JP2016114408A - Magnetic field detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field detection device that can be driven at a relatively high frequency, has a simple circuit configuration, and is capable of detecting external magnetic fields with high sensitivity.SOLUTION: A first variable resistance unit R1, second variable resistance unit R2, third variable resistance unit R3, and fourth variable resistance unit R4 constitute a full bridge circuit. Each variable resistance unit R1, R2, R3, R4 comprises magnetoresistive effect elements 10 and current paths 21, 22, 23, 24 that are serially connected and parallelly positioned to face each other. When AC voltage Vdd is applied, magnetic fields H1, H2, H3, H4 induced by current I1, I2,I3, I4 flowing through the current paths 21, 22, 23, 24 acts on the magnetoresistive effect elements 10. The full bridge circuit generates an output that is a composite of resistance variation due to the current-induced magnetic fields H1, H2, H3, H4 and resistance variation due to external magnetic fields.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fluxgate type magnetic field detection device, and more particularly to a magnetic field detection device that can be operated with a simple circuit configuration and can detect an external magnetic field with high sensitivity.

  For example, a magnetic field detection device that detects a weak external magnetic field such as geomagnetism uses a GMR element (giant magnetoresistive effect element). However, in the structure in which the external magnetic field is directly detected by the GMR element, improvement in detection sensitivity is limited. Further, the magnetic field detection output by the GMR element has hysteresis and has a drawback that an offset is likely to occur.

  Therefore, a fluxgate type magnetic field detection device has been developed. The flux type magnetic field detection device measures a change in the resistance value of the GMR element while applying an alternating magnetic field to the GMR element at the time of measurement. When an external magnetic field is applied, the GMR element exhibits a resistance change in which a resistance change due to the application of the alternating magnetic field and a resistance change due to the application of the external magnetic field are combined. By obtaining the output fluctuation amount based on this resistance change, the resistance change component based on the external magnetic field is obtained.

  The flux gate type magnetic field detection device has an advantage of less influence of hysteresis and offset. However, in order to detect a weak external magnetic field with high sensitivity, it is necessary to use a GMR element having a small saturation magnetic field and to increase the frequency of the alternating magnetic field. However, in the structure in which the winding coil is energized to generate the alternating magnetic field, the inductance becomes high, so if the frequency of the alternating current is increased, the generated magnetic field is likely to be delayed or fluctuated due to the time constant. Detection accuracy decreases.

The following Patent Document 1 describes an invention of a method for measuring a weak magnetic field.
In the present invention, a drive strap is provided on a magnetoresistive sensor so that an AC drive current is applied to the drive strap, and a current magnetic field from the drive strap becomes an AC magnetic drive magnetization. Given. At this time, the component of the external magnetic field is calculated from the output obtained from the resistance magnetic sensor.

JP 2013-137301 A

  In the method described in Patent Document 1, AC magnetic drive magnetization is given to the magnetoresistive sensor from the drive strap formed on the magnetoresistive sensor, so that the size can be reduced and a coil having a large number of turns is used. Therefore, the inductance of the drive strap can be made relatively small.

  However, in the method described in Patent Document 1, an AC drive current is generated and applied to the drive strap by a frequency generator and a frequency divider in a path different from that for supplying a detection current to the magnetoresistive sensor. Yes. In this method, it is necessary to apply the reference signal generated by the frequency generator to the phase sensitive sensor and process the sensing voltage obtained from the magnetoresistive sensor in synchronization with the reference signal. The circuit structure for detecting the external magnetic field is complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic field detection apparatus that can be configured in a small size, can reduce inductance, and can detect an external magnetic field with high accuracy with a simple circuit configuration.

The magnetic field detection device of the present invention includes a magnetoresistive effect element formed in an elongated shape, an energization path arranged in parallel with the magnetoresistive effect element and connected in series with the magnetoresistive effect element, and the energization path And a power supply unit that applies an alternating current to the magnetoresistive effect element, and a detection circuit unit that detects an output based on a resistance change of the magnetoresistive effect element,
The output is caused by a first output component caused by a current magnetic field induced by the current flowing through the current path acting on the magnetoresistive effect element and an external magnetic field acting on the magnetoresistive effect element. The second output component is synthesized, and the detection circuit obtains the second output component from the output.

  The magnetic field detection apparatus of the present invention is configured such that a threshold value is set in the detection circuit, and the second output component is obtained from a change in time when the output exceeds the threshold value.

