WO2018090634A1 - 一种中大磁场全象限测量方法 - Google Patents

一种中大磁场全象限测量方法 Download PDF

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WO2018090634A1
WO2018090634A1 PCT/CN2017/090545 CN2017090545W WO2018090634A1 WO 2018090634 A1 WO2018090634 A1 WO 2018090634A1 CN 2017090545 W CN2017090545 W CN 2017090545W WO 2018090634 A1 WO2018090634 A1 WO 2018090634A1
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reluctance
magnetic field
state
magnetization direction
resistors
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French (fr)
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欧阳勇
何金良
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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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
    • G01R33/02—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

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  • the invention relates to the field of magnetic field measurement technology, in particular to a method for measuring the magnetic field strength in a large range.
  • the tunneling magnetoresistive resistor has good linearity when the magnetic field to be measured is small, and the measurement accuracy is good, but it is difficult to center the large range (the magnetic field strength is about 4-6H AF , and H AF is the free layer of the magnetoresistive resistor).
  • the magnetic field strength is about 4-6H AF
  • H AF is the free layer of the magnetoresistive resistor.
  • Oe is the magnetic field strength unit - Oersted magnetic field measurement, because: 1) tunneling reluctance
  • the sensing curve of the resistance is linearly saturated in the middle and large range, which is severely nonlinear. It is necessary to establish a nonlinear model for calculation.
  • the reference layer of the tunneling magnetoresistive resistor will rotate significantly, and the influence of the reference layer must be considered. 3) The direction of the tunneling magnetoresistive magnetic domain may be irreversibly reversed, and the resistance value may jump to form different sensing curves of the two bifurcations.
  • the technical problem to be solved by the present invention is to provide a vector measurement method suitable for the tunneling magnetoresistance of a medium-large magnetic field in view of the above problems.
  • a medium and large magnetic field measuring method characterized in that it comprises:
  • Step 1 Place four orthogonally configured reluctance resistors into the applied magnetic field; wherein the first reluctance resistor and the third reluctance resistor are in a straight line, and the second reluctance resistor and the fourth reluctance resistor are located on the other In a straight line, the one straight line is perpendicular to the other straight line; the inner easy axis offset magnetic field of the four magnetoresistive resistor free layers is larger than the anisotropy field;
  • Step 2 Determine the two reluctance resistances of the minimum resistance value, and then determine that the other two reluctance resistors are in the S1 state, and the resistance values of the two reluctance resistors in the S1 state are R 1 , R 2 , and will be
  • the S1 state means that the free layer magnetic domain of the magnetoresistive resistor is in the positive direction of the easy axis;
  • Step 2 Calculate the angle between the free layer magnetization direction of the two reluctance resistors in the S1 state and the reference layer magnetization direction according to the resistance values R 1 and R 2 , respectively;
  • Step 3 According to the magnetization direction of a given reference layer of two reluctance resistors in the S1 state And the angle between the free layer magnetization direction of the two reluctance resistors in the S1 state and the magnetization direction of the reference layer to calculate the free layer magnetization directions of the two reluctance resistors in the S1 state;
  • Step 4 Solving the amplitude and direction of the magnetic field of the applied magnetic field according to the magnetization direction of the given reference layer of the two reluctance resistors in the S1 state and the free layer magnetization directions of the tunneling reluctance resistors in the S1 state;
  • Step 5 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 directions of the two reluctance resistors in the S1 state and use them as the new given reference layer magnetization direction Then perform steps 2 to 5 again until the difference between the two results is less than the set value.
  • step 2 the equations for calculating the angle between the free layer magnetization direction of the two reluctance resistors in the S1 state and the magnetization direction of the reference layer are respectively: among them
  • R 1min is the minimum value of the first magnetoresistive resistor in the S1 state
  • R 1max is the maximum value of the first magnetoresistive resistor in the S1 state.
  • R 2min is the minimum value of the second reluctance resistance in the S1 state
  • R 2max is the second tunneling reluctance resistance in the S1 state. Maximum value.
  • step 3 the free layer magnetization directions of the two reluctance resistors in the S1 state are calculated according to the formula:
  • step 4 the following equations are used to solve the magnetic field amplitude h F and direction ⁇ of the applied magnetic field:
  • ⁇ 1 and ⁇ 2 are the easy axis directions of two reluctance resistors in the S1 state
  • h JFR is the coupling field of the free layer and the reference layer of any reluctance resistor
  • h BF H BF /H AF
  • H BF is the internal bias magnetic field of the free layer of the reluctance resistance
  • H AF is the free layer anisotropy field size
  • ⁇ BF is the direction of the internal bias magnetic field of the free layer.
