JP5006339B2 - Magnetic detector - Google Patents

Description

  The present invention relates to a magnetic detection device including a magnetoresistive effect element, and more particularly to a magnetic detection device capable of bipolar detection.

  Recently, a magnetic detection device including a magnetic detection element has been adopted for opening / closing detection of a folding cellular phone.

  As the magnetic detection element, a Hall element or a magnetoresistive effect element is used. Unlike the Hall element, the magnetoresistive element appropriately changes its electric resistance even with a weak external magnetic field, and can be expected to have a long life.

  As the magnetoresistive effect element, a GMR element using a giant magnetoresistive effect (GMR effect) is employed.

The RH curve (hysteresis loop) 1 of the GMR element is shifted to the external magnetic field side in the (+) direction, for example, as shown in FIG. That is, when the external magnetic field H in the (+) direction enters the GMR element, the electric resistance value R changes along the RH curve 1 shown in FIG.
JP 2005-214900 A JP 2004-180286 A

  However, in the GMR element having the RH curve 1 shown in FIG. 8, the electric resistance does not change with respect to the intensity change of the external magnetic field H in the (−) direction which is the opposite direction to the (+) direction.

  Therefore, when the external magnetic field H in the (−) direction enters, the electrical resistance of the GMR element does not change, so that the external magnetic field in the (−) direction cannot be detected.

  Therefore, when a folding mobile phone is equipped with a GMR element having the RH curve 1 shown in FIG. 8, the magnet is so that an external magnetic field H in the (+) direction acts on the GMR element from the magnet when the folding mobile phone is opened and closed. Had to be placed properly.

  Further, by using a GMR element whose RH curve is shifted to the external magnetic field side in the (−) direction together with the GMR element having the RH curve 1 shown in FIG. 8, the (+) direction and (−) direction An external magnetic field in either direction can be detected.

  However, in such a case, there is a problem that the number of elements increases. In particular, since the GMR element for detecting the external magnetic field in the (+) direction and the GGMR element for detecting the external magnetic field in the (−) direction are not the same configuration, such as being formed with different film thicknesses, they are manufactured by separate manufacturing processes. It was necessary to do. Therefore, there is a problem that the manufacturing process becomes complicated.

  In the inventions described in Patent Documents 1 and 2 described above, it is described that the magnetic detection element incorporated in the magnetic detection device is a magnetoresistive effect element utilizing the magnetoresistive effect. In particular, the invention described in Patent Document 1 discloses a magnetic detection device capable of bipolar detection.

  However, the invention described in Patent Document 1 does not disclose a specific configuration of the magnetoresistive element. That is, the specific configuration of the magnetoresistive effect element having the characteristics shown in FIG. 2 of Patent Document 1 is not disclosed.

  SUMMARY OF THE INVENTION The present invention is intended to solve the above-described conventional problems, and in particular, an object of the present invention is to provide a magnetic detection device capable of performing bipolar detection with a simple element structure.

The magnetic detection device in the present invention is
It has a magnetoresistive effect element using a magnetoresistive effect whose electric resistance changes with respect to an external magnetic field,
The magnetoresistive effect element has a laminated structure of a first laminated body and a second laminated body,
The first laminate has a configuration in which a first pinned magnetic layer and a first free magnetic layer are laminated via a first nonmagnetic material layer, and an electric resistance changes with respect to an external magnetic field in the (+) direction. ,
The second stacked body has a configuration in which a second pinned magnetic layer and a second free magnetic layer are stacked via a second nonmagnetic material layer, and is in a (−) direction opposite to the (+) direction. The electrical resistance changes with respect to the external magnetic field,
When the external magnetic field in the (+) direction enters, the external magnetic field in the (+) direction is detected by changing the electric resistance value of the first laminate, and the external magnetic field in the (−) direction enters. In this case, the external magnetic field in the (−) direction is detected by changing the electric resistance value of the second stacked body.

  In the present invention, the magnetoresistive effect element includes a first stacked body whose electrical resistance changes with respect to an external magnetic field in the (+) direction, and a second stacked body whose electrical resistance changes with respect to an external magnetic field in the (−) direction. It is formed in a laminated structure with the body. Thereby, bipolar detection can be realized with a simple element structure.

The magnetoresistive effect element employed in the present invention is
On the RH graph, the horizontal axis is the magnitude of the external magnetic field H and the vertical axis is the resistance value R of the magnetoresistive element.
A first interlayer coupling magnetic field Hin1 acting between the first pinned magnetic layer and the first free magnetic layer appears on the external magnetic field side in the (+) direction, and between the second pinned magnetic layer and the second free magnetic layer. The acting second interlayer coupling magnetic field Hin2 appears on the external magnetic field side in the (−) direction,
When the electric resistance value of the magnetoresistive effect element when the external magnetic field is zero is used as a reference, the increase / decrease tendency of the electric resistance value of the magnetoresistive effect element with respect to the change in the intensity of the external magnetic field in the (+) direction; The increase / decrease tendency of the electric resistance value of the magnetoresistive effect element with respect to the change in the intensity of the external magnetic field in the direction shows a reverse tendency.

  This enables proper bipolar detection with a simple element configuration. In particular, the increase / decrease tendency of the resistance value with respect to the change in the intensity of the external magnetic field in the (+) direction and the resistance value with respect to the change in the intensity of the external magnetic field in the (−) direction. When the increase / decrease tendency shows a reverse tendency, it is possible to detect even the direction of the detected external magnetic field.