The magnetic field detection apparatus of the present invention is provided with a first resistance change section and a second resistance change section having the magnetoresistive effect element and the energization path, and the first resistance change section and the second resistance change section. Are connected in series, and the conduction path and the magnetoresistive effect element of the first resistance change part and the conduction path and the magnetoresistive effect element of the second resistance change part are mutually connected. Arranged in parallel,
Each of the magnetoresistive effect elements is a GMR element having a fixed magnetic layer and a free magnetic layer, and the fixed magnetization direction of the fixed magnetic layer is determined by the first resistance change unit and the second resistance change unit. Are opposite directions, and the output can be obtained from the midpoint between the first resistance change portion and the second resistance change portion.

Further, the magnetic field detection device of the present invention is provided with a third resistance change section and a fourth resistance change section having the magnetoresistive effect element and the energization path, and the third resistance change section and the first resistance change section. 4 resistance change units are connected in series, and a series group of the first resistance change unit and the second resistance change unit, and the third resistance change unit and the fourth resistance change unit. The series group is connected in parallel to each other,
The energization path and the magnetoresistive effect element of the third resistance change unit and the energization path and the magnetoresistive effect element of the fourth resistance change unit are arranged in parallel to each other,
Each of the magnetoresistive effect elements is a GMR element having a fixed magnetic layer and a free magnetic layer, and the fixed magnetization direction of the fixed magnetic layer is determined by the first resistance change unit and the second resistance change unit. Are in the opposite direction, the first resistance change portion and the fourth resistance change portion have the same fixed magnetization direction, and the second resistance change portion and the third resistance change portion are fixed. The direction of magnetization is the same,
The output from the midpoint between the first resistance change section and the second resistance change section, and the output from the midpoint between the third resistance change section and the fourth resistance change section. Difference is required.

In the magnetic field detection apparatus of the present invention, the magnetoresistive effect element is a first magnetoresistive effect element, and the energization path is a second magnetoresistive effect element,
The current induced by the alternating current flowing through the first magnetoresistive effect element changes the resistance of the second magnetoresistive effect element due to the current magnetic field induced by the alternating current flowing through the first magnetoresistive effect element. The resistance of the first magnetoresistive element can be changed by a magnetic field.

  In this case, the first magnetoresistive effect element and the second magnetoresistive effect element are GMR elements, and the first magnetoresistive effect element and the second magnetoresistive effect connected in series with each other. The direction of the fixed magnetization of the fixed magnetic layer is the same for the element.

  In the magnetic field detection apparatus of the present invention, it is preferable that the fixed magnetization direction is orthogonal to the longitudinal direction of the magnetoresistive effect element.

  In the magnetic field detection device of the present invention, an alternating current is applied to the current-carrying path and the magnetoresistive effect element connected in series, and a current magnetic field is applied from the current flowing through the current-carrying path to the magnetoresistive effect element. An output based on the resistance change obtained by combining the change and the resistance change due to the external magnetic field is obtained. From this output, an output based on a resistance change due to an external magnetic field is extracted. According to the present invention, the inductance can be reduced and the frequency of the alternating current can be made relatively high, and the external magnetic field can be detected with high sensitivity as compared with the method in which a current magnetic field is applied to the magnetoresistive effect element from a coil having a large number of turns. become.

  This magnetic field detection device has a structure in which an alternating current, which is a drive current, is applied to both a current path and a magnetoresistive effect element connected in series, and an output obtained as a resistance change of the magnetoresistive effect element as in the conventional example The circuit configuration such as processing in synchronization with the frequency of the alternating current becomes unnecessary, and high-sensitivity detection with a simple structure becomes possible.

  In addition, by using a magnetoresistive element as the energization path, it is possible to obtain a magnetic field detection device that is more sensitive to a weak external magnetic field.