  • step 5 the reference layer magnetization directions of the two reluctance resistors in the S1 state are updated.
  • the steps further include:
  • x 1 is a real number and
  • x 2 is a real number and
  • the medium and large magnetic field measuring method provided by the invention realizes the accurate measurement of the medium and large magnetic field, and expands the measurement range of the magnetic field strength of the tunneling magnetoresistance resistance.
  • Figure 1 is a flow chart of the method of the present invention.
  • FIG. 2 is a schematic diagram of a normalized asteroid curve of single domain behavior of a tunneling magnetoresistive resistor.
  • Figure 3 is a simulation diagram of the measurement range as a function of the measured magnetic field strength when a magnetic field is measured using two magnetoresistive resistors.
  • FIG. 4 is a schematic structural view of four magnetoresistive resistors disposed in another embodiment of the present invention.
  • Figure 5 is a simulation diagram of the measurement range as a function of the measured magnetic field strength when a magnetic field is measured using four magnetoresistive resistors.
  • the method of the invention is applicable to a magnetoresistive resistor such as a tunneling magnetoresistive resistor and a giant magnetoresistance resistor, and the tunnel is used in this embodiment.
  • the magnetoresistance resistance is taken as an example for explanation.
  • the steps of an embodiment of the method of the present invention include:
  • tunneling magnetoresistance includes antiferromagnetic layer (pinning layer) / ferromagnetic layer (pinned layer) / non-magnetic metal / ferromagnetic layer (reference layer) / barrier layer / iron The magnetic 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.
  • tunneling reluctance resistance is most easily magnetized along an axis or direction, it is called an easy axis, and vice versa.
  • the resistance of the tunneling magnetoresistive resistor can vary with the applied magnetic field, so the applied magnetic field can be measured by measuring its resistance.
  • Two tunneling reluctance 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 tunneling magnetoresistive resistor
  • R 1max is the maximum value of the first tunneling magnetoresistive resistor
  • R 2min is the minimum value of the second tunneling magnetoresistive resistor
  • R 2max is the maximum value of the second tunneling magnetoresistive resistor
  • R 1min , R 1max , R 2min and R 2max can be obtained by respectively calibrating two tunneling 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. 2 .
  • the state of the free layer magnetic domain is unique for a particular magnetoresistive resistor.
  • 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 the calculation of the reference layer Whether to converge when the direction is changed.
  • 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.
  • FIG. 3 is a simulation of the measurement range of the magnetic field direction measurement range with different angles of the measured magnetic field when the magnetic field is measured by the embodiment. It can be seen that when the measured is at 0-90°, the two free-resistance layers of the magnetoresistive resistor are always in the S1 state, and the magnetic domain irreversible rotation does not occur, so the formula used in the step (3) in the iterative algorithm is determined to be the S1 state. The value has a large measurement range; when the measured magnetic field is between 90° and 360°, the magnetic domain may undergo irreversible rotation. At this time, the free layer state of the magnetoresistive resistor is uncertain, and the chip free layer cannot be determined in advance. status.
  • step (3) of the iterative algorithm is fixed to the value in the S1 state, when the magnetic field is small, the free layer of the chip is still in the S1 state, and the iterative algorithm is effective; and when the magnetic field is large, the irreversible rotation occurs due to the magnetic domain. Finally, the iterative algorithm converges to the wrong value or does not converge. Therefore, in the case of only two chips, the measurement range when the measured magnetic field is 90° to 360° depends on the distance from the internal bias field of the free layer to the star curve, and the magnetic domain rotation is reversible continuously. Usually, the internal bias field of the free layer is small, and the distance from the star curve is very short, so the measurement range from 90° to 360° is small.
  • the measurement range of 90° to 360° is expanded, and the other two orthogonally arranged chips R 3 and R 4 are added , and the four chip arrangements are as shown in FIG. 4 .
  • the internal easy axis offset magnetic field of the above four tunneling magnetoresistive free layers is larger than the anisotropy field (h BXF >1), at least two tunneling magnetoresistive free layers are in the S1 state, facing the respective easy axes.
  • the positive direction allows the two resistors to be iteratively calculated to obtain a larger measurement range. It is also achievable by those skilled in the art to make the internal easy axis bias magnetic field of the free layer larger than the tunneling reluctance resistance of the anisotropy field.