In the present invention, two magnetoresistive effect elements are prepared, one magnetoresistive effect element is connected in series to the first fixed resistance element via the first output extraction section, and the other magnetoresistive effect element is It is connected in series to the second fixed resistance element via the second output extraction unit,
The fixed resistance value R3 of the first fixed resistance element is equal to the electric resistance value R1 of the magnetoresistive effect element when the external magnetic field is zero and the external magnetic field is zero when the external magnetic field in the (+) direction acts. A value between the electric resistance value R2 of the magnetoresistive effect element and the electric resistance value R2 of the magnetoresistive effect element that has changed to the maximum from the electric resistance value R1. The electric resistance value R1 when the magnetic field is zero and the electric resistance of the magnetoresistive effect element changed to the maximum from the electric resistance value R1 when the external magnetic field is zero when an external magnetic field in the (−) direction is applied. It is preferably a value between the resistance value R4.

  In particular, the fixed resistance value R3 of the first fixed resistance element is an intermediate value between the electric resistance value R1 and the electric resistance value R2 of the magnetoresistive effect element, and the fixed resistance value R5 of the second fixed resistance element is: More preferably, the magnetoresistive element has an intermediate value between the electric resistance value R1 and the electric resistance value R4.

  In the present invention, by using one type of magnetoresistive effect element and two types of fixed resistance elements having different fixed resistance values, it is possible to realize a magnetic detection device capable of handling bipolar. That is, it is not necessary to use a plurality of types of magnetoresistive effect elements as in the prior art. Moreover, it is possible to make a circuit configuration capable of detecting even the direction of the acting external magnetic field.

In the present invention, a first series circuit in which a magnetoresistive effect element and a first fixed resistance element are connected in series, a second series circuit in which a magnetoresistive effect element and a second fixed resistance element are connected in series, and a fixed resistance A third series circuit in which the elements are connected in series via a third output extraction unit;
One of the first output extraction unit of the first series circuit and the second output extraction unit of the second series circuit are respectively connected to a common differential output unit via a connection switching unit. Connected together with
In the connection switching unit, when the first output extraction unit and the differential output unit are connected, the first bridge circuit formed by connecting the first series circuit and the third series circuit in parallel is the difference. When the second output extraction unit and the differential output unit are connected in the connection switching unit, the second series circuit and the third series circuit are switched to the state connected to the dynamic output unit. It is preferable that the second bridge circuit connected in parallel is switched to the state connected to the differential output unit.

  The first bridge circuit is a side that detects an external magnetic field in the (+) direction, and the second bridge circuit is a side that detects an external magnetic field in the (−) direction. In the present invention, the two bridge circuits can be obtained with a small number of elements and a simple circuit configuration.

  In the present invention, the magnetoresistive effect element includes a first stacked body whose electrical resistance changes with respect to an external magnetic field in the (+) direction, and a second stacked body whose electrical resistance changes with respect to the external magnetic field in the (−) direction. And a laminated structure. Thereby, bipolar detection can be realized with a simple element structure.

  FIG. 1 is a circuit configuration diagram of a magnetic detection device 20 of the present embodiment, FIG. 2 is an RH graph for explaining an RH curve of the magnetoresistive effect element, and FIG. 3 shows a layer structure of the magnetoresistive effect element. Partial sectional views and FIGS. 4 to 7 are examples for explaining the use of the magnetic detection device according to the present embodiment, and are schematic views of a foldable mobile phone incorporating the magnetic detection device.

  A magnetic detection device 20 of this embodiment shown in FIG. 1 includes an element configuration unit 21 and an integrated circuit (IC) 22.

  The element configuration unit 21 includes a first series circuit 26 in which a magnetoresistive effect element 23 and a first fixed resistance element 24 are connected in series via a first output extraction unit 25, a magnetoresistive effect element 27, and a second fixed resistance. A second series circuit 30 in which the element 28 is connected in series via the second output extraction section 29, and a third series in which the fixed resistance element 31 and the fixed resistance element 32 are connected in series via the third output extraction section 33. It is composed of a series circuit 34.

  The third series circuit 34 forms a bridge circuit with the first series circuit 26 and the second series circuit 30 as a common circuit. Hereinafter, a bridge circuit formed by connecting the first series circuit 26 and the third series circuit 34 in parallel is referred to as a first bridge circuit BC1, and the second series circuit 30 and the third series circuit 34 are connected in parallel. This bridge circuit is referred to as a second bridge circuit BC2.

  As shown in FIG. 1, in the first bridge circuit BC1, a magnetoresistive effect element 23 and a fixed resistance element 32 are connected in parallel, and the first fixed resistance element 24 and the fixed resistance element 31 are connected in parallel. It is connected. In the second bridge circuit BC2, the magnetoresistive effect element 27 and the fixed resistance element 31 are connected in parallel, and the second fixed resistance element 28 and the fixed resistance element 32 are connected in parallel. .

  As shown in FIG. 1, the integrated circuit 22 is provided with an input terminal (power source) 39, a ground terminal 42, and two external output terminals 40 and 41. The input terminal 39, the ground terminal 42, and the external output terminals 40 and 41 are electrically connected to terminal portions on the device side (not shown) by wire bonding, die bonding or the like.

  A signal line 50 connected to the input terminal 39 and a signal line 51 connected to the ground terminal 42 are provided at both ends of the first series circuit 26, the second series circuit 30, and the third series circuit 34. Connected to each of the electrodes.

  As shown in FIG. 1, one differential amplifier (differential output unit) 35 is provided in the integrated circuit 22. The third output extraction unit 33 of the third series circuit 34 is connected to either the + input unit or the − input unit of the differential amplifier 35. Note that the connection between the third output extraction unit 33 and the differential amplifier 35 is fixed (not disconnected).