The top view which shows the magnetic field detection apparatus of the 1st Embodiment of this invention, 1 is a circuit diagram of the magnetic field detection device shown in FIG. Sectional drawing which shows the energization path and magnetoresistive effect element which comprise a 1st resistance change part, (A) is explanatory drawing which shows the structure and operation | movement of an electricity supply path and a magnetoresistive effect element which comprise a 1st resistance change part, (B) is an electricity supply path and a magnetoresistive effect which comprise a 2nd resistance change part. An explanatory diagram showing the structure and operation of the element, 1 shows a magnetic field detection apparatus according to a second embodiment of the present invention, in which (A) shows a current path (second magnetoresistive element) and a first magnetoresistance constituting a first resistance change section. Explanatory drawing which shows the structure and operation | movement of an effect element, (B) shows the structure and operation | movement of the electricity supply path (2nd magnetoresistive effect element) and 1st magnetoresistive effect element which comprise a 2nd resistance change part. Illustration, (A) is a diagram showing an alternating voltage applied to the magnetic field detection device of the first embodiment shown in FIG. 1, (B) is a diagram showing a differential output of outputs from two middle points,

  A magnetic field detection apparatus 1 according to the first embodiment shown in FIGS. 1 and 2 is configured by a thin film stack formed along an XY plane which is a surface of a substrate.

  The magnetic field detection device 1 includes a first resistance change unit R1, a second resistance change unit R2, a third resistance change unit R3, and a fourth resistance change unit R4.

  The first resistance change unit R1 and the second resistance change unit R2 are connected in series, and the third resistance change unit R3 and the fourth resistance change unit R4 are connected in series. A series group of the first resistance change unit R1 and the second resistance change unit R2 and a series group of the third resistance change unit R3 and the fourth resistance change unit R4 are connected in parallel. As shown in FIG. 2, the magnetic field detection device 1 is connected to a power supply unit 2 that applies an alternating current (alternating current power), and ends of the first resistance change unit R1 and the third resistance change unit on the Y1 side. An alternating voltage (AC voltage: drive voltage) Vdd is applied to the Y2 side end of the second resistance change unit R2 and the Y2 side end of the fourth resistance change unit R4 to the ground potential Gnd. Is set.

  The first midpoint output Out1 is obtained from the midpoint between the first resistance change portion R1 and the second resistance change portion R2, and the midpoint between the third resistance change portion R3 and the fourth resistance change portion R4. From the second midpoint output Out2. As shown in FIG. 2, the first midpoint output Out1 and the second midpoint output Out2 are provided to the differential amplifier 3, and the first midpoint output Out1 and the second midpoint output Out2 are Difference is required. The differential output from the differential amplifier 3 is given to the threshold value setting unit 4 to obtain a detection output Out whose waveform has been shaped. This detection output Out is given to the low-pass filter 5, and this output reflects the change of the external magnetic field B. Further, preferably, the output adjustment unit 6 adjusts the output to a necessary size.

  As shown in FIG. 1, each of the first resistance change unit R1, the second resistance change unit R2, the third resistance change unit R3, and the fourth resistance change unit R4 includes a plurality of magnetoresistive effect elements 10. All of the magnetoresistive effect elements 10 have a long shape whose longitudinal direction is directed in the left-right direction (X direction) and are formed in parallel to each other.

  A plurality of energization paths 21 are formed in the first resistance change portion R1. Each energization path 21 has a long shape whose longitudinal direction is directed in the left-right direction (X direction). Similarly, in the second resistance change portion R2, the third resistance change portion R3, and the fourth resistance change portion R4, there are long current paths 22, 23, 24 whose longitudinal directions are directed in the X direction. Is formed.

  FIG. 4A shows a part of the magnetoresistive effect element 10 and the energization path 21 arranged in the first resistance change portion R1. As shown in FIG. 1, in the first resistance change portion R1, the end on the X1 side of the magnetoresistive effect element 10 in which the end portion on the X1 side of each energization path 21 is located below the connecting portion 26a is provided. Connected to the department. In addition, the end portion on the X2 side of each energization path 21 is connected to the end portion on the X2 side of the magnetoresistive effect element 10 adjacent to the Y1 side via the connection portion 26b. Therefore, in each row of the meander pattern of the first resistance change portion R1, the energization path 21 and the magnetoresistive effect element 10 are connected in series and turned back at the connection portion 26a to face each other in parallel. ing.

  FIG. 6A shows a change in the alternating voltage (drive voltage) generated by the power supply unit 2. The alternating voltage changes with a waveform approximating a trigonometric function, but the change region is on the positive potential side and does not cross 0 volts. Therefore, the alternating current (drive current) I1 flowing through each energization path 21 of the first resistance change unit R1 is always directed in the X1 direction. The alternating current Ia flowing through each magnetoresistive effect element 10 is directed in the X2 direction.