  • the two tunneling magnetoresistance resistances of the measured magnetic field in the negative direction of the hard axis are the smallest, and the two resistors in the S1 state can be determined by the two resistors.
  • the measured magnetic field tends to its negative axis negative direction, and the two resistance values are the lowest, and the measured relative directions of R 1 and R 2 are measured.
  • the magnetic field tends to be in the positive direction of the easy axis, and is located outside the asteroid curve, and its magnetic domain state tends to be in the positive direction of the easy axis, in the S1 state.
  • Figure 6 shows a simulation of the measurement range of a magnetic field measured with four magnetoresistive resistors as a function of the direction of the measured magnetic field. Compared with Fig. 3, four reluctance resistors are used to measure the external magnetic field. When the direction of the external magnetic field is in the range of 90° to 360°, a larger measurement range can be obtained.
  • Fig. 7 shows the state of each reluctance resistance in the direction of different magnetic fields to be measured when four reluctance resistors are arranged as shown in Fig. 4. In practical use, it is not necessary to strictly refer to this table, and only two resistances in the S1 state can be determined according to the resistance value of the actually measured resistance.
  • 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

一种中大磁场全象限测量方法，涉及磁场测量技术领域。包括：将四个正交配置的磁阻电阻放置到外加磁场中；确定最小阻值的两个磁阻电阻，进而确定另外两个磁阻电阻处于S1状态，并令处于S1状态的两个磁阻电阻的阻值为R 1，R 2，同时将无磁场时这个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；根据这两个磁阻电阻的阻值分别计算这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；分别根据这两个磁阻电阻的给定参考层磁化方向及自由层磁化方向和参考层磁化方向的夹角计算出这两个磁阻电阻的自由层磁化方向；根据这两个磁阻电阻的给定参考层磁化方向、自由层磁化方向求解外加磁场的磁场幅值及方向。

Description

一种中大磁场全象限测量方法 技术领域
本发明涉及磁场测量技术领域，尤其是一种针对中大范围的磁场强度的测量方法。
背景技术
隧穿磁阻电阻在待测磁场较小时具有良好的线性度，测量精度较好，但是其难以对中大范围(磁场强度约为4～6HAF，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)的磁场进行测量，这是因为：1)隧穿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)隧穿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)隧穿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。
发明内容
本发明所要解决的技术问题是：针对上述存在的问题，提供一种适用于中大磁场的隧穿磁阻的矢量测量方法。
本发明提供的中大磁场测量方法，包括：
一种中大磁场测量方法，其特征在于，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；其中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；四个磁阻电阻自由层的内部易轴偏置磁场大于各向异性场；
步骤2：确定最小阻值的两个磁阻电阻，进而确定另外两个磁阻电阻处于 S1状态，并令处于S1状态的两个磁阻电阻的阻值为R1，R2，同时将无磁场时处于S1状态的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 PCTCN2017090545-appb-000001
S1状态是指磁阻电阻的自由层磁畴处于易轴正方向；
步骤2：根据阻值R1，R2分别计算两个处于S1状态的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3：分别根据两个处于S1状态的磁阻电阻的给定参考层磁化方向
Figure PCTCN2017090545-appb-000002
Figure PCTCN2017090545-appb-000003
及两个处于S1状态的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处于S1状态的磁阻电阻的自由层磁化方向；
