magnetic field, and the free layer magnetization directions of the two can be determined.
  • a tunneling magnetoresistive resistor process in which an internal easy axis bias magnetic field is larger than an anisotropy field is known.
  • the four magnetoresistive resistors in this embodiment are the same, and therefore their inherent parameters are considered to be the same. In the calculation, the inherent parameters of any one of the magnetoresistance resistors can be selected.
  • the steps for updating the orientation direction magnetization direction angle are:
  • the above-mentioned quadruple equation has four solutions, when the tunneling reluctance is in a stable equilibrium state, There is only one solution.
  • the solution depends on three conditions:
  • x 1 is a real number and
  • the following formula can be solved by computer numerical method to obtain the reference layer magnetization direction angle of the magnetoresistive resistor, that is, the angle that the technician thinks may be brought into the following formula to judge whether the result is close to 0, and if so, the band is considered
  • the angle of entry is Solution: h X , h Y are the magnetic fields of the applied magnetic field in the direction of the easy-to-axis and the hard axis of the magnetoresistive resistor, respectively.
  • the above formula is a general expression for calculating the angle of magnetization in the reference layer for the tunneling magnetoresistive single domain model.
  • the above formula can be evolved as:
  • the former embodiment calculates the formula of the magnetization direction of the reference layer.
  • problems with accuracy, time, and global convergence using computer numerical methods Therefore, it is recommended to use the previous embodiment to calculate the magnetization direction of the reluctance resistance reference layer.
  • the reference layer magnetization direction will gradually converge to the real direction, and the calculated applied magnetic field also converges to the real applied magnetic field.
  • the convergence of the iterative algorithm depends on whether it converges when calculating the magnetization direction of the reference layer.
  • the iteration is set a number of times, the difference between the calculation result and the previous calculation result is still not small. Then the calculation process can not be converged, and the current applied magnetic field is a maximum magnetic field.
  • the number of times set is set according to different reluctance resistances and calculation accuracy requirements, and the number of times set in this embodiment is 20 times.
  • the maximum magnetic field measurement distribution of the four magnetoresistive resistors is as shown in Fig. 7.
  • the four resistors are sequentially rotated by 90° orthogonally.
  • H ⁇ is the amplitude and direction of the applied magnetic field
  • FL is the combined direction of the magnetization directions of the free layers of the four resistors, which can be approximated to be the same as the direction of the applied magnetic field
  • four vectors H BR represent the reference of the four magnetoresistance resistors.
  • the amplitude and direction of the internal bias field of the layer are the same in the present embodiment.
  • the internal bias field of the reference layer is considered to be the same, and the reference layer of the adjacent two magnetoresistive resistors is internally biased.
  • the field direction is orthogonal; RL 1, 2, 3, and 4 are respectively represented as reference layer magnetization directions of four resistors, which are consistent with the combined magnetic field and the combined direction of the internal bias field of the respective reference layer; The angle between the magnetization direction of the four resistance free layers and the magnetization direction of the reference layer.
  • the magnitude and direction of the applied magnetic field can be calculated from two of the above equations.
  • only two resistors cannot calculate the magnetic field of the entire two-dimensional plane.
  • the applied magnetic field is mirror-symmetric when the temperature ranges from 0° to 180° and 180° to 360°. Use the other two resistors to determine the range of the applied magnetic field, and then select the appropriate two resistors for calculation.
  • resistor R1 and resistor R3 as a group, it can be calculated:
  • H 1 and ⁇ 1 are the magnitude and direction of the applied magnetic field calculated by R 1 and R 3 , respectively.
  • resistor R2 and resistor R4 as another group, it can be calculated:
  • H 2 and ⁇ 2 are the magnitude and direction of the applied magnetic field calculated by R2 and R4, respectively.
  • the magnitude and direction of the applied magnetic field can be obtained as:
  • step (2) of the medium magnetic field measurement step the calculation process of the angle between the magnetization direction of the free layer of each magnetoresistive resistor and the magnetization direction of the reference layer.
  • the relationship between the correction coefficients k and b and the direction of the measured magnetic field is:
  • correction coefficients k and b are different for different reluctance resistances, and it is necessary to perform test test calibration for a specific reluctance resistance.
  • the specific method is to compare the H 0 calculated in the present invention with the real magnetic field (the result of the instrument with higher precision), and then obtain the numerical relationship between H 0 and the real magnetic field by numerical fitting.
  • the present invention also provides a software system corresponding to the steps of the above method.
  • the invention is not limited to the specific embodiments described above.
  • the invention extends to any new feature or any new combination disclosed in this specification, as well as any novel method or process steps or any new combination disclosed.