  FIG. 4B shows a part of the magnetoresistive effect element 10 and the energization path 22 arranged in the second resistance change portion R2. As shown in FIG. 1, the end portion on the X2 side of the energization path 22 is connected to the end portion on the X2 side of the magnetoresistive effect element 10 located thereunder via a connection portion 27b, and the X1 side of the energization path 22 Is connected to the X1 end of the magnetoresistive effect element 10 adjacent to the Y2 side via a connecting portion 27a. Also in the second resistance change portion R2, the energization path 22 and the magnetoresistive effect element 10 are connected in series and turned back at the connection portion 27b, and face each other in parallel.

  Also in the second resistance change portion R2, the alternating current I2 flows in the X1 direction through the respective conduction paths 22 arranged in the meander pattern, and the alternating current Ib flows in the X2 direction through the magnetoresistive effect element 10.

  As shown in FIG. 1, the connection structure between the magnetoresistive effect element 10 and the current path 23 or 24 in the third resistance change portion R3 and the fourth resistance change portion R4 is substantially the same as that of the second resistance change portion R2. The same. Also in the third resistance change portion R3, the alternating current I3 flows in the X1 direction in each energization path 23, and the alternating current flows in the X2 direction in the magnetoresistive effect element 10. Similarly, also in the fourth resistance change portion R4, the alternating current I4 flows in the X1 direction in each energization path 24, and the alternating current flows in the X2 direction in the magnetoresistive effect element 10.

  FIG. 3 is a cross-sectional view showing a laminated structure of the magnetoresistive effect elements 10 and the current paths 21 arranged in the first resistance change portion R1.

  The magnetoresistive effect element 10 is a giant magnetoresistive effect element (GMR element), and an insulating underlayer 8 and a seed layer 9 are formed on a substrate 7, and a fixed magnetic layer 11 and a nonmagnetic layer are formed thereon. 12 and a free magnetic layer 13 are sequentially laminated, and the free magnetic layer 13 is covered with a protective layer and an insulating layer 14.

  The pinned magnetic layer 11 has a laminated ferrimagnetic structure including a first pinned layer 11a and a second pinned layer 21b, and a nonmagnetic intermediate layer 11c located between the first pinned layer 11a and the second pinned layer 11b. It is. The first fixed layer 11a and the second fixed layer 11b are formed of a soft magnetic material such as a CoFe alloy (cobalt-iron alloy). The nonmagnetic intermediate layer 11c is made of Ru (ruthenium) or the like.

  The pinned magnetic layer 11 having a laminated ferrimagnetic structure has a so-called self-pinned structure in which the magnetizations of the first pinned layer 11a and the second pinned layer 11b are pinned antiparallel. The pinned magnetic layer 11 having the laminated ferrimagnetic structure has its magnetization direction fixed by antiferromagnetic coupling between the first pinned layer 11a and the second pinned layer 11b without performing heat treatment in the magnetization. The direction of pinned magnetization of the pinned magnetic layer 11 is the direction of magnetization of the second pinned layer 11b. In the first resistance change unit R1, the direction of the fixed magnetization Pin of the fixed magnetic layer 11 of all the magnetoresistive effect elements 10 is the Y2 direction.

  The nonmagnetic layer 12 is formed of a nonmagnetic conductive material such as Cu (copper). The free magnetic layer 13 is formed of a soft magnetic material such as a NiFe alloy (nickel-iron alloy). The free magnetic layer 13 has a length in the left-right direction (X direction) that is sufficiently larger than a width dimension in the front-rear direction (Y direction). It is aligned.

  A protective layer and an insulating layer 14 are formed on the magnetoresistive element 10, and a current path 21 is formed thereon. A part of the protective layer and the insulating layer 14 is removed, and this removed portion is filled with the same conductive material as that of the energization path 21 to form connection portions 26 a and 26 b that are electrically connected to the magnetoresistive effect element 10.

  The current path 21 is formed of a nonmagnetic conductive material such as Al (aluminum), Cu, Ti (titanium), or Cr (chromium), and has, for example, a laminated structure of Cu and Al. The current path 21 is formed by a sputtering process or the like.

  In the magnetoresistive effect element 10, the Y direction, which is the direction of the fixed magnetization Pin of the fixed magnetic layer 11, is the sensitivity axis direction. When the magnetization aligned in the X direction in the free magnetic layer 13 is directed in the Y2 direction, which is parallel to the fixed magnetization Pin, the resistance value of the magnetoresistive element 10 becomes minimum, and the magnetization is antiparallel to the fixed magnetization Pin. When directed in the Y1 direction, the resistance value of the magnetoresistive element 10 becomes maximum.