步骤4：根据两个处于S1状态的磁阻电阻的给定参考层磁化方向、两个处于S1状态的隧穿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5：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处于S1状态的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 PCTCN2017090545-appb-000004
并再次执行步骤2～步骤5，直到两次结果的差值小于设定值。
进一步，步骤2中，计算两个处于S1状态的磁阻电阻的自由层磁化方向和参考层磁化方向的夹角的公式分别为：
Figure PCTCN2017090545-appb-000005
其中
Figure PCTCN2017090545-appb-000006
为第一个处于S1状态的磁阻电阻的自由层磁化方向，R1min为第一个处于S1状态的磁阻电阻的最小值，R1max为第一个处于S1状态的磁阻电阻的最大值；
Figure PCTCN2017090545-appb-000007
其中
Figure PCTCN2017090545-appb-000008
为第二个处于S1状态的磁阻电阻的自由层磁化方向，R2min为第二个处于S1状态的磁阻电阻的最小值，R2max为第二个处于S1状态的隧穿磁阻电阻的最大值。
进一步，步骤3中，根据公式计算两个处于S1状态的磁阻电阻的自由层磁化方向：
Figure PCTCN2017090545-appb-000009
将
Figure PCTCN2017090545-appb-000010
带入前式便得到第一处于S1状态的磁阻电阻 的自由层磁化方向
Figure PCTCN2017090545-appb-000011
将
Figure PCTCN2017090545-appb-000012
带入前式便得到第二处于S1状态的磁阻电阻的自由层磁化方向
Figure PCTCN2017090545-appb-000013
进一步，步骤4中利用下列方程组求解外加磁场的磁场幅值hF及方向θ：
Figure PCTCN2017090545-appb-000014
式中α1，α2分别为两个处于S1状态的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为磁阻电阻的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。
进一步，步骤5中，更新两个处于S1状态的磁阻电阻的参考层磁化方向
Figure PCTCN2017090545-appb-000015
Figure PCTCN2017090545-appb-000016
的步骤进一步包括：
求解一元四次方程
Figure PCTCN2017090545-appb-000017
其中hX1，hY1分别为外加磁场在第一处于S1状态的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 PCTCN2017090545-appb-000018
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 PCTCN2017090545-appb-000019
只有一个解，该解取决于3个条件：
1)x1为实数且|x1|≤1；
2)
Figure PCTCN2017090545-appb-000020
3)该解与磁阻电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 PCTCN2017090545-appb-000021
其中hX2，hY2分别为外加磁场在第二处于S1状态的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：hX2＝hFsinθ，hY2＝hFcosθ；
Figure PCTCN2017090545-appb-000022
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 PCTCN2017090545-appb-000023
只有一个解，该解取决于3个条件：
1)x2为实数且|x2|≤1；
2)
Figure PCTCN2017090545-appb-000024
3)该解与磁阻电阻的初始位置间所有角度能量必须小于初始位置的能量；
将求解得到的
Figure PCTCN2017090545-appb-000025
值分别作为新的给定的参考层磁化方向
Figure PCTCN2017090545-appb-000026
综上所述，由于采用了上述技术方案，本发明的有益效果是：
本发明提供的中大磁场测量方法实现了对中大磁场的准确测量，扩大了隧穿磁阻电阻的磁场强度测量范围。
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为本发明方法流程图。
图2为隧穿磁阻电阻的单畴行为的归一化星形曲线示意图。
图3为采用两个磁阻电阻测量磁场时测量范围随被测磁场强度角度变化的仿真图。
图4为本发明另一个实施例中四个磁阻电阻布设的结构示意图。
图5为采用四个磁阻电阻测量磁场时测量范围随被测磁场强度角度变化的仿真图。
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。
本发明方法适用于隧穿磁阻电阻、巨磁阻电阻等磁阻电阻，本实施例以隧 穿磁阻电阻为例进行说明。
如图1，本发明方法一个实施例的步骤包括：
(1)对于任一外加磁场，测量得到两个不同易轴方向的隧穿磁阻电阻R1，R2，同时将无磁场时的初始参考层磁化方向作为给定方向
Figure PCTCN2017090545-appb-000027
需要说明的是隧穿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。
若隧穿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。
隧穿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隧穿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 PCTCN2017090545-appb-000028
对应如图1过程①，计算公式为：
Figure PCTCN2017090545-appb-000029
其中
Figure PCTCN2017090545-appb-000030
为第一个隧穿磁阻电阻的自由层磁化方向，R1min为第一个隧穿磁阻电阻的最小值，R1max为第一个隧穿磁阻电阻的最大值。
Figure PCTCN2017090545-appb-000031
其中
Figure PCTCN2017090545-appb-000032