  The first output extraction section 25 of the first series circuit 26 and the second output extraction section 29 of the second series circuit 30 are connected to the input section of the first switch circuit (first connection switching section) 36, respectively. The output section of the first switch circuit 36 is connected to either the − input section or the + input section of the differential amplifier 35 (to the input section to which the third output extraction section 33 is not connected). Has been.

  As shown in FIG. 1, the output section of the differential amplifier 35 is connected to a Schmitt trigger type comparator 38, and the output section of the comparator 38 is an input of a second switch circuit (second connection switching section) 43. Connected to the department. Further, the output section of the second switch circuit 43 is connected to the first external output terminal 40 and the second external output terminal 41 via the two latch circuits 46 and 47 and the FET circuits 54 and 55, respectively.

  Further, as shown in FIG. 1, a third switch circuit (third connection switching unit) 48 is provided in the integrated circuit 22. The output part of the third switch circuit 48 is connected to a signal line 51 connected to the ground terminal 42, and the first series circuit 26 and the second series circuit are connected to the input part of the third switch circuit 48. One end of 30 is connected.

  Further, as shown in FIG. 1, an interval switch circuit 52 and a clock circuit 53 are provided in the integrated circuit 22. When the switch of the interval switch circuit 52 is turned off, the power supply to the integrated circuit 22 is stopped. The on / off of the switch of the interval switch circuit 52 is interlocked with the clock signal from the clock circuit 53, and the interval switch circuit 52 has a power saving function for intermittently energizing.

  The clock signal from the clock circuit 53 is also output to each of the first switch circuit 36, the second switch circuit 43, and the third switch circuit 48.

  The magnetoresistive effect element 23 and the magnetoresistive effect element 27 have the same layer structure. The magnetoresistive elements 23 and 27 are formed of a stacked structure of a first stacked body 60 and a second stacked body 61. The laminated structure of the magnetoresistive effect elements 23 and 27 will be described with reference to FIG.

  As shown in FIG. 3, the magnetoresistive elements 23 and 27 are arranged on the installation surface 62 from below, from the seed layer 63, the first antiferromagnetic layer 64, the first pinned magnetic layer 65, and the first nonmagnetic material layer 66. The first free magnetic layer 67, the intermediate separation layer 68, the second free magnetic layer 69, the second nonmagnetic material layer 70, the second pinned magnetic layer 71, the second antiferromagnetic layer 72, and the protective layer 73 are laminated in this order. ing.

  As shown in FIG. 3, the first stacked body 60 includes a first antiferromagnetic layer 64, a first pinned magnetic layer 65, a first nonmagnetic material layer 66, and a first free magnetic layer 67. The second stacked body 61 includes a second free magnetic layer 69, a second nonmagnetic material layer 70, a second pinned magnetic layer 71, and a second antiferromagnetic layer 72. The first stacked body 60 and the second stacked body 61 are magnetically separated by an intermediate separating layer 68.

  As shown in FIG. 3, the first pinned magnetic layer 65 has a laminated ferrimagnetic structure in which a first magnetic layer 65a, a nonmagnetic intermediate layer 65b, and a second magnetic layer 65c are laminated in this order from the bottom. The second pinned magnetic layer 71 has a laminated ferrimagnetic structure in which the second magnetic layer 71c, the nonmagnetic intermediate layer 71b, and the first magnetic layer 71a are laminated in this order from the bottom.

  The magnetization directions of the first magnetic layers 65a and 71a and the second magnetic layers 65c and 71c constituting the laminated ferrimagnetic structure are antiparallel.

  The seed layer 63 is made of NiFeCr or Cr. The first antiferromagnetic layer 64 and the second antiferromagnetic layer 72 include an element α (where α is one or more of Pt, Pd, Ir, Rh, Ru, and Os). Antiferromagnetic material containing Mn, or element α and element α ′ (where element α ′ is Ne, Ar, Kr, Xe, Be, B, C, N, Mg, Al, Si, P, Ti , V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, Cd, Sn, Hf, Ta, W, Re, Au, Pb, and rare earth elements Or two or more elements) and Mn. For example, the first antiferromagnetic layer 64 and the second antiferromagnetic layer 72 are made of IrMn or PtMn. The first magnetic layers 65a and 71a, the second magnetic layers 65c and 71c, the first free magnetic layer 67, and the second free magnetic layer 69 are each formed of a magnetic material such as a CoFe alloy, a NiFe alloy, or a CoFeNi alloy. The first nonmagnetic material layer 66 and the second nonmagnetic material layer 70 are made of Cu, for example. The nonmagnetic intermediate layers 65b and 71b are made of Ru, for example. The intermediate separation layer 68 is made of Cu, for example. The protective layer 73 is made of Ta, for example.

  When the right direction on the paper is the (+) direction and the left direction on the paper is the (−) direction, as shown in FIG. 3, the magnetization directions of the first magnetic layers 65a and 71a are the (+) direction, the second magnetic layer 65c, The magnetization direction of 71c is the (−) direction. The magnetizations of the first magnetic layers 65a and 71a and the second magnetic layers 65c and 71c are fixed so as not to fluctuate due to an external magnetic field.

  FIG. 3 shows a non-magnetic state where no external magnetic field is acting. As shown in FIG. 3, in the non-magnetic field state, the magnetization direction of the first free magnetic layer 67 is the (−) direction, and the magnetization direction of the second free magnetic layer 69 is the (+) direction. The magnetization of the free magnetic layers 67 and 69 varies with an external magnetic field.

  The giant magnetoresistive effect (GMR effect) is expressed by the relationship between the magnetization directions of the second magnetic layers 65c and 71c and the free magnetic layers 67 and 69. That is, when the magnetization directions of the second magnetic layers 65c and 71c and the free magnetic layers 67 and 69 are in a parallel state, the electric resistance value becomes the minimum value, and the second magnetic layers 65c and 71c and the free magnetic layers 67, 69 When the magnetization direction with respect to 69 is in an antiparallel state, the electric resistance value becomes the maximum value.