  The structure of the magnetoresistive effect element 10 in the second resistance change portion R2, the third resistance change portion R3, and the fourth resistance change portion R4 and the stacked structure of the current paths 22, 23, or 24 are the first resistance change. It is substantially the same as the part R1. However, the direction of magnetization of the pinned magnetic layer 11 is different between the resistance change portions R1, R2, R3, and R4. The first resistance change unit R1 and the fourth resistance change unit R4 have the fixed magnetization Pin in the Y2 direction, and the second resistance change unit R2 and the third resistance change unit R3 have the fixed magnetization Pin in the Y1 direction. Direction.

Next, the operation of the magnetic field detection apparatus 1 according to the first embodiment will be described.
In the power supply unit 2, an alternating voltage (AC voltage: drive voltage) shown in FIG. 6A is generated. Since this voltage changes in the positive potential region, the energization path 21 of the first resistance change unit R1, the energization path 22 of the second resistance change unit R2, the energization path 23 of the third resistance change unit R3, and the fourth A current in the X1 direction always flows through the energization path 24 of the resistance change portion R4. The waveform change of the alternating voltage shown in FIG. 6A approximates a trigonometric function, but this waveform change may be a triangular wave (sawtooth wave) shape.

  As shown in FIG. 4A, in the first resistance change unit R1, a current magnetic field H1 is formed by an alternating current (alternating current: driving current) I1 flowing through the energizing path 21. Although the current magnetic field H1 is in the direction indicated by the arrow, the intensity of the current magnetic field H1 changes substantially based on the waveform of the trigonometric function according to the change in the alternating voltage shown in FIG. This current magnetic field H1 acts on the magnetoresistive effect element 10 in the Y2 direction, that is, in the same direction as the fixed magnetization Pin of the fixed magnetic layer 11.

  As shown in FIG. 4B, also in the second resistance change portion R2, an alternating current I2 flows in the X1 direction through the conduction path 22, and the current magnetic field H2 is applied to the magnetoresistive effect element 10 in the Y2 direction. It is done. In the second resistance change unit R2, the direction of the current magnetic field H2 applied to the magnetoresistive effect element 10 is opposite to the direction of the fixed magnetization Pin of the fixed magnetic layer 11.

  Similarly, a current magnetic field H3 in the Y2 direction is applied to the magnetoresistive effect element 10 of the third resistance change unit R3, and a current magnetic field in the Y2 direction is also applied to the magnetoresistive effect element 10 of the fourth resistance change unit R4. H4 is given. In the third resistance change unit R3, the direction of the current magnetic field H3 is opposite to the direction of the fixed magnetization Pin of the magnetoresistive effect element 10, and in the fourth resistance change unit R4, the direction of the current magnetic field H4 is the fixed magnetization Pin. It is the same direction as

  In FIG. 1, electromagnetic fields H1, H2, H3, and H4 acting on the magnetoresistive effect element 10 are indicated by arrows pointing in the Y2 direction under the name of “self-inducing magnetic field”.

  In the first resistance change portion R1, the second resistance change portion R2, the third resistance change portion R3, and the fourth resistance change portion R4, current magnetic fields H1, H2, H3, H4 acting on the magnetoresistive effect element 10 Are the same in design (absolute value).

  In the first resistance change unit R1, the second resistance change unit R2, the third resistance change unit R3, and the fourth resistance change unit R4, current magnetic fields H1, H2, and Y2 in the Y2 direction with respect to the magnetoresistive effect element 10 H3 and H4 act, and the magnetic field intensity changes according to the frequency of the alternating voltage Vdd shown in FIG. Therefore, in each resistance change part R1, R2, R3, R4, the resistance value of the magnetoresistive effect element 10 changes according to the frequency of the said alternating voltage Vdd.

  However, the direction of the fixed magnetization Pin of the pinned magnetic layer 11 in the first resistance change unit R1 and the fourth resistance change unit R4, and the fixed magnetism in the second resistance change unit R2 and the third resistance change unit R3. The directions of the fixed magnetization Pin of the layer 11 are opposite to each other. Therefore, the phase of the resistance change in the first resistance change unit R1 and the fourth resistance change unit R4 is different from the phase of the resistance change in the second resistance change unit R2 and the third resistance change unit R3 by 180 degrees. To do.