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Abstract

一种宽磁场范围测量方法及装置，涉及磁场测量技术领域，尤其是一种针对中大范围及极大范围的磁场强度的测量方法。该方法包括：中大磁场测量步骤及极大磁场测量步骤；另外还包括：步骤1：将四个正交配置的磁阻电阻放置到外加磁场中，并获取各个磁阻电阻的阻值；步骤2：将其中两个相互正交的磁阻电阻的阻值带入中大磁场测量步骤计算，若计算过程收敛则判断外加磁场为中大磁场且计算结果为中大磁场的磁场强度及方向；若计算过程不收敛则将四个磁阻电阻的阻值带入极大磁场测量步骤计算，且判断外加磁场为极大磁场，计算结果为极大磁场的磁场强度及方向。

Description

一种宽磁场范围测量方法及装置 技术领域
本发明涉及磁场测量技术领域，尤其是一种针对小范围磁场、中大范围及极大范围的磁场强度的测量方法。
背景技术
磁阻电阻在待测磁场较小时(磁场强度小于0.1HAF，HAF为磁阻电阻的自由层的各向异性场，不同的磁阻电阻其HAF是不同的，一般说来为几十Oe。Oe为磁场强度单位——奥斯特)具有良好的线性度，测量精度较好。
现有的小磁场测量方法认为在磁阻电阻的难轴方向上灵敏度最高(即磁场方向与易轴方向夹角为90°)，根据磁阻电阻的阻值计算磁场大小及方向时以该方向作为最大灵敏度方向进行计算。
然而我们在研究中发现磁阻电阻的最大灵敏度方向与磁场的夹角并非90°，而是会偏移一定角度。因此，现有的计算模型将不能更加精准的测量计算小磁场。需要基于我们的研究发现提供一种新的小磁场测量方法。
另外，现有的磁阻电阻测量模型难以对中大范围(磁场强度约为4～6HAF)的磁场进行测量，这是因为：1)磁阻电阻的传感曲线在中大范围由线性趋向饱和，严重非线性，需要建立非线性模型进行计算；2)磁阻电阻的参考层将发生显著旋转，必须考虑参考层的影响；3)磁阻磁畴方向可能发生不可逆翻转，电阻值会跳变，形成两根分叉的不同传感曲线。
当外界磁场极大时，磁阻参考层磁畴发生显著旋转，磁阻电阻进入饱和区。
可见现有的测量方法完全不能适应大磁场范围(磁场范围约为1mOe～2.5kOe)的测量，需要提出一种新的，适用于大磁场测量方法。
发明内容
本发明提供的一种大磁场测量方法，包括：中大磁场测量步骤及极大磁场测量步骤；另外还包括：
步骤1：将四个正交配置的磁阻电阻放置到外加磁场中，并获取各个磁阻电阻的阻值；第一磁阻电阻与第三磁阻电阻位于一条直线上，第二磁阻电阻与第四磁阻电阻位于另一条直线上，所述一条直线与所述另一条直线垂直；
步骤2：若检测到四个磁阻电阻的阻值相对于磁场为0时的阻值变化量小于设定值时，则采用小磁场测量步骤对外加磁场进行测量；若检测到四个磁阻电阻的阻值都变小，则采用极大磁场测量步骤对外加磁场进行测量；
若四个磁阻电阻的阻值均不满足上述两个判断条件，则将其中两个相互正交的磁阻电阻的阻值带入中大磁场测量步骤计算，若计算过程收敛则判断外加磁场为中大磁场且计算结果为中大磁场的磁场强度及方向；若计算过程不收敛则将四个磁阻电阻的阻值带入极大磁场测量步骤计算，且判断外加磁场为极大磁场，计算结果为极大磁场的磁场强度及方向；
其中，中大磁场测量步骤进一步包括：
步骤M1：获取外加磁场中两个相互正交的磁阻电阻的阻值，同时将无磁场时这两个磁阻电阻的初始参考层磁化方向作为给定的参考层磁化方向
Figure PCTCN2017090548-appb-000001
Figure PCTCN2017090548-appb-000002
步骤M2：根据两个磁阻电阻的阻值分别计算两个磁阻电阻的自由层磁化方向和参考层磁化方向的夹角；
步骤M3：分别根据两个磁阻电阻的给定参考层磁化方向
Figure PCTCN2017090548-appb-000003
及两个磁阻电阻的自由层磁化方向和参考层磁化方向的夹角计算出两个磁阻电阻的自由层磁化方向；
步骤M4：根据两个磁阻电阻的给定参考层磁化方向、两个磁阻电阻的自由层磁化方向求解外加磁场的磁场幅值及方向；
步骤M5：将本次计算得到的外加磁场的磁场幅值及方向与前一次计算结 果相比，若两次结果的差值大于设定阈值，则根据本次计算得到的外加磁场的磁场幅值及方向更新两个磁阻电阻的参考层磁化方向并将其作为新的给定的参考层磁化方向
Figure PCTCN2017090548-appb-000004
并再次执行步骤M2～步骤M5，直到两次结果的差值小于设定值；
极大磁场测量步骤进一步包括：
步骤N1：根据四个磁阻电阻的阻值计算各磁阻电阻自由层磁化方向与参考层磁化方向的夹角；
步骤N2：根据第一磁阻电阻的自由层磁化方向与参考层磁化方向的夹角以及第三磁阻电阻的自由层磁化方向与参考层磁化方向的夹角计算外加磁场的磁场强度H1及方向θ1；根据第二磁阻电阻的自由层磁化方向与参考层磁化方向的夹角以及第四磁阻电阻的自由层磁化方向与参考层磁化方向的夹角计算外加磁场的磁场强度H2及方向θ2；
步骤N3：根据磁场强度H1与磁场强度H2确定外加磁场最终的磁场强度H0，根据方向θ2与方向θ1确定外加磁场最终的方向θ。
小磁场测量步骤进一步包括：
步骤S1：采集位于待测磁场中两个相互正交的磁阻电阻的阻值R1，R2；
步骤S2：将其中一个磁阻电阻的阻值R1及其固有参数带入公式R＝kmcos(θ-θ0)H0+R0，将另一个磁阻电阻的阻值R2及其固有参数带入公式R＝kmcos(θ-θ0-θ′)H0+R0得到二元方程组：
其中，R为置于待测磁场中磁阻电阻的阻值，H0为待测量磁场的磁场强度，θ为待测磁场的磁场方向，R0为零磁场时磁阻电阻的阻值；
Figure PCTCN2017090548-appb-000005
式中，
Figure PCTCN2017090548-appb-000006
