JP6617156B2 - Magnetic field detector - Google Patents

Description

  The present invention relates to a so-called magnetic field balance type magnetic sensing device using a coil for providing a feedback magnetic field.

  Patent Document 1 discloses an invention relating to a so-called magnetic field balance type current sensor as a magnetic detection device.

  In this current sensor, a magnetoresistive element and a feedback coil are opposed to a conductor through which a current to be measured passes. The magnetic field excited by the current to be measured flowing through the conductor is detected by the magnetoresistive effect element, and a feedback current corresponding to the magnitude of the detected output is controlled to be applied to the feedback coil. A feedback magnetic field (cancellation magnetic field) opposite to the current magnetic field is applied from the feedback coil to the magnetoresistive effect element, and the current flowing in the feedback coil when the current magnetic field and the feedback magnetic field are in an equilibrium state. Is detected, and the current detection output becomes the measured value of the current to be measured.

  In the current sensor, four magnetoresistive elements are arranged along the direction of the current to be measured flowing through the conductor. The four magnetoresistive elements are GMR elements in which a ferromagnetic pinned layer and a soft magnetic free layer are stacked with a nonmagnetic intermediate layer interposed therebetween. The Pin direction, which is the magnetization direction of the ferromagnetic pinned layers of the two magnetoresistive effect elements, and the Pin direction of the ferromagnetic pinned layers of the other two magnetoresistive effect elements are opposite to each other by 180 degrees. The direction is perpendicular to the direction of the current to be measured.

  Then, two magnetoresistive effect elements whose Pin directions are opposite to each other are connected in series, and two sets of the series parts are connected in parallel to form a bridge circuit. In this bridge circuit, when a current magnetic field is applied, the resistance values of magnetoresistive elements having different Pin directions change in reverse polarity. Therefore, by obtaining the difference between the output Out1 of the midpoint of the two magnetoresistive elements in one series part and the output Out2 of the midpoint of the two magnetoresistive elements in the other series part, The intensity of the current magnetic field can be detected.

  The magnetic balance type current sensor described in Patent Document 2 is provided with two sensor elements A and B across a conductor through which a current to be measured passes. Each of the two sensor elements A and B has the same structure as the current sensor described in Patent Document 1, and each of the two sensor elements A and B includes four magnetoresistive elements and a feedback coil. have.

  The magnetic balance type current sensor described in Patent Document 2 is designed to cancel an error due to a temperature rise and maintain high linearity by taking a differential of outputs of two sensor elements A and B. .

WO2011-111493 WO2011 / 043193

  Each of the current sensor described in Patent Document 1 and the two sensor elements A and B described in Patent Document 2 has four magnetoresistive elements in the direction in which the current to be measured flows in the conductor. The four magnetoresistive elements are arranged opposite to each cancel coil.

  As described above, in order to configure a bridge circuit with four magnetoresistive elements, the pinned direction of the ferromagnetic pinned layer is changed between the two magnetoresistive elements and the other two magnetoresistive elements. , They need to be 180 degrees opposite to each other.

  If the pinned direction of the ferromagnetic pinned layer is determined by antiferromagnetic coupling using the antiferromagnetic layer, it is necessary to anneal the magnetic pinned layer and the antiferromagnetic layer in a magnetic field after being laminated. . Therefore, it is difficult to set the pinned direction of the ferromagnetic fixed layer in the reverse direction with a plurality of magnetoresistive elements formed on the same substrate. Therefore, in order to make the pin direction of the pinned magnetic layer of the four magnetoresistive elements provided side by side in one current sensor determined by antiferromagnetic coupling, magnetoresistive elements having different Pin directions are different. It is necessary to form two each on the substrate and separately incorporate two magnetoresistive elements into the current sensor. However, in this case, since two types of boards are incorporated in one current sensor, the assembly process and the wiring process become complicated.

  In this regard, the magnetoresistive effect element described in Patent Document 1 and Patent Document 2 is a so-called self-locking type strong element in which a first ferromagnetic layer and a second ferromagnetic layer are stacked via an antiparallel coupling film. A magnetic pinned layer is used. This ferromagnetic pinned layer can be formed by a film-forming process in a magnetic field and does not require an annealing process. Therefore, it is possible to form a magnetoresistive element having a reverse Pin direction on a common substrate.

  However, the self-stopping ferromagnetic pinned layer has a drawback that the Pin direction changes when strong external magnetization acts. If it is used in a strong magnetic field, the sensitivity is reduced and the offset output is superimposed on the detection output. In addition, problems such as fluctuations in offset output are likely to occur.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a magnetic field detection device that can be configured to align the magnetization directions of the pinned magnetic layers of the magnetoresistive effect element facing one coil.

  Another object of the present invention is to provide a magnetic field detection device that can increase sensitivity and expand a dynamic range by using two coils.