  Alternating currents Ia, Ib, Ic, and Id always flow in the X2 direction through the magnetoresistive effect elements 10 of the resistance change portions R1, R2, R3, and R4, and at the same time, the magnetic fields are generated by the current magnetic fields H1, H2, H3, and H4. The resistance value of the resistance effect element 10 is changed at the same frequency as the alternating current. In the first midpoint output Out1 and the second midpoint output Out2, voltage changes caused by changes in the alternating currents Ia, Ib, Ic, and Id appear in phase with each other, but the current magnetic fields H1, H2, H3, The change in voltage caused by the change in resistance of the magnetoresistive effect element 10 due to H4 appears in opposite phase between the first midpoint output Out1 and the second midpoint output Out2.

  The first midpoint output Out1 and the second midpoint output Out2 are supplied to the differential amplifier 3 to obtain a differential output. In this differential output, changes in voltage caused by changes in the alternating currents Ia, Ib, Ic, and Id at the first midpoint output Out1 and the second midpoint output Out2 are cancelled. When the external magnetic field is ignored, only the voltage change due to the resistance change of the magnetoresistive effect element 10 due to the current magnetic fields H1, H2, H3, and H4 is obtained as the differential output.

  Here, as shown in FIG. 1, when the external magnetic field B directed in the Y1 direction or the Y2 direction acts on the magnetic field detection device 1, the resistance values of all the magnetoresistive effect elements 10 change, Thus, an output is obtained in which the voltage change caused by the resistance change of the magnetoresistive effect element 10 due to the current magnetic fields H1, H2, H3, and H4 and the voltage change caused by the resistance change caused by the external magnetic field B are combined.

FIG. 6 shows an example of a simulation result of the operation of the magnetic field detection device 1.
FIG. 6A is an example of an alternating voltage generated by the power supply unit 2, and FIG. 6B shows a differential output obtained by the differential amplifier 3 when the alternating voltage is applied.

  In FIG. 6B, the differential output when the external magnetic field B is “0” is indicated by a rhombus mark (Out Field = 0 [mT]), and the external magnetic field B of 1 mT acts in the Y2 direction. Differential output is indicated by a square mark (Out Field = 1 [mT]), and the differential change when an external magnetic field B of 1 mT acts in the Y1 direction is a triangular mark (Out Field = -1 [mT]) It is shown in

  As shown in FIG. 2, the differential output is input to the threshold setting unit 4. The threshold value setting unit 4 sets the first threshold value and the second threshold value shown in FIG. The first threshold value and the second threshold value are set such that the width from the midpoint of the peak-to-peak value of the differential output when the external magnetic field B is “0” is the same.

  When the external magnetic field B is “0”, the time during which the differential output (differential voltage) is higher than the first threshold is approximately equal to the time during which the differential output is lower than the second threshold. When the external magnetic field B of 1 mT acts in the Y2 direction, the resistances of the second resistance change unit R2 and the third resistance change unit R3 increase, and the differential output shifts to the plus side. At this time, T1> T2 between the time T1 when the differential output is higher than the first threshold and the time T2 when the differential output is lower than the second threshold. Conversely, when an external magnetic field B of 1 mT acts in the Y1 direction, T1 <T2. In the external magnetic field detector 6 shown in FIG. 2, the direction and magnitude of the external magnetic field B are detected based on the ratio between the times T1 and T2.

  The magnetic field detection device 1 causes an alternating magnetic field (driving magnetic field: driving magnetic field) to be generated in the magnetoresistive effect element 10 by a current magnetic field generated in the linear energization paths 21, 22, 23, and 24 arranged in parallel with the magnetoresistive effect element 10. A self-inducing magnetic field). Since the linear current paths 21, 22, 23, and 24 have a lower inductance than that of the winding coil, the alternating voltage (drive voltage) shown in FIG. 6A can be set to a relatively high frequency. Thus, the frequency of the differential output shown in FIG. 6B can be increased. The higher the frequency of the differential output, the higher the resolution when detecting the external magnetic field B. Therefore, it is possible to obtain a highly sensitive detection output even with a weak external magnetic field B.