分别为磁阻电阻置于零磁场时自由层的饱和磁化方向以及参考层的饱和磁化方向；
Figure PCTCN2017090548-appb-000007
式中，HAF、 HAR分别为磁阻电阻自由层的各项异性场幅值及参考层的各项异性场幅值；hBF＝HBF/HAF，HBF、θBF分别为磁阻电阻自由层的内部偏置磁场幅值及方向；hBR＝HBR/HAR，HBR、θBR分别为磁阻电阻参考层的内部偏置磁场幅值及方向；
步骤S3：求解步骤2中的二元方程组，得到待测量磁场的磁场强度H0及方向θ。
进一步，若重复执行步骤M2～步骤M5设定次数后，本次计算结果与前次计算结果的差值仍然不小于设定值，则认为中大磁场测量步骤的计算过程不收敛。
进一步，极大磁场测量步骤还包括步骤N4：根据方向θ对磁场强度H0进行优化。
本发明提供的一种大磁场测量装置，包括：小磁场测量模块、中大磁场测量模块及极大磁场测量模块；另外还包括：
磁阻电阻阻值获取模块，用于获取外加磁场中四个正交配置的磁阻电阻的阻值；第一磁阻电阻与第三磁阻电阻位于一条直线上，第二磁阻电阻与第四磁阻电阻位于另一条直线上，所述一条直线与所述另一条直线垂直；
磁场计算模块，用于判断：若检测到四个磁阻电阻的阻值相对于磁场为0时的阻值变化量小于设定值时，则调用小磁场测量模块对外加磁场进行测量；若检测到四个磁阻电阻的阻值都变小，则调用极大磁场测量模块对外加磁场进行测量；
若四个磁阻电阻的阻值均不满足上述两个判断条件，则将其中两个相互正交的磁阻电阻的阻值带入中大磁场测量模块计算，若计算过程收敛则判断外加磁场为中大磁场且计算结果为中大磁场的磁场强度及方向；若计算过程不收敛则将四个磁阻电阻的阻值带入极大磁场测量模块计算，且判断外加磁场为极大磁场，计算结果为极大磁场的磁场强度及方向；
其中，中大磁场测量模块进一步包括：
初始化子模块，用于获取外加磁场中两个相互正交的磁阻电阻的阻值，同 时将无磁场时这两个磁阻电阻的初始参考层磁化方向作为给定的参考层磁化方向
Figure PCTCN2017090548-appb-000008
自由层及参考层夹角计算子模块，用于根据两个磁阻电阻的阻值分别计算两个磁阻电阻的自由层磁化方向和参考层磁化方向的夹角；
自由层磁化方向计算子模块，用于分别根据两个磁阻电阻的给定参考层磁化方向
Figure PCTCN2017090548-appb-000009
及两个磁阻电阻的自由层磁化方向和参考层磁化方向的夹角计算出两个磁阻电阻的自由层磁化方向；
外加磁场计算子模块，根据两个磁阻电阻的给定参考层磁化方向、两个磁阻电阻的自由层磁化方向求解外加磁场的磁场幅值及方向；
精度判断子模块，用于将本次计算得到的外加磁场的磁场幅值及方向与前一次计算结果相比，若两次结果的差值大于设定阈值，则根据本次计算得到的外加磁场的磁场幅值及方向更新两个磁阻电阻的参考层磁化方向并将其作为新的给定的参考层磁化方向
Figure PCTCN2017090548-appb-000010
并再次执行自由层及参考层夹角计算子模块、自由层磁化方向计算子模块、外加磁场计算子模块及精度判断子模块，直到两次结果的差值小于设定值；
极大磁场测量模块进一步包括：
磁阻电阻自由层磁化方向与参考层磁化方向夹角计算子模块，用于根据四个磁阻电阻的阻值计算各磁阻电阻自由层磁化方向与参考层磁化方向的夹角；
外加磁场的磁场强度及方向预计算子模块，用于根据第一磁阻电阻的自由层磁化方向与参考层磁化方向的夹角以及第三磁阻电阻的自由层磁化方向与参考层磁化方向的夹角计算外加磁场的磁场强度H1及方向θ1；根据第二磁阻电阻的自由层磁化方向与参考层磁化方向的夹角以及第四磁阻电阻的自由层磁化方向与参考层磁化方向的夹角计算外加磁场的磁场强度H2及方向θ2；
外加磁场的磁场强度及方向确定子模块，用于根据磁场强度H1与磁场强度H2确定外加磁场最终的磁场强度H0，根据方向θ2与方向θ1确定外加磁场最终的方向θ。
所述小磁场测量模块进一步包括：
磁阻电阻阻值获取子模块，用于获取位于待测磁场中两个相互正交的磁阻电阻的阻值R1，R2；
小磁场方程组建立子模块，用于将其中一个磁阻电阻的阻值R1及其固有参数带入公式R＝kmcos(θ-θ0)H0+R0，将另一个磁阻电阻的阻值R2及其固有参数带入公式R＝kmcos(θ-θ0-θ′)H0+R0得到二元方程组：
其中，R为置于待测磁场中磁阻电阻的阻值，H0为待测量磁场的磁场强度，θ为待测磁场的磁场方向，R0为零磁场时磁阻电阻的阻值；
Figure PCTCN2017090548-appb-000011
式中，
Figure PCTCN2017090548-appb-000012
分别为磁阻电阻置于零磁场时自由层的饱和磁化方向以及参考层的饱和磁化方向；
Figure PCTCN2017090548-appb-000013
式中，HAF、HAR分别为磁阻电阻自由层的各项异性场幅值及参考层的各项异性场幅值；hBF＝HBF/HAF，HBF、θBF分别为磁阻电阻自由层的内部偏置磁场幅值及方向；hBR＝HBR/HAR，HBR、θBR分别为磁阻电阻参考层的内部偏置磁场幅值及方向；
小磁场测量方程组求解子模块，用于求解所述二元方程组，得到待测量磁场的磁场强度H0及方向θ；
进一步，若重复执行自由层及参考层夹角计算子模块、自由层磁化方向计算子模块、外加磁场计算子模块及精度判断子模块设定次数后，本次计算结果与前次计算结果的差值仍然不小于设定值，则认为中大磁场测量模块的计算过程不收敛。
进一步，极大磁场测量模块还包括磁场强度优化子模块，用于根据方向θ对磁场强度H0进行优化。
综上所述，由于采用了上述技术方案，本发明的有益效果是：
本发明提供的大磁场测量方法实现了对大磁场的准确测量，测量范围扩展 到2mOe～2500Oe，动态范围达6个数量级，特别是可测最大磁场从传统的数十奥斯特扩展到数千奥斯特，扩展40倍左右。