The present invention relates to a magnetic detection unit whose detection output changes according to the intensity of the measurement magnetic field, a coil that applies a feedback magnetic field opposite to the measurement magnetic field to the magnetic detection unit, and a detection output of the magnetic detection unit In the magnetic field detection device provided with a coil energization unit that supplies a feedback current for inducing the feedback magnetic field to the coil, and a detection unit that detects an amount of current flowing in the coil,
A first detection unit and a second detection unit are provided, and the first detection unit includes a first magnetic detection unit and a first coil that applies the feedback magnetic field to the first magnetic detection unit. Provided, the second detection unit is provided with a second magnetic detection unit, and a second coil that applies the feedback magnetic field to the second magnetic detection unit,
The first magnetic detection unit and the second magnetic detection unit each include at least two magnetoresistive effect elements whose resistance values change according to the magnetization directions of the free magnetic layer and the pinned magnetic layer,
The at least two magnetoresistive elements provided in the first magnetic detection unit have the same fixed magnetization direction of the fixed magnetic layer, and at least two magnetoresistive elements provided in the second magnetic detection unit. The magnetoresistive element has the same fixed magnetization direction of the fixed magnetic layer,
One of the fixed magnetization direction of the magnetoresistive effect element provided in the first magnetic detection unit and the fixed magnetization direction of the magnetoresistive effect element provided in the second magnetic detection unit Is directed in a direction along the feedback magnetic field, and the other is directed in a direction opposite to the feedback magnetic field,
Two series units are provided in which the magnetoresistive effect element provided in the first magnetic detection unit and the magnetoresistive effect element provided in the second magnetic detection unit are connected in series. A bridge circuit is formed by the series part of the circuit, and the feedback current is determined according to the output from the bridge circuit.

  The magnetic field detection apparatus of the present invention can be configured as the first coil and the second coil connected in series. Alternatively, the first coil and the second coil can be connected in parallel.

  Furthermore, the magnetic field detection apparatus of the present invention can be provided with a switching unit that switches the connection between the first coil and the second coil between series and parallel.

  The magnetic field detection device of the present invention can be configured such that a current path intersecting the direction of the fixed magnetization of the magnetoresistive effect element is provided, and the measurement magnetic field is induced by a current to be measured flowing in the current path. That is, it can be configured as a current detection device (current sensor).

In the magnetic field detection device of the present invention, the first detection unit and the second detection unit are arranged on the same side with respect to the current path,
The direction of fixed magnetization of the magnetoresistive effect element provided in the first detection unit is opposite to the direction of fixed magnetization of the magnetoresistive effect element provided in the second detection unit.

Alternatively, in the magnetic field detection device of the present invention, the first detection unit and the second detection unit are arranged at a position sandwiching the current path,
The direction of fixed magnetization of the magnetoresistive effect element provided in the first detection unit is the same as the direction of fixed magnetization of the magnetoresistive effect element provided in the second detection unit.

In the magnetoresistive effect element in the magnetic field detection device of the present invention, it is preferable that the magnetization direction of the pinned magnetic layer is set by antiferromagnetic coupling between the pinned magnetic layer and the antiferromagnetic layer.

  Further, in the magnetoresistive effect element in the magnetic field detection device of the present invention, the magnetization of the free magnetic layer is set in a direction orthogonal to the direction of the fixed magnetization by antiferromagnetic coupling with an Ir-Mn alloy. Those are preferred.

  The magnetic field detection apparatus of the present invention is provided with a first detection unit and a second detection unit, each having a coil. In each detection unit, the magnetization directions of the pinned magnetic layers of at least two magnetoresistive elements facing the same coil are aligned in the same direction. Therefore, a plurality of magnetoresistive elements can be easily formed on a common substrate in the same detection unit.

  In the present invention, the magnetization direction of the pinned magnetic layer of the magnetoresistive effect element can be pinned by antiferromagnetic coupling with the antiferromagnetic layer. Problems such as overlapping do not occur.

  Further, by connecting the coil of the first detection unit and the coil of the second detection unit in series or in parallel, it is possible to improve detection sensitivity, widen the dynamic range, and the like.

It is a top view which shows the magnetic field detection apparatus of the 1st Embodiment of this invention, and shows the state by which the coil of the 1st detection unit and the coil of the 2nd detection unit were connected in series, It is a top view which shows the magnetic field detection apparatus of the 1st Embodiment of this invention, and shows the state by which the coil of the 1st detection unit and the coil of the 2nd detection unit were connected in parallel, It is a top view which shows the magnetic field detection apparatus of the 2nd Embodiment of this invention, and shows the state by which the coil of the 1st detection unit and the coil of the 2nd detection unit were connected in series, It is a top view which shows the magnetic field detection apparatus of the 1st Embodiment of this invention, and shows the state by which the coil of the 1st detection unit and the coil of the 2nd detection unit were connected in parallel, The expanded sectional view which cut | disconnected the 1st detection unit with the cut surface extended in Y1-Y2 direction, (A) is explanatory drawing which shows the opposing relationship of the magnetic field detection apparatus of 1st Embodiment, and an electric current path, (B) is description which shows the opposing relation of the magnetic field detection apparatus of 2nd Embodiment, and an electric current path. Figure, (A) is a circuit diagram in which the coil of the first detection unit and the coil of the second detection unit are connected in series, and (B) is the coil of the first detection unit and the coil of the second detection unit. A circuit diagram in which and are connected in parallel, Cross-sectional explanatory drawing showing the film forming process of the magnetoresistive effect element, Cross-sectional explanatory view showing another film forming process of the magnetoresistive effect element, (A) (B) is a diagram for comparing the detection output of the magnetic field detection device in the comparative example and the embodiment, A diagram explaining the connection form of two coils and the effect thereof,

1 and 2 show a plan view of a magnetic field detection apparatus 10 according to a first embodiment of the present invention.
The magnetic field detection device 10 is used as a current sensor IS1, for example, as shown in FIG. In the current sensor IS1, a current path 30 extending in the X direction is provided, and the current to be measured I0 flows in the X direction in the current path 30. The measured current I0 is an alternating current or a direct current.