  Now, when the external magnetic field H acts in the (+) direction, the magnetization of the first free magnetic layer 67 of the first stacked body 60 changes. On the other hand, since the magnetization direction of the second free magnetic layer 69 is the (+) direction, the magnetization does not fluctuate even when the external magnetic field H in the (+) direction acts. Therefore, the electrical resistance value of the second stacked body 61 remains constant.

  As the magnetic field strength of the external magnetic field H in the (+) direction gradually increases, the magnetization direction of the first free magnetic layer 67 gradually changes to the (+) direction. As a result, the magnetization relationship between the first free magnetic layer 67 and the second magnetic layer 65c gradually changes from the parallel state to the anti-parallel state, and the electric resistance value R of the magnetoresistive effect elements 23 and 27 becomes the first RH curve C1 shown in FIG. It grows gradually along the top.

  On the other hand, when the external magnetic field H acts in the (−) direction, the magnetization of the second free magnetic layer 69 of the second stacked body 61 varies. On the other hand, since the magnetization direction of the first free magnetic layer 67 is the (−) direction, the magnetization does not fluctuate even when the external magnetic field H in the (−) direction acts. Therefore, the electrical resistance value of the first stacked body 60 remains constant.

  As the magnetic field strength of the external magnetic field H in the (−) direction gradually increases, the magnetization direction of the second free magnetic layer 69 gradually changes to the (−) direction. As a result, the magnetization relationship between the second free magnetic layer 69 and the second magnetic layer 71c gradually changes from the antiparallel state to the parallel state, and the electric resistance value R of the magnetoresistive effect elements 23 and 27 becomes the second RH curve C2 shown in FIG. It gradually gets smaller along the top.

  As shown in FIG. 2, the first RH curve C1 and the second RH curve C2 are in a loop shape having a predetermined width (meaning that there is hysteresis).

  The magnitude of the first interlayer coupling magnetic field Hin1 is determined by the strength of the magnetic field from the center of the first RH curve C1 formed in a loop shape to the line of the external magnetic field H = 0 (Oe). The first interlayer coupling magnetic field Hin1 acts between the first pinned magnetic layer 65 and the first free magnetic layer 67, and appears on the external magnetic field side in the (+) direction on the RH graph. Yes.

  The magnitude of the second interlayer coupling magnetic field Hin2 is determined by the strength of the magnetic field from the center of the second RH curve C2 formed in a loop shape to the line of the external magnetic field H = 0 (Oe). The second interlayer coupling magnetic field Hin2 acts between the second pinned magnetic layer 71 and the second free magnetic layer 69, and appears on the external magnetic field side in the (−) direction on the RH graph. Yes.

  The interlayer coupling magnetic fields Hin1 and Hin2 described above can be obtained by adjusting the film thickness of the first nonmagnetic material layer 66 and the second nonmagnetic material layer 70, adjusting the interface roughness, or the like.

  The magnetoresistive effect elements 23 and 27 described above are GMR elements using the giant magnetoresistive effect (GMR effect), but may be TMR elements using the tunnel magnetoresistive effect (TMR effect).

  In FIG. 3, the pinned magnetic layers 65 and 71 have a laminated ferrimagnetic structure, but other structures such as a single layer structure or a laminated structure of magnetic layers may be used.

  As shown in FIG. 1, the magnetoresistive effect elements 23 and 27 are connected in series with fixed resistance elements 24 and 28, respectively.

  The fixed resistance value R3 of the first fixed resistance element 24 connected in series to the magnetoresistive effect element 23 is, as shown in FIG. 2, the electrical resistance value R1 of the magnetoresistive effect element 23 when the external magnetic field H is zero. And the maximum electric resistance value R2 of the magnetoresistive element 23 when the external magnetic field H in the (+) direction is applied.

  Further, the fixed resistance value R5 of the second fixed resistance element 28 connected in series to the magnetoresistive effect element 27 has an electric resistance when the external magnetic field H of the magnetoresistive effect element 27 is zero, as shown in FIG. It is adjusted to be an intermediate value between the value R1 and the minimum electric resistance value R4 of the magnetoresistive element 27 when an external magnetic field in the (−) direction is applied.

  For example, the fixed resistance elements 24 and 28 have the same material layer structure as the magnetoresistive effect elements 23 and 27 shown in FIG. 3, but have a structure in which the stacking order is different and the electric resistance does not change with respect to an external magnetic field. The In such a case, it is preferable because variations in the temperature coefficient (TCR) between the fixed resistance elements 24 and 28 and the magnetoresistive effect elements 23 and 27 can be suppressed, and the operational stability can be improved.

  The fixed resistance elements 31 and 32 constituting the third series circuit 34 also have the same material layer structure as that of the magnetoresistive effect elements 23 and 27, for example. Differently, it has a structure in which the electric resistance does not change with respect to the external magnetic field. At this time, the fixed resistance values of the fixed resistance elements 31 and 32 are both adjusted to be the same value.

  The magnetoresistive effect elements 23 and 27 and the fixed resistance elements 24, 28, 31, and 32 are provided on the surface of the magnetic detection device 20 capable of sensing an external magnetic field. The magnetoresistive effect elements 23, 27 and the fixed resistance elements 24, 28, 31, 32 are formed in a meander shape. Thereby, the element resistance of each element can be increased and current consumption can be reduced.