附图说明
本发明将通过例子并参照附图的方式说明，其中：
图1为外加磁场中磁阻电阻的分布图。
图2为本发明方法流程图。
图3为隧穿磁阻单畴模型。
图4为小磁场环境中隧穿磁阻电阻自由层与参考层贡献的灵敏度随角度变化的仿真图。
图5为中大磁场测量步骤的流程图。
图6为磁阻电阻的单畴行为的归一化星形曲线示意图。
图7为极大磁场测量矢量图。
具体实施方式
本说明书中公开的所有特征，或公开的所有方法或过程中的步骤，除了互相排斥的特征和/或步骤以外，均可以以任何方式组合。
本说明书中公开的任一特征，除非特别叙述，均可被其他等效或具有类似目的的替代特征加以替换。即，除非特别叙述，每个特征只是一系列等效或类似特征中的一个例子而已。
首先，在外加磁场中放置四个正交配置的磁阻电阻(I以下简称为电阻)，布置如图1所示。其中电阻R1与电阻R3位于一条直线上，电阻R2与电阻R4位于另一条直线上，两条直线正交。
如图2，本发明提供的一种大磁场测量方法，包括：
步骤1：获取前述四个磁阻电阻的阻值。
步骤2：若检测到四个磁阻电阻的阻值相对于磁场为0时的阻值变化量小于设定值时，根据不同的技术精度要求设定值是可调的，如2％～5％，认为外界磁场很小，则调用小磁场测量模块对外加磁场进行测量；若检测到四个磁阻电阻的阻值都变小，则直接调用极大磁场测量模块对外加磁场进行测量；
若四个磁阻电阻的阻值均不满足上述两个判断条件，则将其中两个相互正交的磁阻电阻的阻值，如R1与R2或者R3或R4，带入中大磁场测量步骤计算，若计算过程收敛则判断外加磁场为中大磁场且计算结果为中大磁场的磁场强度及方向；若计算过程不收敛则将四个磁阻电阻的阻值带入极大磁场测量步骤计算，且判断外加磁场为极大磁场，计算结果为极大磁场的磁场强度及方向。
下面分别介绍小磁场测量步骤、中大磁场测量步骤及极大磁场测量步骤。
小磁场测量步骤
小磁场测量可采用现有的测量技术，为了获取更高的测量精度，在本发明一个优选实施例中采用以下步骤进行。
测量位于待测小磁场中两个正交磁阻电阻的阻值R1、R2。当然也可以获取R3、R4进计算。本实施例以阻值R1、R2进行计算。
将其中一个磁阻电阻的阻值R1及其固有参数带入公式R＝kmcos(θ-θ0)H0+R0，将另一个磁阻电阻的阻值R2及其固有参数带入公式R＝kmcos(θ-θ0-θ′)H0+R0得到二元方程组：
其中，R为置于待测磁场中磁阻电阻的阻值，H0为待测量磁场的磁场强度，θ为待测磁场的磁场方向，R0为零磁场时磁阻电阻的阻值；
Figure PCTCN2017090548-appb-000014
式中，
Figure PCTCN2017090548-appb-000015
分别为磁阻电阻置于零磁场时自由层的饱和磁化方向以及参考层的饱和磁化方向；
式中，HAF、 HAR分别为磁阻电阻自由层的各项异性场幅值及参考层的各项异性场幅值；hBF＝HBF/HAF，HBF、θBF分别为磁阻电阻自由层的内部偏置磁场幅值及方向；hBR＝HBR/HAR，HBR、θBR分别为磁阻电阻参考层的内部偏置磁场幅值及方向。
即最后得到的两个方程为：
R1＝km1cos(θ-θ01)H0+R01；R2＝km2cos(θ-θ02-θ′)H0+R02；
其中，R01为零磁场时第一磁阻电阻的阻值，可以测试得到。
Figure PCTCN2017090548-appb-000017
Figure PCTCN2017090548-appb-000018
式中，
Figure PCTCN2017090548-appb-000019
分别为第一磁阻电阻置于零磁场时自由层的饱和磁化方向以及参考层的饱和磁化方向，
Figure PCTCN2017090548-appb-000020
均可在零磁场时测得。
Figure PCTCN2017090548-appb-000021
式中，HAF1、HAR1分别为第一磁阻电阻自由层的各项异性场幅值及参考层的各项异性场幅值；hBF1＝HBF1/HAF1，HBF1、θBF1分别为第一磁阻电阻自由层的内部偏置磁场幅值及方向；hBR1＝HBR1/HAR1，HBR1、θBR1分别为第一磁阻电阻参考层的内部偏置磁场幅值及方向，这些值为磁阻电阻固有的参数，可以测得也可以直接从磁阻电阻厂商提供的数据手册中获取。
同样的方式，将第二磁阻的相关参数带入，得到km2及θ02。
计算上述两个方程组成的方程组的解，便得到待测小磁场的磁场强度H0及方向θ。
本发明方法适用各类磁阻电阻，包括隧穿磁阻电阻、巨磁阻电阻以及自旋阀结构磁阻电阻等。
下面以隧穿磁阻电阻为例，阐述上述方法的推导过程，以便本领域技术人 员更好的理解本发明。
在小磁场范围测量情况下，由于外加磁场远小于参考层和被钉扎层内部偏置场，钉扎层和参考层几乎不变，自由层和参考层间的耦合能可计入自由层计算。自由层和参考层均可简化为图3中最简单的模型，且可分开计算。令易轴角度α＝0，则自由层和参考层的磁化方向为：
Figure PCTCN2017090548-appb-000022
式中，hF＝H/HAF，hR＝H/HAR，
Figure PCTCN2017090548-appb-000023
分别为隧穿磁阻电阻自由层的饱和磁化强度、参考层的饱和磁化强度。
无外界磁场时，各层磁化方向满足：
Figure PCTCN2017090548-appb-000024
其中自由层磁化方向满足：
Figure PCTCN2017090548-appb-000025
当外界磁场方向不变时，自由层磁化方向满足：
Figure PCTCN2017090548-appb-000026
则在外界磁场为零时的导数满足：
Figure PCTCN2017090548-appb-000027