  The magnetic field detection device 10 includes a first detection unit 1A and a second detection unit 1B. Both the first detection unit 1A and the second detection unit 1B are opposed to the current path 30 on the same side. In the arrangement example shown in FIG. 6A, the first detection unit 1A and the second detection unit 1B are opposed to the lower side (Z1 side) of the current path 30, and the first detection unit 1A is on the Y2 side. The second detection unit 1B is located on the Y1 side.

  As shown in FIG. 1, the first detection unit 1A has a substrate 2A, and the second detection unit 1B has a substrate 2B.

  FIG. 5 shows an enlarged cross-sectional view in which a portion where the first magnetic detection unit 3A of the first detection unit 1A is provided is cut by a cut surface extending in the Y1-Y2 direction.

  As shown in FIG. 5, the first magnetic detector 3 </ b> A is provided on the surface of the substrate 2 </ b> A facing the Z <b> 2 side, and the first magnetic detector 3 </ b> A is covered with the lower insulating layer 4. A conductor layer 5 constituting the first coil (feedback coil) C1 is formed on the lower insulating layer 4. As shown in FIGS. 1 and 2, the conductor layer 5 of the first coil C1 is formed in a spiral locus in a plane pattern parallel to the XY plane along the surface of the substrate 2A. The conductor layer 5 is formed by plating a low resistance metal material such as gold or copper.

  As shown in FIG. 5, the conductor layer 5 constituting the first coil C <b> 1 is covered with the upper insulating layer 6, and the shield layer 7 is formed on the upper insulating layer 6. The shield layer 7 is a plating layer formed of a soft magnetic metal material such as a Ni—Fe alloy (nickel-iron alloy). By providing the plating layer 7, the measurement magnetic field induced by the current I0 to be measured is attenuated and applied to the first magnetic detection unit 3A, and as a result, the dynamic range of the measurement value can be expanded. .

  The laminated structure of the second detection unit 1B is the same as that of the first detection unit 1A, and the second magnetic detection unit 3B is formed on the surface of the substrate 2B. Also in the second detection unit 1B, the second magnetic detection unit 3B is covered with the lower insulating layer 4, and the conductor layer 5 constituting the second coil (feedback coil) C2 is formed on the lower insulating layer 4 in a plane pattern. It is formed in a spiral locus. An upper insulating layer 6 that covers the second coil C <b> 2 is formed, and a shield layer 7 is formed on the upper insulating layer 6.

  As shown in FIGS. 1 and 2, two magnetoresistive elements R <b> 2 and R <b> 3 are provided in the first magnetic detection unit 3 </ b> A provided in the first detection unit 1 </ b> A. The magnetoresistive effect element R2 and the magnetoresistive effect element R3 are arranged at an interval in the X direction, which is the direction in which the measured current I0 flows. Two magnetoresistive elements R1 and R4 are provided in the second magnetic detection unit 3B provided in the second detection unit 1B. The magnetoresistive effect element R1 and the magnetoresistive effect element R4 are arranged at an interval in the X direction, which is the direction in which the measured current I0 flows.

  Each magnetoresistive effect element R1, R2, R3, R4 is composed of a plurality of stripe-shaped GMR elements having a longitudinal dimension in the X direction larger than a width dimension in the Y direction. A plurality of stripe-shaped GMR elements are arranged in a so-called meander pattern and connected in series.

  As shown in FIGS. 1 and 5, the straight portion Ca extending in the X direction of the first coil C1 provided in the first detection unit 1A is located immediately above the magnetoresistive elements R2 and R3. The longitudinal direction of the stripe-shaped GMR element and the conductor layer 5 at the straight line portion Ca are parallel to each other in the X direction. Similarly, the straight line portion Cb extending in the X direction of the second coil C2 provided in the second detection unit 1B is located immediately above the magnetoresistive elements R1 and R4, and has a stripe-shaped GMR. The longitudinal direction of the element and the conductor layer 5 at the straight line portion Cb are opposed in parallel in the X direction.

  The GMR elements that constitute the magnetoresistive elements R1, R2, R3, and R4 are giant magnetoresistive elements that exhibit a giant magnetoresistive effect. The laminated structure of the GMR element will be described in detail later with reference to FIGS. 8 and 9, and the GMR element has a pinned magnetic layer, a nonmagnetic layer, and a free magnetic layer laminated in order.