  Instead of FIG. 1, the fixed resistance elements 31 and 32 constituting the third series circuit 34 may be incorporated in the integrated circuit 22. At this time, it is preferable that the fixed resistance elements 31 and 32 are formed of a high resistance material to more appropriately reduce current consumption. For example, the fixed resistance elements 31 and 32 are made of Si.

Next, the principle of detecting an external magnetic field will be described.
As shown in FIG. 1, when the first output extraction unit 25 and the differential amplifier 35 are connected by the first switch circuit 36, the first bridge circuit BC1 is connected to the differential amplifier 35. At this time, the differential amplifier 35 and the first external output terminal 40 are connected by the second switch circuit 43, and the first series circuit 26 and the ground terminal 42 are connected by the third switch circuit 48. Yes.

  The magnitude of the external magnetic field H acting on the magnetic detection device 20 is within the “use range” shown in FIG. Within the “use range”, an external magnetic field strong enough to change the magnetization direction of the pinned magnetic layers 65 and 71 does not act. That is, the magnetizations of the pinned magnetic layers 65 and 71 remain fixed.

  First, in the circuit state of FIG. 1, when an external magnetic field H in the (+) direction acts on the magnetic detection device 20 of the present embodiment, the electrical resistance value R of the magnetoresistive effect element 23 becomes the first value from R1 shown in FIG. It gradually increases along the 1RH curve C1.

  When the electrical resistance value R of the magnetoresistive effect element 23 gradually increases from R1 due to the intensity change of the external magnetic field H in the (+) direction, and eventually exceeds the fixed resistance value R3 of the first fixed resistance element 24, the differential Based on the differential potential generated by the amplifier 35, the comparator 38 generates an ON signal (magnetic field detection signal), and the ON signal is output from the first external output terminal 40.

  The first switch circuit 36, the second switch circuit 43 and the third switch circuit 48 receive the clock signal from the clock circuit 53 and perform a switching operation in conjunction with each other. When the second output extraction unit 29 and the differential amplifier 35 are connected by the first switch circuit 36, the second bridge circuit BC2 is connected to the differential amplifier 35. At this time, the differential amplifier 35 and the second external output terminal 41 are connected by the second switch circuit 43, and the second series circuit 30 and the ground terminal 42 are connected by the third switch circuit 48. .

  In the above circuit state, when the external magnetic field H in the (−) direction acts on the magnetic detection device 20 of the present embodiment, the electric resistance value R of the magnetoresistive effect element 27 changes from R1 shown in FIG. It gradually gets smaller along.

  When the electric resistance value R of the magnetoresistive effect element 27 gradually decreases from R1 due to a change in the intensity of the external magnetic field H in the (−) direction and eventually falls below the resistance value R5 of the second fixed resistance element 28, the differential Based on the differential potential generated by the amplifier 35, the comparator 38 generates an ON signal (magnetic field detection signal), and the ON signal is output from the second output terminal 41.

  As described above, in the magnetic detection device 20 of the present embodiment, the magnetoresistive effect elements 23 and 27 are formed by the stacked structure of the first stacked body 60 and the second stacked body 61 shown in FIG. The first stacked body 60 has a structure using a magnetoresistive effect in which the electric resistance changes with respect to the external magnetic field H in the (+) direction, and the second stacked body 61 has an external magnetic field in the (−) direction. Thus, the structure utilizes the magnetoresistive effect in which the electrical resistance changes.

  Therefore, by using the magnetoresistive effect elements 23 and 27, the external magnetic field H is generated regardless of the external magnetic field H in the (+) direction or the (−) direction on the magnetic detection device 20. It is possible to detect. That is, bipolar detection is possible.

  In the present embodiment, the magnetoresistive effect elements 23 and 27 are constituted by one type of magnetoresistive effect element. That is, as shown in FIG. 1, two magnetoresistive elements 23 and 27 are prepared, but the magnetoresistive elements 23 and 27 have the same layer structure (the thickness of each layer is the same at this time). Therefore, it can be formed by the same manufacturing process, and can be manufactured easily and appropriately.

  As shown in FIG. 2, the first interlayer coupling magnetic field Hin1 acting between the first pinned magnetic layer 65 and the first free magnetic layer 67 constituting the first stacked body 60 is in the (+) direction on the RH graph. It is expressed on the external magnetic field side. Further, as shown in FIG. 2, the second interlayer coupling magnetic field Hin2 acting between the second pinned magnetic layer 71 and the second free magnetic layer 69 constituting the second stacked body 61 is represented by (− ) Direction on the external magnetic field side.

  Then, as shown in FIG. 2, when the electric resistance value R1 of the magnetoresistive effect elements 23 and 27 at the position where the external magnetic field H is zero is used as a reference, the magnetic field strength change of the external magnetic field H in the (+) direction. The increasing / decreasing tendency of the electric resistance values of the magnetoresistive effect elements 23 and 27 and the increasing / decreasing tendency of the electric resistance values of the magnetoresistive effect elements 23 and 27 with respect to the change in the magnetic field intensity of the external magnetic field H in the (−) direction show opposite trends. ing. That is, when the external magnetic field in the (+) direction gradually increases, the electric resistance values of the magnetoresistive elements 23 and 27 show a tendency to increase gradually from R1, while the external magnetic field H in the (−) direction. As the value gradually increases, the electric resistance values of the magnetoresistive elements 23 and 27 tend to decrease gradually from R1.

  And the magnetoresistive effect elements 23 and 27 have the step type RH curve which consists of the 1st RH curve C1 and the 2nd RH curve C2 which are shown in FIG. Thereby, it is possible to realize the magnetic detection device 20 compatible with bipolar detection with a simple circuit configuration, and to detect the action direction of the external magnetic field.