相应地，参考层在外界磁场为零时的导数满足：
Figure PCTCN2017090548-appb-000028
可知，隧穿磁阻电阻灵敏度包括两个分量：自由层分量和参考层分量。每个分量的最大灵敏度方向分别垂直于其初始的磁化方向。
因此，隧穿磁阻电阻在外界磁场为零时的导数满足：
Figure PCTCN2017090548-appb-000029
Figure PCTCN2017090548-appb-000030
为归一化后的隧穿磁阻电阻的灵敏度，Ravg＝(Rmax+Rmin)/2，为平均电阻；Δmax＝(Rmax-Rmin)/Ravg，为最大磁电阻变化率。当磁阻电阻的自由层和参考层磁化方向相同时，电阻值最小，为Rmin，当自由层和参考层磁化方向相反时，电阻值最大，为Rmax。
对式(1)进行仿真，得到图4的结果。通常，参考层由被钉扎层强耦合在难轴方向，耦合场典型值高达数千高斯，远大于外加磁场，参考层磁化方向随外界磁场变化很小。隧穿磁阻由自由层和参考层贡献的灵敏度随角度变化如图3，图中FL表示自由层灵敏度，RL表示参考层灵敏度，仿真设置hBXF(＝HBRcos(θBR))＝hBXR(＝HBRsin(θBR))＝1。总灵敏度为自由层和参考层分量的叠加，叠加后，即FL+RL，仍为正弦形式变化。从图3可以看出，隧穿磁阻电阻的最大灵敏度方向并非在磁场方向的90°，而是在90°之前，正弦曲线已出现最大值。
本领域技术人员知晓，在小磁场中隧穿磁阻电阻的阻值R与磁场强度呈线性关系，即
Figure PCTCN2017090548-appb-000031
对式(1)进行变形，令：
Figure PCTCN2017090548-appb-000032
则等式右边变为：
Figure PCTCN2017090548-appb-000033
灵敏度幅值为：
Figure PCTCN2017090548-appb-000034
灵敏度方向为：
Figure PCTCN2017090548-appb-000035
最终等式为：
Figure PCTCN2017090548-appb-000036
进一步，得到公式R＝kmcos(θ-θ0)H0+R0。
中大磁场测量步骤
如图5，中大磁场测量步骤包括：
(1)对于任一外加磁场，测量得到两个不同易轴方向的磁阻电阻，本实施例使用的是相互正交的电阻R1及电阻R2的阻值，同时将两个电阻在无磁场时的初始参考层磁化方向作为给定方向
Figure PCTCN2017090548-appb-000037
需要说明的是磁阻的核心典型结构包括反铁磁层(钉扎层)/铁磁层(被钉扎层)/非磁性金属/铁磁层(参考层)/势垒层/铁磁层(自由层)，电流垂直膜面。其中，参考层和被钉扎层通过一层非常薄的非磁性金属诱导形成人工合成反铁磁结构，使得参考层和被钉扎层的磁化方向更加稳定，不易受到外界强磁场破坏。而自由层的磁化方向随外界磁场变化而变化。
若磁阻电阻沿某一轴或方向最容易被磁化则称为易轴，反之则谓难轴。
磁阻电阻的阻值能够随外加磁场的变化而变化，因此测量其阻值便可测量外加磁场。将两个具有不同易轴方向的磁阻电阻放置于外加磁场中，通过全桥或其他电阻测量电路可得到两个电阻的阻值。
(2)根据两个电阻的阻值，可以计算得到各个电阻自由层磁化方向和参考层磁化方向的夹角
Figure PCTCN2017090548-appb-000038
对应如图5过程①，计算公式为：
Figure PCTCN2017090548-appb-000039
其中
Figure PCTCN2017090548-appb-000040
为第一个磁阻电阻的自由层磁化方向，R1min为第一个磁阻电阻的最小值，R1max为第一个磁阻电阻的最大值。
Figure PCTCN2017090548-appb-000041
其中
Figure PCTCN2017090548-appb-000042
为第二个磁阻电阻的自由层磁化方向，R2min为第二个磁阻电阻的最小值，R2max为第二个磁阻电阻的最大值。
当自由层和参考层磁化方向相同时，磁阻电阻值最小，为Rmin，当自由层和参考层磁化方向相反时，电阻值最大，为Rmax。R1min、R1max为第一磁阻电阻的最小值及最大值，R2min、R2max为第二磁阻电阻的最小值及最大值，均可通过分别标定两个磁阻电阻得到。
(3)对于给定的参考层磁化方向，计算自由层磁化方向
Figure PCTCN2017090548-appb-000043
如图5过程②，计算公式为
Figure PCTCN2017090548-appb-000044
将
Figure PCTCN2017090548-appb-000045
带入前式便得到第一磁阻电阻的自由层磁化方向
Figure PCTCN2017090548-appb-000046
将
Figure PCTCN2017090548-appb-000047
带入前式便得到第二磁阻电阻的自由层磁化方向
Figure PCTCN2017090548-appb-000048
式中，S1，S2分别表示自由层磁畴处于图6中的易轴正方向范围(-π/2～π/2)或者易轴负方向范围(π/2～3π/2)。对于特定的磁阻电阻其自由层磁畴的状态是唯一的。
对于隧穿磁阻电阻来说，当隧穿磁阻电阻自由层的内部易轴偏置磁场大于 各向异性场时，按照本发明中四个磁阻电阻的布设方式，就能确保其中总至少有两个相互正交的磁阻电阻的自由层磁畴处于S1状态，选择状态已知的两个电阻计算中大磁场，则可以确定两者的自由层磁化方向
Figure PCTCN2017090548-appb-000049
而在制作内部易轴偏置磁场大于各向异性场的隧穿磁阻电阻工艺是现有的。
(4)根据计算得到的自由层磁化方向