  The magnetization of the pinned magnetic layer is pinned in the Y direction. That is, the fixed magnetization of the fixed magnetic layer is in a direction orthogonal to the direction of the measured current I0. In the magnetoresistive effect elements R2 and R3 constituting the first magnetic detection unit 3A provided in the first detection unit 1A, the fixed direction Pa of the magnetization of the fixed magnetic layer is the Y2 direction. In the magnetoresistive effect elements R2 and R3, the free magnetic layer is controlled to be close to a single magnetic domain, and the magnetization direction Fa is aligned in the X2 direction by a bias magnetic field of antiferromagnetic coupling described later.

  In the magnetoresistive effect elements R1 and R4 constituting the second magnetic detection unit 3B provided in the second detection unit 1B, the fixed direction Pb of the magnetization of the fixed magnetic layer is the Y1 direction. In the magnetoresistive elements R1 and R4, the free magnetic layer is controlled to a state close to a single magnetic domain, and the magnetization direction Fb is aligned in the X1 direction by a bias magnetic field of antiferromagnetic coupling described later.

  In the magnetoresistive effect elements R1, R2, R3, and R4, the fixed directions Pa and Pb of the magnetization of the fixed magnetic layer are the sensitivity axis directions.

  When a magnetoresistive element R1, R2, R3, R4 is given a measurement magnetic field oriented along the direction of the sensitivity axis (Pa or Pb), the magnetization Fa or Fb that is single-domained in the X direction in the free magnetic layer Is tilted in the Y direction. When the angle between the magnetization vector (Fa or Fb) of the free magnetic layer and the fixed direction Pa or Pb of the magnetization of the pinned magnetic layer decreases, the electrical resistance value of the magnetoresistive effect element decreases. The electrical resistance value of the resistive element increases.

  As shown in FIGS. 1 and 2, in the first detection unit 1A, the power supply pad 11A, the ground pad 12A, the output pad 13A, and the relay pad 14A are formed on the surface of the substrate 2A. Each of these pads 11A, 12A, 13A, 14A and the magnetoresistive effect elements R2, R3 are connected by a plurality of wiring layers 15A indicated by broken lines. Each pad 11A, 12A, 13A, 14A and a plurality of wiring layers 15A are formed of a copper foil layer, a silver paste, or the like on the surface of the substrate 2A.

  Similarly, in the second detection unit 1B, the power supply pad 11B, the ground pad 12B, the output pad 13B, and the relay pad 14B are formed on the surface of the substrate 2B. These pads 11B, 12B, 13B, and 14B and the magnetoresistive elements R1 and R4 are connected by a plurality of wiring layers 15B indicated by broken lines.

  As shown in FIG. 1 and FIG. 2, the first detection unit 1A and the second detection unit 1B have the same basic structure and basic shape composed of the elements described above, and the second detection unit 1B The first detection unit 1A is rotated 180 degrees in the Y direction. Therefore, the magnetic field detection apparatus 10 which combined the 1st detection unit 1A and the 2nd detection unit 1B can be comprised by changing and arrange | positioning the direction of the detection unit of the same structure.

  As shown in FIGS. 1 and 2, each pad 11A, 12A, 13A, 14A of the first detection unit 1A and each pad 11B, 12B, 13B, 14B of the second detection unit 1B are connected by an external wiring 16. It is connected.

  As shown in the circuit diagrams of FIGS. 7A and 7B, the power supply voltage Vdd is applied to the power supply pads 11A and 11B. The magnetoresistive effect element R1 provided in the second detection unit 1B and the magnetoresistive effect element R2 provided in the first detection unit 1A are connected in series. In this series part, the magnetoresistive effect element R1 and An output pad (Out1) 13B is provided at the midpoint of the magnetoresistive element R2. The magnetoresistive effect element R3 provided in the first detection unit 1A and the magnetoresistive effect element R4 provided in the second detection unit 1B are connected in series. In this series part, the magnetoresistive effect element R3 and An output pad (Out2) 13A is provided at the midpoint of the magnetoresistive element R4.

  A series circuit of the magnetoresistive effect elements R1 and R2 and a series part of the magnetoresistive effect elements R3 and R4 are connected in parallel to form a bridge circuit, and a power supply voltage Vdd is applied to the bridge circuit. The two series parts are set to the ground potential by the ground pads 12A and 12B.

  As shown in FIGS. 7A and 7B, the detection output from the output pad (Out 1) 13 B and the detection output from the output pad (Out 2) 13 A are given to the coil energization unit 17 by the external wiring 16. . The coil energization unit 17 includes a differential amplification unit 18 and a compensation circuit 19. The differential amplifier 18 is mainly composed of an operational amplifier, and a difference (Out1-Out2) between two input detection outputs is obtained as a detection voltage Vd. This detection voltage Vd is applied to the compensation circuit 19 to generate a feedback current Id, and the feedback current Id is provided to the first coil C1 and the second detection unit 1B provided in the first detection unit 1A. It is given to the second coil C2.

  A unit in which the differential amplifier 18 and the compensation circuit 19 are integrated may be called a compensation type differential amplifier.