为第二个隧穿磁阻电阻的自由层磁化方向，R2min为第二个隧穿磁阻电阻的最小值，R2max为第二个隧穿磁阻电阻的最大值。
R1min、R1max、R2min及R2max均可通过分别标定两个隧穿磁阻电阻得到。
(3)对于给定的参考层磁化方向，计算自由层磁化方向
Figure PCTCN2017090545-appb-000033
如图1过程②，计算公式为
Figure PCTCN2017090545-appb-000034
将
Figure PCTCN2017090545-appb-000035
带入前式便得到第一隧穿磁阻电阻的自由层磁化方向
Figure PCTCN2017090545-appb-000036
将
Figure PCTCN2017090545-appb-000037
带入前式便得到第二隧穿磁阻电阻的自由层磁化方向
Figure PCTCN2017090545-appb-000038
式中，S1，S2分别表示自由层磁畴处于图2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。
(4)根据计算得到的自由层磁化方向
Figure PCTCN2017090545-appb-000039
计算被测磁场幅值和方向hF，θ，如图1过程③，计算公式为式：
Figure PCTCN2017090545-appb-000040
式中，式中α1，α2分别为两个隧穿磁阻电阻的易轴方向，hJFR为任一个隧穿磁阻电阻的自由层与参考层的耦合场，hBF＝HBF/HAF，HBF为隧穿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。当各隧穿磁阻电阻相同时，我们认为其内部的固有参数是相同的。
(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 PCTCN2017090545-appb-000041
如图示过程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 PCTCN2017090545-appb-000042
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 PCTCN2017090545-appb-000043
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 PCTCN2017090545-appb-000044
只有一个解。该解取决于3个条件：
1)x1为实数且|x1|≤1；
2)
Figure PCTCN2017090545-appb-000045
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 PCTCN2017090545-appb-000046
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 PCTCN2017090545-appb-000047
与
Figure PCTCN2017090545-appb-000048
的筛选过程同理，确定
Figure PCTCN2017090545-appb-000049
将求解得到的
Figure PCTCN2017090545-appb-000050
值分别作为新的给定的参考层磁化方向
Figure PCTCN2017090545-appb-000051
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 PCTCN2017090545-appb-000052
的解：
Figure PCTCN2017090545-appb-000053
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 PCTCN2017090545-appb-000054
上式可演化为：
Figure PCTCN2017090545-appb-000055
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。
图3为采用本实施例测量磁场时，磁场方向测量范围随被测磁场不同角度的测量范围仿真。可以看到当被测处于0～90°时，两个磁阻电阻自由层始终处于S1状态，不会发生磁畴不可逆旋转，因此迭代算法中的步骤(3)使用的公式确定为S1状态时的值，从而具有较大的测量范围；而当被测磁场处于90°～360°时，磁畴可能发生不可逆旋转，此时磁阻电阻的自由层状态不确定，也无法事先确定芯片自由层状态。若迭代算法中的步骤(3)使用的公式固定为S1状态时的值，当磁场较小时，芯片自由层仍处于S1状态，迭代算法有效；而当磁场较大时，由于磁畴发生不可逆旋转，最后迭代算法收敛到错误值或不收敛。因此在只有两个芯片的情况下，被测磁场为90°～360°时的测量范围取决于自由层内部偏置场到星形曲线的距离，此时磁畴旋转可逆连续。通常自由层的内部偏置场很小，其到星形曲线的距离很短，因此90°～360°时的测量范围很小。
为了提前确定隧穿磁阻芯片的自由层状态，扩大90°～360°的测量范围，增加另两个正交布置的芯片R3、R4，四个芯片布置如图4。
当上述四个隧穿磁阻自由层的内部易轴偏置磁场大于各向异性场(hBXF>1)时，总至少有两个隧穿磁阻自由层处于S1状态，朝向各自的易轴正方向，从而可以利用这两个电阻进行迭代计算，得到较大的测量范围。而制作自由层的内部易轴偏置磁场大于各向异性场的隧穿磁阻电阻又是本领域技术人员可以实现的。同时被测磁场朝向难轴负方向的两个隧穿磁阻电阻最小，通过这两个 电阻即可确定处于S1状态的两个电阻。如图5所示，相对于R2和R3的易轴方向，被测磁场趋向其难轴负方向，这两个电阻值最低，而相对于R1和R2的易轴方向，被测磁场趋向其易轴正方向，且位于星形曲线外，其磁畴状态肯定趋向易轴正方向，处于S1状态。
对此，先测量四个电阻的阻值，找出其中阻值最小的两个电阻，然后可以确定另外两个电阻处理S1状态，进而将处理S1状态的两个电阻值带入前述的步骤中进行迭代计算，从而得到待测磁场的强度及方向。
图6示出了采用四个磁阻电阻测量磁场的测量范围随被测磁场方向变化的仿真图。与图3相对，采用四个磁阻电阻测量外界磁场，当外界磁场的方向为90°～360°范围时，也能获取较大的测量范围。
图7展示的是当四个磁阻电阻如图4那样布设时，在不同的被测磁场方向下与各个磁阻电阻的状态。在实际运用中，无需严格参照本表格，只需要根据实际测量到的电阻的阻值便能确定处于S1状态的两个磁阻电阻。
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 (5)