Figure PCTCN2017090548-appb-000050
计算被测磁场幅值和方向hF，θ，如图5过程③，计算公式为式：
Figure PCTCN2017090548-appb-000051
式中，式中α1，α2分别为两个磁阻电阻的易轴方向，hJFR为任意一个磁阻电阻的自由层与参考层的耦合场，hBF＝HBF/HAF，HBF为磁阻电阻自由层的内部偏置磁场大小，HAF为自由层各向异性场大小；θBF为自由层的内部偏置磁场方向。本实施例中的四个磁阻电阻相同，因此认为它们的固有参数也是相同的。在计算时，选取任意一个磁阻电阻的固有参数即可。
(5)针对计算得到的磁场参数与前一次结果比较，是否达到精度要求(本实施例中，当两次计算结果中磁场强度的差值小于1E-4，方向的差值小于0.01°时认为达到精度要求)，达到要求则输出结果；否则根据磁场计算更新参考层磁化方向角度
Figure PCTCN2017090548-appb-000052
如图5过程④，并返回步骤(2)继续迭代。
其中更新参考层磁化方向角度的步骤为：
求解一元四次方程
Figure PCTCN2017090548-appb-000053
其中hX1，hY1分别为外加磁场在第一磁阻电阻易轴和难轴方向上的磁场，二者根据步骤4的计算结果得到，hX1＝hFcosθ，hY1＝hFsinθ；
Figure PCTCN2017090548-appb-000054
上述一元四次方程具有4个解，当隧穿磁阻处于稳定平衡状态时，
Figure PCTCN2017090548-appb-000055
只 有一个解。该解取决于3个条件：
1)x1为实数且|x1|≤1；
Figure PCTCN2017090548-appb-000056
3)该解与隧穿磁阻的初始位置间所有角度能量必须小于初始位置的能量。
求解一元四次方程
Figure PCTCN2017090548-appb-000057
其中hX2，hY2分别为外加磁场在第二磁阻电阻易轴和难轴方向上的磁场，二者根据步骤4的计算结果得到，由于第一磁阻电阻与第二磁阻电阻正交，因此hX2＝hFsinθ，hY2＝hFcosθ；
Figure PCTCN2017090548-appb-000058
与
Figure PCTCN2017090548-appb-000059
的筛选过程同理，确定
Figure PCTCN2017090548-appb-000060
将求解得到的
Figure PCTCN2017090548-appb-000061
值分别作为新的给定的参考层磁化方向
Figure PCTCN2017090548-appb-000062
在其他实施例中，可以借助计算机数值方法进行求解以下公式得到磁阻电阻的参考层磁化方向角度，即将技术人员认为可能的角度带入下列公式计算，判断其结果是否接近0，如是则认为带入的角度为
Figure PCTCN2017090548-appb-000063
的解：
Figure PCTCN2017090548-appb-000064
hX，hY分别为外加磁场在磁阻电阻易轴和难轴方向上的磁场。上式为隧穿磁阻单畴模型计算在参考层的磁化方向角度的一般表达式，令
Figure PCTCN2017090548-appb-000065
上式可演化为：
Figure PCTCN2017090548-appb-000066
亦即前一实施例计算参考层磁化方向的公式。但是使用计算机数值方法求解会存在精度、时间和全局收敛性问题，因此推荐使用前一实施例计算磁阻电阻参考层磁化方向。
通过上述迭代，参考层磁化方向将逐渐收敛到真实方向，同时计算得到的外加磁场也收敛到真实的外加磁场。迭代算法的收敛性取决于在计算参考层磁化方向时是否收敛。
若重复迭代设定次数后，计算结果与前次计算结果的差值仍然不小设定值， 则认为计算过程不能收敛，当前的外加磁场为极大磁场。设定次数根据不同的磁阻电阻及计算精度要求设定，本实施例设定的次数是20次。
极大磁场测量步骤
根据图1布置，四个磁阻电阻的极大磁场测量分布图如图7所示。以电阻参考层偏置场方向为参考方向，四个电阻依次旋转90°正交布置。图中H，θ为外加磁场幅值和方向；FL为四个电阻的自由层磁化方向的合成方向，可近似认为均和外加磁场方向相同；四个矢量HBR表示四个磁阻电阻的参考层内部偏置场的幅值和方向，本实施例中四个磁阻电阻相同，因此认为它们的参考层内部偏置场幅值相同，相邻的两个磁阻电阻的参考层内部偏置场方向正交；RL1,2,3,4分别表示为四个电阻的参考层磁化方向，其与外加磁场和各自的参考层内部偏置场的合成方向一致；
Figure PCTCN2017090548-appb-000067
为四个电阻自由层磁化方向和参考层磁化方向的夹角。
由图7的矢量关系，可得四个芯片磁化方向和外加磁场的关系为：
Figure PCTCN2017090548-appb-000068
外加磁场的幅值和方向可通过上述方程组的其中两个计算得到。然而仅有两个电阻无法计算整个二维平面的磁场，如当选择电阻R1和电阻R3计算外加磁场时，显然外加磁场为0°～180°和180°～360°时镜面对称，因此必须先借助另外两个电阻判断外加磁场方向范围，然后选择合适的两个电阻进行计算。
以电阻R1和电阻R3作为一组，可计算得到：
Figure PCTCN2017090548-appb-000069
式中，H1，θ1分别为通过R1和R3计算得到的外加磁场幅值和方向。
以电阻R2和电阻R4作为另一组，可计算得到：
Figure PCTCN2017090548-appb-000070
式中，H2，θ2分别为通过R2和R4计算得到的外加磁场幅值和方向。
通过比较比较上述两式的角度，可得外加磁场幅值和方向为：
H0＝H1＝H2