  As shown in FIGS. 1 and 2, the first switching unit SW1 and the second coil C2 are connected between the coil energization unit 17 connected via the external wiring 16, the first coil C1, and the second coil C2. A switching unit SW2 is provided.

  When the switching units SW1 and SW2 are switched to the state shown in FIG. 1, as shown in FIG. 7A, the first coil C1 and the second coil C2 are connected in series, and the detection resistor R is connected in series. Connected to ground. When the switching units SW1 and SW2 are switched to the state shown in FIG. 2, as shown in FIG. 7B, the first coil C1 and the second coil C2 are connected in parallel, and the detection resistor R is connected in series. Connected to ground.

  The switching units SW1 and SW2 are configured by switching elements such as transistors, and in accordance with a switching signal from a control unit (not shown), the series configuration shown in FIGS. 1 and 7A and the parallel configuration shown in FIGS. 2 and 7B are provided. It is switched to. Alternatively, the switching units SW1 and SW2 may be configured with a manual switch mechanism. Alternatively, the switching units SW1 and SW2 fix the wiring by soldering or the like so as to be in the state of FIG. 1 or the state of FIG. 2, so that the series configuration of FIG. The parallel configuration shown in B) may be selected and fixed.

  As shown in FIGS. 7A and 7B, the magnetic field detection device 10 is provided with a current detection unit (voltage detection unit) 21 including a detection resistor R.

Next, the operation of the magnetic field detection device 10 will be described.
As shown in FIG. 6A, both the first detection unit 1A and the second detection unit 1B are arranged side by side below the current path 30 (Z1 side). When the measured current I0 flows in the current path 30 in the X direction, a measurement current magnetic field H0 is induced around the current path 30. As shown in FIGS. 1 and 2, the measurement magnetic field Ha acts on the first detection unit 1A and the measurement magnetic field Hb acts on the second detection unit 1B by the current magnetic field H0. The directions of the measurement magnetic field Ha and the measurement magnetic field Hb are the same regardless of whether they are an alternating magnetic field or a direct magnetic field.

  The magnetoresistive effect elements R2 and R3 facing below the straight line portion Ca of the first coil C1 and the magnetoresistive effect elements R1 and R4 facing below the straight line portion Cb of the second coil C2 are: The directions Pa and Pb of the fixed magnetic layer of the fixed magnetic layer are 180 degrees different from each other, and the directions of magnetization Fa and Fb that are single-domained by the free magnetic layer are 180 degrees different from each other.

  For example, when the magnetization direction Fa of the free magnetic layer of the magnetoresistive effect elements R2 and R3 is tilted in the Y2 direction by the measurement magnetic field Ha and the resistance values of the magnetoresistive effect elements R2 and R3 decrease, the measurement magnetic field Hb Since the direction Fb of the free magnetic layer of the magnetoresistive elements R1 and R4 is tilted in the same Y2 direction, the resistance values of the magnetoresistive elements R1 and R4 are increased. When the directions of the measurement magnetic fields Ha and Hb change, the change in resistance value is opposite to the above. In any case, the resistance values of the magnetoresistive elements R2 and R3 and the magnetoresistive elements R1 and R4 change so as to have opposite polarities.

  Therefore, in the bridge circuit shown in FIGS. 7A and 7B, the potentials of the output pad (Out1) 13B and the output pad (Out2) 13A change according to the magnitude and direction of the measurement magnetic fields Ha and Hb, When the potential increases, the other potential decreases, and the detection voltage Vd, which is the output value of the differential amplifier 15a, changes accordingly. The detection voltage Vd increases as the measured current I0 increases and the induced current magnetic field H0 increases.

  A feedback current (cancellation current) Id is applied from the compensation circuit 19 to the first coil C1 and the second coil C2 according to the increase or decrease of the detection voltage Vd.

  The first coil C1 and the second coil C2 are connected in series as shown in FIG. 1 and when the first coil C1 and the second coil C2 are connected in parallel as shown in FIG. The feedback current Id flows in the same direction through the straight line portion Ca and the straight line portion Cb of the second coil C2. Accordingly, the feedback magnetic field Hd that is induced by the feedback current Id that flows through the straight line portion Ca and acts on the first magnetic detection unit 3A, and the feedback magnetic field Id that is induced by the feedback current Id that flows through the straight line portion Cb acts on the second magnetic detection unit 3B. The feedback magnetic field He is in the same direction.

  For the first magnetic detection unit 3A and the second magnetic detection unit 3B, the feedback magnetic fields Hd and He act in a direction to cancel the measurement magnetic fields Ha and Hb by the current magnetic field H0. When the measurement magnetic fields Ha and Hb induced by the current to be measured I0 are larger than the feedback magnetic fields Hd and He, the absolute value of the detection voltage Vd is increased, and the feedback current Id is increased by the compensation circuit 19 for feedback. The magnetic fields Hd and He increase so that the measurement magnetic fields Ha and Hb are canceled. When the measurement magnetic fields Ha, Hb, the feedback magnetic field Hd, and He acting on the first magnetic detection unit 3A and the second magnetic detection unit 3B are in an equilibrium state, the first coil C1 and the second coil The current value of the feedback current Id flowing through C2 is detected by the current detector 21 shown in FIGS. 7A and 7B, and this becomes the current measurement value of the measured current I0.