  As shown in FIG. 2, it is possible to detect the action direction of the external magnetic field in the first RH curve C1 in which the electric resistance values of the magnetoresistive effect elements 23 and 27 change with respect to the external magnetic field H in the (+) direction. This is because the resistance change region is different from the resistance change region of the second RH curve C2 in which the electric resistance values of the magnetoresistive effect elements 23 and 27 change with respect to the external magnetic field H in the (−) direction.

  As shown in FIG. 1, two external output terminals 40 and 41 are provided. The first external output terminal 40 is connected to the first bridge circuit BC1. In the first bridge circuit BC1, the external magnetic field H in the (+) direction acts, and the electric resistance value of the magnetoresistive effect element 23 is reduced. When the fixed resistance value R3 of the first fixed resistance element 24 shown in FIG. 2 is exceeded, an ON signal is output from the first external output terminal 40. In other words, an OFF signal is always output from the first external output terminal 40 when the electrical resistance value of the magnetoresistive effect element 23 is lower than the fixed resistance value R3 of the first fixed resistance element 24. On the other hand, the second external output terminal 41 is connected to the second bridge circuit BC2. In the second bridge circuit BC2, the external magnetic field H in the (−) direction acts, and the electric resistance value of the magnetoresistive effect element 27. Is below the fixed resistance value R5 of the second fixed resistance element 28 shown in FIG. 2, an ON signal is output from the second external output terminal 41. In other words, an OFF signal is always output from the first external output terminal 40 when the electric resistance value of the magnetoresistive effect element 27 exceeds the fixed resistance value R4 of the second fixed resistance element 28.

  Therefore, when the ON signal is output from the first external output terminal 40 (the OFF signal is output from the second external output terminal 41 at this time), the external magnetic field H in the (+) direction is detected by the magnetic detection device 20. When the ON signal is output from the second external output terminal 41 (in this case, the OFF signal is output from the first external output terminal 40), the external signal in the (−) direction It can be identified that the magnetic field H is acting on the magnetic detection device 20.

  As shown in FIG. 2, the fixed resistance value R3 of the first fixed resistance element 24 is affected by the electric resistance value R1 of the magnetoresistive effect element 23 when the external magnetic field H is zero and the external magnetic field H in the (+) direction. It is preferable that it is an intermediate value with respect to the maximum resistance value R2 of the magnetoresistive effect element 23. In addition, the fixed resistance value R5 of the second fixed resistance element 28 is the magnetoresistance value when the external magnetic field H is zero and the electric resistance value R1 of the magnetoresistive effect element 27 when the external magnetic field H in the (−) direction acts. It is preferably an intermediate value with respect to the maximum resistance value R4 of the effect element 27.

  Thereby, the magnetic detection apparatus 20 corresponding to bipolar detection can be realized appropriately. In addition to the above, by making the magnitude of the first interlayer coupling magnetic field Hin1 and the second interlayer coupling magnetic field Hin2 equal, the output timing of the ON signal when the external magnetic field H in the (+) direction is applied, -) The output timing of the ON signal when the external magnetic field H in the direction acts can be set to be the same.

  As shown in FIG. 1, in the magnetic detection device 20 of the present embodiment, the midpoint potential of the third series circuit 34 in which fixed resistance elements 31 and 32 are connected in series is used as the first bridge circuit BC1 and the second bridge. It is shared as the reference potential of the circuit BC2. Then, the connection between the first output extraction section 25 of the first series circuit 26 constituting the first bridge circuit BC1 and the differential amplifier 35, and the second of the second series circuit 30 constituting the second bridge circuit BC2. A first switch circuit 36 for alternately switching the connection between the output extraction unit 29 and the differential amplifier 35 is provided in the integrated circuit 22.

  As described above, the magnetic detection device 20 according to the present embodiment uses the third series circuit 34 as a common circuit in both the first bridge circuit BC1 and the second bridge circuit BC2. It is possible to reduce the number of elements.

  Furthermore, in the present embodiment, only one differential amplifier 35 is provided, and the first bridge circuit BC1 and the differential amplifier 35 are connected, and the second bridge circuit BC2 and the differential amplifier 35 are connected. Can be obtained alternately, and a differential potential can be obtained by the differential amplifier 35 from the first bridge circuit BC1 and the second bridge circuit BC2 appropriately with a simple circuit configuration.

  As described above, according to the present embodiment, the number of elements can be reduced and the circuit configuration can be simplified in the bipolar sensor.

  In the present embodiment, when the first bridge circuit BC1 and the differential amplifier 35 are connected by the first switch circuit 36, the third series circuit 26 and the ground terminal 42 are connected by the third switch circuit 48. Are connected. Further, when the second bridge circuit BC2 and the differential amplifier 35 are connected by the first switch circuit 36, the second series circuit 30 and the ground terminal 42 are connected by the third switch circuit 48. The Thus, no current flows through the second series circuit 30 when the first bridge circuit BC1 and the differential amplifier 35 are connected. Further, when the second bridge circuit BC2 and the differential amplifier 35 are connected, no current flows through the first series circuit 26. Therefore, current consumption can be reduced and detection sensitivity can be improved.

  The third switch circuit 48 is provided between the input terminal 39 and the first series circuit 26 and between the input terminal 39 and the second series circuit 30 together with the ground terminal 42 side or instead of the ground terminal 42 side. May be.

  The magnetic detection device 20 compatible with bipolar detection according to the present embodiment can be used, for example, for opening / closing detection of a folding cellular phone.