Figure PCTCN2017090548-appb-000071
上述公式中，各个磁阻电阻自由层磁化方向与参考层磁化方向的夹角计算过程参见中大磁场测量步骤的第(2)步。
经过实验，我们发现通过上述步骤计算得到的极大磁场的磁场强度与实际值具有一定的差别，且其和实际值基本保持线性关系，因此可对其进行修正。
由于前述步骤计算得到的磁场方向基本准确，因此只需对磁场幅值进行修正即可。修正方案为：H＝kH0+b，H0为前述步骤得到的外加磁场的磁场强度，k、b为修正系数，和被测磁场角度相关，H为优化后的磁场幅值。修正系数k和b与被测磁场方向的关系为：
Figure PCTCN2017090548-appb-000072
其他角度范围满足周期特性。
需要说明的是，针对不同的磁阻电阻，修正系数k和b是不同的，需要针对特定的磁阻电阻进行试验测试标定。具体做法是将本发明中计算得到的H0与真实磁场(精度更高的仪器测定的结果)比较，然后通过数值拟合的方法得到H0与真实磁场之间的数值关系。
本发明还提供了一套与上述方法步骤一一对应的软系统。
本发明并不局限于前述的具体实施方式。本发明扩展到任何在本说明书中披露的新特征或任何新的组合，以及披露的任一新的方法或过程的步骤或任何新的组合。

Claims (8)

  1. 一种宽磁场范围测量方法，其特征在于，包括：小磁场测量步骤、中大磁场测量步骤及极大磁场测量步骤；另外还包括：
    步骤1：将四个正交配置的磁阻电阻放置到外加磁场中，并获取各个磁阻电阻的阻值；第一磁阻电阻与第三磁阻电阻位于一条直线上，第二磁阻电阻与第四磁阻电阻位于另一条直线上，所述一条直线与所述另一条直线垂直；
    步骤2：若检测到四个磁阻电阻的阻值相对于磁场为0时的阻值变化量小于设定值时，则采用小磁场测量步骤对外加磁场进行测量；若检测到四个磁阻电阻阻值都变小，则采用极大磁场测量步骤对外加磁场进行测量；
    若四个磁阻电阻的阻值均不满足上述两个判断条件，则将其中两个相互正交的磁阻电阻的阻值带入中大磁场测量步骤计算，若计算过程收敛则判断外加磁场为中大磁场且计算结果为中大磁场的磁场强度及方向；若计算过程不收敛则将四个磁阻电阻的阻值带入极大磁场测量步骤计算，且判断外加磁场为极大磁场，计算结果为极大磁场的磁场强度及方向；
    其中，中大磁场测量步骤进一步包括：
    步骤M1：获取外加磁场中两个相互正交的磁阻电阻的阻值，同时将无磁场时这两个磁阻电阻的初始参考层磁化方向作为给定的参考层磁化方向
    Figure PCTCN2017090548-appb-100001
    Figure PCTCN2017090548-appb-100002
    步骤M2：根据两个磁阻电阻的阻值分别计算两个磁阻电阻的自由层磁化方向和参考层磁化方向的夹角；
    步骤M3：分别根据两个磁阻电阻的给定参考层磁化方向
    Figure PCTCN2017090548-appb-100003
    及两个磁阻电阻的自由层磁化方向和参考层磁化方向的夹角计算出两个磁阻电阻的自由层磁化方向；
    步骤M4：根据两个磁阻电阻的给定参考层磁化方向、两个磁阻电阻的自由层磁化方向求解外加磁场的磁场幅值及方向；
    步骤M5：将本次计算得到的外加磁场的磁场幅值及方向与前一次计算结果相比，若两次结果的差值大于设定阈值，则根据本次计算得到的外加磁场的 磁场幅值及方向更新两个磁阻电阻的参考层磁化方向并将其作为新的给定的参考层磁化方向
    Figure PCTCN2017090548-appb-100004
    并再次执行步骤M2～步骤M5，直到两次结果的差值小于设定值；
    极大磁场测量步骤进一步包括：
    步骤N1：根据四个磁阻电阻的阻值计算各磁阻电阻自由层磁化方向与参考层磁化方向的夹角；
    步骤N2：根据第一磁阻电阻的自由层磁化方向与参考层磁化方向的夹角以及第三磁阻电阻的自由层磁化方向与参考层磁化方向的夹角计算外加磁场的磁场强度H1及方向θ1；根据第二磁阻电阻的自由层磁化方向与参考层磁化方向的夹角以及第四磁阻电阻的自由层磁化方向与参考层磁化方向的夹角计算外加磁场的磁场强度H2及方向θ2；
    步骤N3：根据磁场强度H1与磁场强度H2确定外加磁场最终的磁场强度H0，根据方向θ2与方向θ1确定外加磁场最终的方向θ。
  2. 根据权利要求1所述的一种宽磁场范围测量方法，其特征在于，小磁场测量步骤进一步包括：
    步骤S1：采集位于待测磁场中两个相互正交的磁阻电阻的阻值R1，R2；
    步骤S2：将其中一个磁阻电阻的阻值R1及其固有参数带入公式R＝kmcos(θ-θ0)H0+R0，将另一个磁阻电阻的阻值R2及其固有参数带入公式R＝kmcos(θ-θ0-θ′)H0+R0得到二元方程组：
    其中，R为置于待测磁场中磁阻电阻的阻值，H0为待测量磁场的磁场强度，θ为待测磁场的磁场方向，R0为零磁场时磁阻电阻的阻值；
    Figure PCTCN2017090548-appb-100005
    式中，
    Figure PCTCN2017090548-appb-100006
    分别为磁阻电阻置于零磁场时自由层的饱和磁化方向以及参考层的饱和磁化方向；
    Figure PCTCN2017090548-appb-100007
    式中，HAF、 HAR分别为磁阻电阻自由层的各项异性场幅值及参考层的各项异性场幅值；hBF＝HBF/HAF，HBF、θBF分别为磁阻电阻自由层的内部偏置磁场幅值及方向；hBR＝HBR/HAR，HBR、θBR分别为磁阻电阻参考层的内部偏置磁场幅值及方向；
    步骤S3：求解步骤2中的二元方程组，得到待测量磁场的磁场强度H0及方向θ；