  FIG. 11 shows the relationship between the current magnetic field H0 induced by the measured current I0 and the feedback current Id detected by the current detector 21. As shown in FIGS. 1 and 7A, the relationship between the current magnetic field H0 and the feedback current Id when the first coil C1 and the second coil C2 are connected in series is indicated by a straight line α. As shown in FIGS. 2 and 7B, the relationship between the current magnetic field H0 and the feedback current Id when the first coil C1 and the second coil C2 are connected in parallel is shown by a straight line β.

  As shown in FIGS. 2 and 7B, when the first coil C1 and the second coil C2 are connected in parallel, the feedback current Id required to cancel the measurement magnetic fields Ha and Hb is Twice as much as when connected in series. This means that the change width of the feedback current Id detected by the current detector 21 when the current magnetic field H0 changes with a predetermined width is doubled when the current magnetic field H0 is parallel compared to when the current magnetic field H0 is serial. Yes. Therefore, by connecting the first coil C1 and the second coil C2 in parallel, the detection sensitivity for detecting the current magnetic field H0 induced by the measured current I0 is increased.

  On the other hand, the change width of the current magnetic field H0 when the feedback current Id changes with a predetermined width is wider when the coils are in series than when they are parallel. Therefore, by connecting the first coil C1 and the second coil C2 in series, the detection width of the current I0 to be measured can be widened and the dynamic range of measurement can be expanded.

  3 and 4 show a magnetic field detector 20 according to a second embodiment of the present invention. As shown in FIG. 6B, the magnetic field detection device 20 is used as a current sensor IS2. In the current sensor IS2, the first detection unit 1A is opposed to the lower side (Z1 side) than the current path 30, and the second detection unit 1B is opposed to the upper side (Z2 side) than the current path 30. .

  The first detection unit 1A in the magnetic field detection device 20 of the second embodiment shown in FIGS. 3 and 4 has the same structure as the first detection unit 1A shown in FIGS. The second detection unit 1B shown in FIGS. 3 and 4 is the same as the second detection unit 1B shown in FIGS. However, the second detection unit 1B shown in FIGS. 3 and 4 is obtained by rotating the first detection unit shown in FIGS. 1 and 2 180 degrees in the Y1-Y2 direction. That is, in the second embodiment shown in FIGS. 3 and 4, the first detection unit 1A and the second detection unit 1B are used in the same direction with the same structure.

  Therefore, in the magnetic field detection device 20, the fixed direction Pa of the magnetization of the fixed magnetic layer and the magnetization direction Fa of the free magnetic layer in the magnetoresistive effect elements R2 and R3 provided in the first detection unit 1A, and the second The fixed direction Pb of the magnetization of the fixed magnetic layer and the magnetization direction Fb of the free magnetic layer in the magnetoresistive effect elements R1 and R4 provided in the first detection unit 1B are the same.

  However, as shown in FIG. 6B, the measurement magnetic field Ha acting on the first detection unit 1A and the measurement magnetic field Hc acting on the second detection unit 1B by the current magnetic field H0 induced by the measured current I0. Is the opposite.

  As shown in FIGS. 3 and 4, the first detection unit 1 </ b> A and the second detection unit 1 </ b> B are connected to the coil energization unit 17 by an external wiring 26. The external wiring 26 is provided with a third switching unit SW3 and a fourth switching unit SW4. In FIG. 3, the first coil C1 and the second coil C2 are connected in series by the switching operation of the switching units SW3 and SW4. The circuit diagram at this time is the same as FIG. In FIG. 4, the first coil C1 and the second coil C2 are connected in parallel by the switching operation of the switching units SW3 and SW4. The circuit diagram at this time is the same as FIG.

  In both the series connection of FIG. 3 and the parallel connection of FIG. 4, the feedback currents Id flow in opposite directions in the X direction at the straight line portion Ca of the first coil C1 and the straight line portion Cb of the second coil C2. When the feedback current I0 flows in the X1 direction on one side of the linear portions Ca and Cb, it flows in the X2 direction on the other side.

  A bridge circuit including the magnetoresistive effect elements R2 and R3 provided in the first detection unit 1A and the magnetoresistive effect elements R1 and R4 provided in the second detection unit 1B is shown in FIG. Same as B). Therefore, in the magnetic field detection device 20 of the second embodiment, the same detection output as that of the magnetic field detection device 10 of the first embodiment can be obtained for the current I0 to be measured.

  That is, in both the first embodiment and the second embodiment, the two magnetoresistive elements R2 and R3 provided in the first magnetic detection unit 3A have the fixed magnetization Pa of the fixed magnetic layer. The directions are the same, and the two magnetoresistive elements R1 and R4 provided in the second magnetic detection unit 3B have the same direction of the fixed magnetization Pb of the fixed magnetic layer. Further, the direction of the fixed magnetization Pa of the magnetoresistive effect elements R2 and R3 provided in the first magnetic detection unit 3A and the fixed magnetization Pb of the magnetoresistive effect elements R1 and R4 provided in the second magnetic detection unit 3B. One of the directions is directed in a direction along the feedback magnetic field He, and the other is directed in a direction opposite to the feedback magnetic field Hd.