  As shown in FIG. 4, the foldable mobile phone 90 has a configuration in which a first member (display housing) 91 and a second member (operation housing) 92 are connected to each other so as to be freely opened and closed. A liquid crystal display, a receiver, and the like are provided on the surface of the first member 91 facing the second member 92. Various operation buttons, a microphone, and the like are provided on the surface of the second member 92 facing the first member 91. FIG. 4 shows a state in which the foldable mobile phone 90 is closed. As shown in FIG. 4, the first member 91 includes a magnet 94, and the second member 92 includes the magnetic detection device 20 of the present embodiment. It is built. As shown in FIG. 4, in the closed state, the magnet 94 and the magnetic detection device 20 are arranged at positions facing each other. Alternatively, the magnetic detection device 20 may be disposed at a position shifted in a direction parallel to the direction in which the external magnetic field enters from a position facing the magnet 94.

  In FIG. 4, the external magnetic field (+ H) in the (+) direction emitted from the magnet 94 is transmitted to the magnetic detection device 20, and the magnetic detection device 20 detects the external magnetic field (+ H). It is detected that the foldable mobile phone 90 is in a closed state.

  On the other hand, when the folding cellular phone 90 is opened as shown in FIG. 5, the magnitude of the external magnetic field (+ H) transmitted to the magnetic detection device 20 gradually decreases as the first member 91 moves away from the second member 92. Eventually, the external magnetic field (+ H) transmitted to the magnetic detector 20 becomes zero. When the magnitude of the external magnetic field (+ H) transmitted to the magnetic detection device 20 becomes a predetermined magnitude or less, it is detected that the foldable mobile phone 90 is in an open state, for example, the mobile phone The control unit built in 90 is controlled so that the backlight on the back side of the liquid crystal display and the operation buttons shines.

  The magnetic detection device 20 of the present embodiment is a bipolar compatible sensor. That is, in FIG. 4, the N pole of the magnet 94 is located on the left side in the figure and the S pole is located on the right side in the figure, but when the polarity is reversed as shown in FIG. 6 (N pole is on the right side in the figure and S pole is on the left side in the figure) The direction of the external magnetic field (-H) exerted on the magnetic detection device 20 is reversed from the direction of the external magnetic field (+ H) in FIG. In this embodiment, even in such a case, when the cellular phone 90 is opened as shown in FIG. 7 from the state in which the folding cellular phone 90 is closed as shown in FIG. ing.

  Therefore, since the magnet 94 can be arranged regardless of the polarity of the external magnetic field, there is no restriction on the arrangement of the magnet 94, and assembly is facilitated.

  In the above open / close detection method, even if it is not possible to identify the direction of the external magnetic field, it is only necessary to detect the change of the external magnetic field with the bipolar, so for example, either one of the external output terminals 40 and 41 shown in FIG. .

  That is, for example, when the second switch circuit 43 shown in FIG. 1 is eliminated and one signal line from the comparator 38 to the latch circuit 46 and the FET circuit 54 to the external output terminal 40 is formed, the external output terminal 40 It is possible to obtain both a detection signal for the external magnetic field in the + direction and a detection signal for the external magnetic field in the (−) direction. At this time, it is not possible to identify the direction of the external magnetic field, but there is a need to detect the direction of the external magnetic field in the open / close detection. Therefore, there is a need to identify only the direction of the external magnetic field. It may be simplified.

  Further, in the foldable mobile phone 90 of the type (turnover type) in which the first member 91 can be reversed from the opened state in FIG. 5, the camera mode is activated by the first member 91 being reversed, etc. There is a need to activate different functions in the non-inverted state and the inverted state. In this case, since the direction of the external magnetic field H acting on the magnetic detection device 20 is reversed between the non-inversion state and the inversion state, the direction of the external magnetic field is identified by the circuit configuration of FIG. That is, as already described, two external output terminals 40 and 41 are provided as shown in FIG. 1, and the first external output terminal 40 is connected to the first bridge circuit BC1 that detects the external magnetic field H in the (+) direction. The second external output terminal 41 is connected to the second bridge circuit BC2 that detects the external magnetic field H in the (−) direction. Thereby, the direction of the external magnetic field can be identified by identifying the external output terminal that outputs the ON signal.

  In FIG. 3, the right side of the drawing is described as the (+) direction, and the left side of the drawing is set as the (−) direction. However, the left side of the drawing may be set as the (−) direction, and the right side of the drawing may be set as the (+) direction. In this case, the stacked body 61 is a first stacked body in which the electric resistance changes with respect to the external magnetic field H in the (+) direction, and the stacked body 60 changes in the electrical resistance with respect to the external magnetic field H in the (−) direction. It is a 2nd laminated body. The RH curve has a line-symmetric shape with the horizontal axis shown in FIG. 2 as the axis of symmetry. That is, the electric resistances of the magnetoresistive elements 23 and 27 gradually decrease from R1 as the external magnetic field in the (+) direction increases, and gradually increase from R1 as the external magnetic field in the (−) direction increases. Become.

  The magnetic detection device 20 of the present embodiment may be used for opening / closing detection of a portable electronic device such as a game machine in addition to detection of opening / closing of a folding mobile phone. In addition to the above open / close detection, this embodiment can be used for applications that require a magnetic detection device 20 that supports bipolar detection, such as a slide sensor.