  1. 一种中大磁场全象限测量方法，其特征在于，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；其中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；四个磁阻电阻自由层的内部易轴偏置磁场大于各向异性场；
    步骤2：确定最小阻值的两个磁阻电阻，进而确定另外两个磁阻电阻处于S1状态，并令处于S1状态的两个磁阻电阻的阻值为R1，R2，同时将无磁场时处于S1状态的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 PCTCN2017090545-appb-100001
    S1状态是指磁阻电阻的自由层磁畴处于易轴正方向；
    步骤2：根据阻值R1，R2分别计算两个处于S1状态的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3：分别根据两个处于S1状态的磁阻电阻的给定参考层磁化方向
    Figure PCTCN2017090545-appb-100002
    Figure PCTCN2017090545-appb-100003
    及两个处于S1状态的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处于S1状态的磁阻电阻的自由层磁化方向；
    步骤4：根据两个处于S1状态的磁阻电阻的给定参考层磁化方向、两个处于S1状态的隧穿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5：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处于S1状态的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 PCTCN2017090545-appb-100004
    并再次执行步骤2～步骤5，直到两次结果的差值小于设定值。
  2. 根据权利要求1所述的一种中大磁场全象限测量方法，其特征在于，步骤2中，计算两个处于S1状态的磁阻电阻的自由层磁化方向和参考层磁化方向的夹角的公式分别为：
    Figure PCTCN2017090545-appb-100005
    其中
    Figure PCTCN2017090545-appb-100006
    为第一个处于S1状态的磁阻电阻的自由层磁化方向，R1min为第一个处于S1状态的磁阻电阻的最小值，R1max为第一个处于S1状态的磁阻电阻的最大值；
    Figure PCTCN2017090545-appb-100007
    其中
    Figure PCTCN2017090545-appb-100008
    为第二个处于S1状态的磁阻电阻的自由层磁化方向，R2min为第二个处于S1状态的磁阻电阻的最小值，R2max为第二个处于S1状态的隧穿磁阻电阻的最大值。
  3. 根据权利要求1所述的一种中大磁场全象限测量方法，其特征在于，步骤3中，根据公式计算两个处于S1状态的磁阻电阻的自由层磁化方向：
    Figure PCTCN2017090545-appb-100009
    将
    Figure PCTCN2017090545-appb-100010
    带入前式便得到第一处于S1状态的磁阻电阻的自由层磁化方向
    Figure PCTCN2017090545-appb-100011
    将
    Figure PCTCN2017090545-appb-100012
    带入前式便得到第二处于S1状态的磁阻电阻的自由层磁化方向
    Figure PCTCN2017090545-appb-100013
  4. 根据权利要求1所述的一种中大磁场全象限测量方法，其特征在于，步骤4中利用下列方程组求解外加磁场的磁场幅值hF及方向θ：
    Figure PCTCN2017090545-appb-100014
    式中α1，α2分别为两个处于S1状态的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为磁阻电阻的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。
  5. 根据权利要求1所述的一种中大磁场全象限测量方法，其特征在于，步骤5中，更新两个处于S1状态的磁阻电阻的参考层磁化方向
    Figure PCTCN2017090545-appb-100015
    的步骤进一步包括：
    求解一元四次方程
    Figure PCTCN2017090545-appb-100016
    其中hX1，hY1分别为外加磁场在第一处于S1状态的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 PCTCN2017090545-appb-100017
    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 PCTCN2017090545-appb-100018
    只有一个解，该解取决于3个条件：
    1)x1为实数且|x1|≤1；
    2)
    Figure PCTCN2017090545-appb-100019
    3)该解与磁阻电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 PCTCN2017090545-appb-100020
    其中hX2，hY2分别为外加磁场在第二处于S1状态的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：hX2＝hFsinθ，hY2＝hFcosθ；
    Figure PCTCN2017090545-appb-100021
    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 PCTCN2017090545-appb-100022
    只有一个解，该解取决于3个条件：
    1)x2为实数且|x2|≤1；
    2)
    Figure PCTCN2017090545-appb-100023
    3)该解与磁阻电阻的初始位置间所有角度能量必须小于初始位置的能量；
    将求解得到的
    Figure PCTCN2017090545-appb-100024
    值分别作为新的给定的参考层磁化方向
    Figure PCTCN2017090545-appb-100025
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