  In the first magnetic detection unit 3A provided in the first detection unit 1A, the magnetization direction Fa of the magnetization of the fixed magnetic layer and the magnetization direction Fa of the free magnetic layer in the two magnetoresistive elements R2 and R3 are Since they are the same, at least two magnetoresistive elements R2 and R3 can be formed together on the same substrate. This also applies to at least two magnetoresistive elements R1 and R4 in the second magnetic detection unit 3B provided in the second detection unit 1B. Here, the at least two magnetoresistive elements are, for example, four magnetoresistive elements in each of the detection units 1A and 1B, and have the same fixed magnetization direction as the fixed magnetic layer and the same magnetization direction as the free magnetic layer. This means that it can be formed in the same direction.

  In each of the detection units 1A and 1B, the fixed magnetization direction of the pinned magnetic layer of the magnetoresistive effect element can be made the same direction. Therefore, the pinned magnetic layer and the antiferromagnetic layer are stacked so that the pinned magnetization of the pinned magnetic layer is depolarized. It can be determined by ferromagnetic coupling. That is, magnetoresistive elements formed on the same substrate in the same sensing unit have the same fixed magnetization direction of the fixed magnetic layer, so that the fixed magnetization directions can be aligned together by annealing in a magnetic field. become.

8 and 9 show a method for manufacturing a GMR element using antiferromagnetic coupling.
In FIG. 8A, an Ir—Mn antiferromagnetic layer 42 is formed on a Ni—Fe—Cr seed layer 41, and a Co—Fe first ferromagnetic layer 43 and Ru are formed thereon. A pinned magnetic layer having a three-layer structure of the intermediate layer 44 and the second ferromagnetic layer 45 of Co—Fe is formed. A Cu nonmagnetic intermediate layer 46 is formed on the second ferromagnetic layer 45 constituting the pinned magnetic layer, and a free magnetic layer 47 having a two-layer structure of a Co—Fe layer and a Ni—Fe layer is formed thereon. Then, an antioxidation layer 48 of Ru is formed.

  In FIG. 8B, annealing in a magnetic field is performed. As a result of this annealing treatment, the magnetization of the first ferromagnetic layer 43 is determined by antiferromagnetic coupling between the antiferromagnetic layer 42 and the first ferromagnetic layer 43. By appropriately setting the thickness of the Ru intermediate layer 44, the magnetization of the second ferromagnetic layer 45 can be fixed in the direction opposite to that of the first ferromagnetic layer 43. In this way, the fixed magnetization (Pin) of the fixed magnetic layer is determined.

  In FIG. 8C, the oxidation preventing layer 48 is completely removed by etching, and the free magnetic layer 47 is partially removed above the Ni—Fe layer. Then, as shown in FIG. 8D, a Co—Fe ferromagnetic layer 49 and an Ir—Mn antiferromagnetic layer 51, which are part of the free magnetic layer, are continuously formed in a magnetic field. Further, a Ta cap layer 52 is formed. By forming the Ir—Mn antiferromagnetic layer 51 in a magnetic field, a bias magnetic field can be applied to the free magnetic layer in which the layer 47 and the layer 49 are overlapped without undergoing an annealing process. The layer can be made into a single magnetic domain, and the direction of magnetization thereof can be aligned with the direction perpendicular to the direction of fixed magnetization of the fixed magnetic layer.

  Next, in the manufacturing method shown in FIG. 9, the seed layer 41, the antiferromagnetic layer 42, the first ferromagnetic layer 43, the intermediate layer 44, the second ferromagnetic layer 45, and the nonmagnetic intermediate layer 46 in FIG. Then, the free magnetic layer 47 is formed, and then the Pt layer is formed as the antioxidant layer 53 instead of the Ru layer. In FIG. 9B, annealing in a magnetic field is performed, the magnetization of the first ferromagnetic layer 43 and the second ferromagnetic layer 45 is fixed by antiferromagnetic coupling, and the fixed magnetization (Pin) of the fixed magnetic layer is It is decided.

  In FIG. 9D, the Ni—Fe layer 54, the ferromagnetic layer 49, and the Ir—Mn antiferromagnetic layer 51 are formed in a magnetic field on the Pt layer without removing the antioxidant layer 53. . Since the Pt layer performs ferromagnetic coupling, the magnetization of the free magnetic layer composed of the layers 47, 54, and 49 is determined in a direction orthogonal to the fixed magnetization (Pin) of the fixed magnetic layer.

  FIG. 10A shows, as a comparative example, a magnetic field detection device using a GMR element using a self-locking ferromagnetic pinned layer shown in Patent Documents 1 and 2, and FIG. FIG. 9 shows an embodiment in which the magnetization direction of the pinned magnetic layer is fixed by antiferromagnetic coupling by annealing in a magnetic field.