  In addition, the magnetoresistive effect element 10 and the current paths 21, 22, 23, and 24 are connected in series at the resistance change portions R1, R2, R3, and R4. Therefore, the alternating current flowing through the resistance change portion by the alternating voltage shown in FIG. 6A acts as a drive current for generating a current magnetic field in the energization paths 21, 22, 23, and 24, and the magnetoresistive effect element 10 Then, it acts as a detection current for detecting a change in resistance value due to the current magnetic field and a change in resistance value due to the external magnetic field B. As a matter of course, since the phase of the drive current and the detection current are the same, the frequency and the differential output for generating the current magnetic field in the phase sensitive detector as in the method described in Patent Document 1. There is no need for complicated circuit processing to synchronize the sense voltage.

FIG. 5 shows a magnetic field detection apparatus 1A according to the second embodiment of the present invention.
FIG. 5A shows the magnetoresistive effect element 10 and the energizing path 21A that constitute the first resistance change portion R1. The energizing path 21 </ b> A is configured by a GMR element having the same stacked structure as the magnetoresistive effect element 10. Therefore, the magnetoresistive effect element 10 functions as a first magnetoresistive effect element, and the energizing path 21A functions as a second magnetoresistive effect element. The directions of the fixed magnetization Pins of the magnetoresistive element 10 and the fixed magnetic layer of the energization path 21A that is the second magnetoresistive element are both in the Y2 direction. The energizing path 21A and the magnetoresistive effect element 10 are connected in series by the connecting portion 26a, and are folded back 180 degrees to face each other in parallel. The connecting portion 26a is formed of a conductive material that does not constitute a GMR element.

  When the alternating current I1 flows through the energization path 21A, a current magnetic field (driving current) H1 generated by this current acts on the magnetoresistive effect element 10 in the Y2 direction. Further, the current magnetic field Ha generated by the alternating current Ia flowing through the magnetoresistive effect element 10 also becomes a drive magnetic field, and acts on the energizing path 21A as the second magnetoresistive effect element in the Y2 direction.

  As shown in FIG. 5B, also in the second resistance change portion R2, the energization path 22A is composed of a GMR element, and the magnetoresistive effect element 10 functions as the first magnetoresistive effect element. The electric path 22A functions as a second magnetoresistive element. The energizing path 22A and the magnetoresistive effect element 10 are connected in series via the connecting portion 27b and face each other in parallel. However, in both the conduction path 22A and the magnetoresistive effect element 10 as the second magnetoresistive effect element, the direction of the fixed magnetization Pin of the fixed magnetic layer is the Y1 direction.

  In FIG. 5B, the current magnetic field H1 based on the alternating current I2 flowing through the energizing path 22A acts in the Y2 direction on the magnetoresistive effect element 10 and is based on the alternating current Ib flowing through the magnetoresistive effect element 10. Hb acts in the Y2 direction on the energizing path 22A that is the second magnetoresistive element.

  Although not shown, in the third resistance change portion R3, an alternating current I3 in the X1 direction flows through the energizing path 23A that is the second magnetoresistive element, and an alternating current in the X2 direction flows through the magnetoresistive element 10 in the X2 direction. Current flows. In the fourth resistance change portion R4, an alternating current I4 in the X1 direction flows through the energizing path 23 that is the second magnetoresistive element, and an alternating current in the X2 direction flows through the magnetoresistive element 10. In the third resistance change unit R3, the direction of the fixed magnetization Pin of the current path 23A that is the magnetoresistive effect element 10 and the second magnetoresistance effect element is the Y1 direction, and in the fourth resistance change unit R4, the magnetoresistance effect R4 The direction of the fixed magnetization Pin of the fixed magnetic layer of the effect element 10 and the conduction path 24A which is the second magnetoresistance effect element is the Y2 direction.

  In the magnetic field detection device 1A of the second embodiment, the energization paths 21A, 21B, 21C, and 21D are GMR elements, and the magnetoresistive effect element is generated by the current magnetic fields Ha, Hb, Hc, and Hd from the magnetoresistive effect element 10. Similarly, the resistance changes in the same phase as 10, and the resistance also changes in the same phase as that of the magnetoresistive effect element 10 with respect to the external magnetic field B. In this magnetic field detection apparatus 1A, since the length of the magnetoresistive effect element can be doubled in the resistance change portions R1, R2, R3, and R4 as compared with the first embodiment, it is the same size as the first embodiment. If it is formed, the S / N ratio can be improved, and if the performance is the same as that of the first embodiment, the size can be made smaller than that of the first embodiment.