The circuit block diagram of the magnetic detection apparatus of this embodiment, RH graph for explaining the RH curve of the magnetoresistive effect element of the present embodiment; Partial sectional view showing a layer structure of the magnetoresistive effect element of the present embodiment (partial sectional view of a cut surface cut from a direction parallel to the film thickness direction), An example for explaining the use of the magnetic detection device of the present embodiment (a schematic view of a part of a foldable mobile phone incorporating the magnetic detection device, showing a state in which the phone is closed), An example for explaining the use of the magnetic detection device of the present embodiment (a partial schematic view of a foldable mobile phone incorporating the magnetic detection device, showing a state in which the phone is opened), An example for explaining the use of the magnetic detection device of the present embodiment (a schematic view of a part of a foldable mobile phone incorporating the magnetic detection device, with the arrangement of magnets reversed from that in FIG. 4 and the phone closed) Status) An example for explaining the application of the magnetic detection device of the present embodiment (a schematic view of a part of a foldable mobile phone incorporating the magnetic detection device, with the arrangement of magnets opposite to that shown in FIG. Status) An RH graph for explaining an RH curve of a magnetoresistive effect element provided in a conventional magnetic detection device;

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Magnetic detection apparatus 21 Element structure part 22 Integrated circuit 23, 27 Magnetoresistance effect element 24 1st fixed resistance element 28 2nd fixed resistance element 31, 32 Fixed resistance element 26 1st series circuit 30 2nd series circuit 34 3rd series Circuit 35 Differential amplifier 36 First switch circuit 38 Comparator 40, 41 External output terminal 43 Second switch circuit 48 Third switch circuit 60 First stacked body 61 Second stacked body 63 Seed layer 64 First antiferromagnetic layer 65 First 1 fixed magnetic layer 66 first nonmagnetic material layer 67 first free magnetic layer 68 intermediate separation layer 69 second free magnetic layer 70 second nonmagnetic material layer 71 second fixed magnetic layer 72 second antiferromagnetic layer 73 protective layer 90 Foldable mobile phone 91 First member (display housing)
92 Second member (operation housing)
94 Magnet C1 First RH curve C2 Second RH curve Hin1 First interlayer coupling magnetic field Hin2 Second interlayer coupling magnetic field

Claims (5)

It has a magnetoresistive effect element using a magnetoresistive effect whose electric resistance changes with respect to an external magnetic field,
The magnetoresistive effect element has a laminated structure of a first laminated body and a second laminated body,
The first laminate has a configuration in which a first pinned magnetic layer and a first free magnetic layer are laminated via a first nonmagnetic material layer, and an electric resistance changes with respect to an external magnetic field in the (+) direction. ,
The second stacked body has a configuration in which a second pinned magnetic layer and a second free magnetic layer are stacked via a second nonmagnetic material layer, and is in a (−) direction opposite to the (+) direction. The electrical resistance changes with respect to the external magnetic field,
When the external magnetic field in the (+) direction enters, the external magnetic field in the (+) direction is detected by changing the electric resistance value of the first laminate, and the external magnetic field in the (−) direction enters. When this is done, the external magnetic field in the (−) direction is detected by changing the electric resistance value of the second laminate. On the RH graph, the horizontal axis is the magnitude of the external magnetic field H and the vertical axis is the resistance value R of the magnetoresistive element.
A first interlayer coupling magnetic field Hin1 acting between the first pinned magnetic layer and the first free magnetic layer appears on the external magnetic field side in the (+) direction, and between the second pinned magnetic layer and the second free magnetic layer. The acting second interlayer coupling magnetic field Hin2 appears on the external magnetic field side in the (−) direction,
When the electric resistance value of the magnetoresistive effect element when the external magnetic field is zero is used as a reference, the increase / decrease tendency of the electric resistance value of the magnetoresistive effect element with respect to the change in the intensity of the external magnetic field in the (+) direction; The magnetic detection apparatus according to claim 1, wherein an increasing / decreasing tendency of the electric resistance value of the magnetoresistive effect element with respect to a change in strength of an external magnetic field in a direction shows a reverse tendency. Two magnetoresistive effect elements are prepared, one magnetoresistive effect element is connected in series to the first fixed resistance element via the first output extraction unit, and the other magnetoresistive effect element is the second output extraction. Connected in series to the second fixed resistance element through the section,
The fixed resistance value R3 of the first fixed resistance element is equal to the electric resistance value R1 of the magnetoresistive effect element when the external magnetic field is zero and the external magnetic field is zero when the external magnetic field in the (+) direction acts. A value between the electric resistance value R2 of the magnetoresistive effect element and the electric resistance value R2 of the magnetoresistive effect element that has changed to the maximum from the electric resistance value R1. The electric resistance value R1 when the magnetic field is zero and the electric resistance of the magnetoresistive effect element changed to the maximum from the electric resistance value R1 when the external magnetic field is zero when an external magnetic field in the (−) direction is applied. The magnetic detection device according to claim 2, wherein the magnetic detection device has a value between the resistance value R4.   The fixed resistance value R3 of the first fixed resistance element is an intermediate value between the electric resistance value R1 and the electric resistance value R2 of the magnetoresistive effect element, and the fixed resistance value R5 of the second fixed resistance element is the magnetic resistance value R5. 4. The magnetic detection device according to claim 3, wherein the magnetic detection device has an intermediate value between an electric resistance value R1 and an electric resistance value R4 of the resistance effect element. A first series circuit in which the magnetoresistive effect element and the first fixed resistance element are connected in series, a second series circuit in which the magnetoresistive effect element and the second fixed resistance element are connected in series, and the fixed resistance element is the third A third series circuit connected in series via the output extraction unit,
One of the first output extraction unit of the first series circuit and the second output extraction unit of the second series circuit are respectively connected to a common differential output unit via a connection switching unit. Connected together with
In the connection switching unit, when the first output extraction unit and the differential output unit are connected, the first bridge circuit formed by connecting the first series circuit and the third series circuit in parallel is the difference. When the second output extraction unit and the differential output unit are connected in the connection switching unit, the second series circuit and the third series circuit are switched to the state connected to the dynamic output unit. 5. The magnetic detection device according to claim 3, wherein the second bridge circuit connected in parallel is switched to a state of being connected to the differential output unit. 6.

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