  3. 根据权利要求1所述的一种宽磁场范围测量方法，其特征在于，若重复执行步骤M2～步骤M5设定次数后，本次计算结果与前次计算结果的差值仍然不小于设定值，则认为中大磁场测量步骤的计算过程不收敛。
  4. 根据权利要求1所述的一种宽磁场范围测量方法，其特征在于，极大磁场测量步骤还包括步骤N4：根据方向θ对磁场强度H0进行优化。
  5. 一种宽磁场范围测量装置，其特征在于，包括：小磁场测量模块、中大磁场测量模块及极大磁场测量模块；另外还包括：
    磁阻电阻阻值获取模块，用于获取外加磁场中四个正交配置的磁阻电阻的阻值；第一磁阻电阻与第三磁阻电阻位于一条直线上，第二磁阻电阻与第四磁阻电阻位于另一条直线上，所述一条直线与所述另一条直线垂直；
    磁场计算模块，用于判断：若检测到四个磁阻电阻的阻值相对于磁场为0时的阻值变化量小于设定值时，则调用小磁场测量模块对外加磁场进行测量；若检测到四个磁阻电阻的阻值都变小，则调用极大磁场测量模块对外加磁场进行测量；
    若四个磁阻电阻的阻值均不满足上述两个判断条件，则将其中两个相互正交的磁阻电阻的阻值带入中大磁场测量模块计算，若计算过程收敛则判断外加磁场为中大磁场且计算结果为中大磁场的磁场强度及方向；若计算过程不收敛则将四个磁阻电阻的阻值带入极大磁场测量模块计算，且判断外加磁场为极大磁场，计算结果为极大磁场的磁场强度及方向；
    其中，中大磁场测量模块进一步包括：
    初始化子模块，用于获取外加磁场中两个相互正交的磁阻电阻的阻值，同 时将无磁场时这两个磁阻电阻的初始参考层磁化方向作为给定的参考层磁化方向
    Figure PCTCN2017090548-appb-100008
    自由层及参考层夹角计算子模块，用于根据两个磁阻电阻的阻值分别计算两个磁阻电阻的自由层磁化方向和参考层磁化方向的夹角；
    自由层磁化方向计算子模块，用于分别根据两个磁阻电阻的给定参考层磁化方向
    Figure PCTCN2017090548-appb-100009
    及两个磁阻电阻的自由层磁化方向和参考层磁化方向的夹角计算出两个磁阻电阻的自由层磁化方向；
    外加磁场计算子模块，根据两个磁阻电阻的给定参考层磁化方向、两个磁阻电阻的自由层磁化方向求解外加磁场的磁场幅值及方向；
    精度判断子模块，用于将本次计算得到的外加磁场的磁场幅值及方向与前一次计算结果相比，若两次结果的差值大于设定阈值，则根据本次计算得到的外加磁场的磁场幅值及方向更新两个磁阻电阻的参考层磁化方向并将其作为新的给定的参考层磁化方向
    Figure PCTCN2017090548-appb-100010
    并再次执行自由层及参考层夹角计算子模块、自由层磁化方向计算子模块、外加磁场计算子模块及精度判断子模块，直到两次结果的差值小于设定值；
    极大磁场测量模块进一步包括：
    磁阻电阻自由层磁化方向与参考层磁化方向夹角计算子模块，用于根据四个磁阻电阻的阻值计算各磁阻电阻自由层磁化方向与参考层磁化方向的夹角；
    外加磁场的磁场强度及方向预计算子模块，用于根据第一磁阻电阻的自由层磁化方向与参考层磁化方向的夹角以及第三磁阻电阻的自由层磁化方向与参考层磁化方向的夹角计算外加磁场的磁场强度H1及方向θ1；根据第二磁阻电阻的自由层磁化方向与参考层磁化方向的夹角以及第四磁阻电阻的自由层磁化方向与参考层磁化方向的夹角计算外加磁场的磁场强度H2及方向θ2；
    外加磁场的磁场强度及方向确定子模块，用于根据磁场强度H1与磁场强度H2确定外加磁场最终的磁场强度H0，根据方向θ2与方向θ1确定外加磁场最终的方向θ。
  6. 根据权利要求5所述的一种宽磁场范围测量装置，其特征在于，所述小 磁场测量模块进一步包括：
    磁阻电阻阻值获取子模块，用于获取位于待测磁场中两个相互正交的磁阻电阻的阻值R1，R2；
    小磁场方程组建立子模块，用于将其中一个磁阻电阻的阻值R1及其固有参数带入公式R＝kmcos(θ-θ0)H0+R0，将另一个磁阻电阻的阻值R2及其固有参数带入公式R＝kmcos(θ-θ0-θ′)H0+R0得到二元方程组：
    其中，R为置于待测磁场中磁阻电阻的阻值，H0为待测量磁场的磁场强度，θ为待测磁场的磁场方向，R0为零磁场时磁阻电阻的阻值；
    Figure PCTCN2017090548-appb-100011
    式中，
    Figure PCTCN2017090548-appb-100012
    分别为磁阻电阻置于零磁场时自由层的饱和磁化方向以及参考层的饱和磁化方向；
    Figure PCTCN2017090548-appb-100013
    式中，HAF、HAR分别为磁阻电阻自由层的各项异性场幅值及参考层的各项异性场幅值；hBF＝HBF/HAF，HBF、θBF分别为磁阻电阻自由层的内部偏置磁场幅值及方向；hBR＝HBR/HAR，HBR、θBR分别为磁阻电阻参考层的内部偏置磁场幅值及方向；
    小磁场测量方程组求解子模块，用于求解所述二元方程组，得到待测量磁场的磁场强度H0及方向θ。
  7. 根据权利要求5所述的一种宽磁场范围测量装置，其特征在于，若重复执行自由层及参考层夹角计算子模块、自由层磁化方向计算子模块、外加磁场计算子模块及精度判断子模块设定次数后，本次计算结果与前次计算结果的差值仍然不小于设定值，则认为中大磁场测量模块的计算过程不收敛。
  8. 根据权利要求5所述的一种宽磁场范围测量装置，其特征在于，极大磁场测量模块还包括磁场强度优化子模块，用于根据方向θ对磁场强度H0进行优化。
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