  In each of the above embodiments, the resistance change sections R1, R2, R3, and R4 form a full bridge circuit. However, a series circuit is formed by the first resistance change section R1 and the second resistance change section R2. You may comprise, and you may comprise a bridge circuit by making resistance change part R3, R4 into fixed resistance.

B External magnetic field H1, H2, H3, H4 Current magnetic field Ha, Hb Current magnetic field Ia, Ib, Ic, Id Alternating current Out Detection output Out1 First midpoint output Out2 Second midpoint output Pin Fixed magnetization R1 First Resistance change portion R2 Second resistance change portion R3 Third resistance change portion R4 Fourth resistance change portion Vdd Alternating voltage (drive voltage)
DESCRIPTION OF SYMBOLS 1,1A Magnetic field detection apparatus 2 Power supply part 3 Differential amplification part 4 Threshold setting part 5 Low pass filter 6 Output adjustment part 10 Magnetoresistive element 11 Fixed magnetic layer 12 Nonmagnetic layer 13 Free magnetic layers 21, 22, 23, 24 Current path 21A, 22A, 23A, 24A Current path (second magnetoresistive element)

Claims (7)

A magnetoresistive effect element formed in a long shape, an energizing path arranged in parallel with the magnetoresistive effect element and connected in series with the magnetoresistive effect element, and alternating between the energizing path and the magnetoresistive effect element A power supply unit for supplying a current, and a detection circuit unit for detecting an output based on a resistance change of the magnetoresistive element;
The output is caused by a first output component caused by a current magnetic field induced by the current flowing through the current path acting on the magnetoresistive effect element and an external magnetic field acting on the magnetoresistive effect element. And the second output component to be combined,
In the detection circuit, the second output component is obtained from the output.   The magnetic field detection device according to claim 1, wherein a threshold value is set in the detection circuit, and the second output component is obtained from a change in time when the output exceeds the threshold value. A first resistance change portion and a second resistance change portion having the magnetoresistive effect element and the energization path are provided, and the first resistance change portion and the second resistance change portion are connected in series. The conduction path and the magnetoresistive effect element of the first resistance change unit and the conduction path and the magnetoresistive effect element of the second resistance change unit are arranged in parallel with each other,
Each of the magnetoresistive effect elements is a GMR element having a fixed magnetic layer and a free magnetic layer, and the fixed magnetization direction of the fixed magnetic layer is determined by the first resistance change unit and the second resistance change unit. The magnetic field detection apparatus according to claim 1, wherein the output is obtained from a middle point between the first resistance change unit and the second resistance change unit. A third resistance change section and a fourth resistance change section having the magnetoresistive effect element and the energization path are provided, and the third resistance change section and the fourth resistance change section are connected in series. A series group of the first resistance change unit and the second resistance change unit, and a series group of the third resistance change unit and the fourth resistance change unit are connected in parallel to each other. ,
The energization path and the magnetoresistive effect element of the third resistance change unit and the energization path and the magnetoresistive effect element of the fourth resistance change unit are arranged in parallel to each other,
Each of the magnetoresistive effect elements is a GMR element having a fixed magnetic layer and a free magnetic layer, and the fixed magnetization direction of the fixed magnetic layer is determined by the first resistance change unit and the second resistance change unit. Are in the opposite direction, the first resistance change portion and the fourth resistance change portion have the same fixed magnetization direction, and the second resistance change portion and the third resistance change portion are fixed. The direction of magnetization is the same,
The output from the midpoint between the first resistance change section and the second resistance change section, and the output from the midpoint between the third resistance change section and the fourth resistance change section. The magnetic field detection apparatus according to claim 3, wherein the difference is obtained. The magnetoresistive effect element is a first magnetoresistive effect element, and the energization path is a second magnetoresistive effect element;
The current induced by the alternating current flowing through the first magnetoresistive effect element changes the resistance of the second magnetoresistive effect element due to the current magnetic field induced by the alternating current flowing through the first magnetoresistive effect element. The magnetic field detection device according to claim 1, wherein a resistance of the first magnetoresistive element is changed by a magnetic field.   The first magnetoresistance effect element and the second magnetoresistance effect element are GMR elements, and the first magnetoresistance effect element and the second magnetoresistance effect element connected in series with each other, The magnetic field detection device according to claim 5, wherein the fixed magnetization layers have the same fixed magnetization direction.   The magnetic field detection device according to claim 3, wherein a direction of the fixed magnetization is orthogonal to a longitudinal direction of the magnetoresistive element.