  10A and 10B, the horizontal axis represents the intensity of the measured magnetic field, and the vertical axis represents the detection output (voltage output) of the current sensor. In the comparative example and the example, the solid line indicates the initial operating characteristics, and the broken line indicates the operating characteristics after exposure to a strong magnetic field of 500 mT. In the comparative example shown in FIG. 10A, when exposed to a strong magnetic field, the pinned magnetization of the pinned magnetic layer becomes unstable, and a bias value is superimposed on the output. On the other hand, in the embodiment shown in FIG. 10B, the magnetization of the fixed magnetic layer is stably fixed, and an output in which noise due to bias is not superimposed can be obtained.

DESCRIPTION OF SYMBOLS 1A 1st detection unit 1B 2nd detection unit 2A, 2B Board | substrate 3A 1st magnetic detection part 3B 2nd magnetic detection part 10 Magnetic field detection apparatus 17 Coil current supply part 20 Magnetic field detection apparatus 21 Current detection part 30 Current path 42 Antiferromagnetic layer 43 First ferromagnetic layer 44 Intermediate layer 45 Second ferromagnetic layer 46 Nonmagnetic intermediate layer 47 Free magnetic layer 51 Antiferromagnetic layer C1 First coil C2 Second coils Ca, Cb Linear portion Fa, Fb Magnetization direction of free magnetic layer H0 Current magnetic field Ha, Hb Measurement magnetic field Hd, He Feedback magnetic field I0 Current to be measured IS1, IS2 Current sensor Id Feedback current Pa, Pb Fixed direction of magnetization R1, R2, fixed magnetic layer R3, R4 magnetoresistive effect element R detection resistance SW1, SW2, SW3, SW4 switching part Vd detection voltage

Claims (9)

A magnetic detection unit whose detection output changes according to the strength of the measurement magnetic field, a coil that gives the magnetic detection unit a feedback magnetic field opposite to the measurement magnetic field, and a coil that responds to the detection output of the magnetic detection unit In a magnetic field detection device provided with a coil energization unit for supplying a feedback current for inducing the feedback magnetic field and a detection unit for detecting the amount of current flowing in the coil,
A first detection unit and a second detection unit are provided, and the first detection unit includes a first magnetic detection unit and a first coil that applies the feedback magnetic field to the first magnetic detection unit. Provided, the second detection unit is provided with a second magnetic detection unit, and a second coil that applies the feedback magnetic field to the second magnetic detection unit,
The first magnetic detection unit and the second magnetic detection unit each include at least two magnetoresistive effect elements whose resistance values change according to the magnetization directions of the free magnetic layer and the pinned magnetic layer,
The at least two magnetoresistive elements provided in the first magnetic detection unit have the same fixed magnetization direction of the fixed magnetic layer, and at least two magnetoresistive elements provided in the second magnetic detection unit. The magnetoresistive element has the same fixed magnetization direction of the fixed magnetic layer,
One of the fixed magnetization direction of the magnetoresistive effect element provided in the first magnetic detection unit and the fixed magnetization direction of the magnetoresistive effect element provided in the second magnetic detection unit Is directed in a direction along the feedback magnetic field, and the other is directed in a direction opposite to the feedback magnetic field,
Two series units are provided in which the magnetoresistive effect element provided in the first magnetic detection unit and the magnetoresistive effect element provided in the second magnetic detection unit are connected in series. A magnetic field detector according to claim 1, wherein a bridge circuit is formed by the serial portion of the first and second feedback circuits, and the feedback current is determined in accordance with an output from the bridge circuit.   The magnetic field detection apparatus according to claim 1, wherein the first coil and the second coil are connected in series.   The magnetic field detection apparatus according to claim 1, wherein the first coil and the second coil are connected in parallel.   The magnetic field detection apparatus according to claim 1, further comprising a switching unit that switches a connection between the first coil and the second coil between series and parallel.   5. The magnetic field detection device according to claim 1, wherein a current path intersecting with the direction of the fixed magnetization of the magnetoresistive effect element is provided, and the measurement magnetic field is induced by a measured current flowing in the current path. . The first detection unit and the second detection unit are disposed on the same side with respect to the current path;
The direction of fixed magnetization of the magnetoresistive effect element provided in the first detection unit is opposite to the direction of fixed magnetization of the magnetoresistive effect element provided in the second detection unit. Item 6. The magnetic field detection device according to Item 5. The first detection unit and the second detection unit are arranged at positions sandwiching the current path,
The fixed magnetization direction of the magnetoresistive effect element provided in the first detection unit and the fixed magnetization direction of the magnetoresistive effect element provided in the second detection unit are in the same direction. Item 6. The magnetic field detection device according to Item 5. 8. The magnetic field detection according to claim 1, wherein the magnetoresistive element has a magnetization direction of the pinned magnetic layer set by antiferromagnetic coupling between the pinned magnetic layer and an antiferromagnetic layer. 9. apparatus.   The magnetic field detection device according to claim 8, wherein the magnetoresistive element is set so that the magnetization of the free magnetic layer is orthogonal to the direction of the fixed magnetization by antiferromagnetic coupling with an Ir—Mn alloy.