Patent Publication Number: US-2022214401-A1

Title: Magnetic sensor and inspection device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-000054, filed on Jan. 4, 2021; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a magnetic sensor and an inspection device. 
     BACKGROUND 
     There is a magnetic sensor that uses a magnetic layer. There is an inspection device that uses the magnetic sensor. It is desirable to increase the sensitivity of the magnetic sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 1C  are schematic views illustrating a magnetic sensor according to a first embodiment; 
         FIG. 2  is a schematic cross-sectional view illustrating a portion of the magnetic sensor according to the first embodiment; 
         FIGS. 3A to 3C  are schematic views illustrating a magnetic sensor according to the first embodiment; 
         FIG. 4  is a graph illustrating a characteristic of the magnetic sensor; 
         FIG. 5  is a graph illustrating a characteristic of the magnetic sensor; 
         FIGS. 6A to 6C  are schematic views illustrating a magnetic sensor according to the first embodiment; 
         FIGS. 7A and 7B  are schematic views illustrating a magnetic sensor according to the first embodiment; 
         FIG. 8  is a schematic cross-sectional view illustrating the magnetic sensor according to the first embodiment; 
         FIGS. 9A and 9B  are graphs illustrating characteristics of the magnetic sensor according to the first embodiment; 
         FIGS. 10A to 10C  are graphs illustrating characteristics of the magnetic sensor according to the first embodiment; 
         FIGS. 11A and 11B  are schematic views illustrating a magnetic sensor according to a second embodiment; 
         FIGS. 12A and 12B  are schematic cross-sectional views illustrating the magnetic sensor according to the second embodiment; 
         FIGS. 13A and 13B  are schematic views illustrating a magnetic sensor according to the second embodiment; 
         FIGS. 14A and 14B  are schematic cross-sectional views illustrating the magnetic sensor according to the second embodiment; 
         FIG. 15  is a schematic view illustrating a magnetic sensor according to a third embodiment; 
         FIG. 16  is a schematic view illustrating the magnetic sensor according to the third embodiment; 
         FIGS. 17A to 17C  are schematic views illustrating the magnetic sensor according to the third embodiment; 
         FIG. 18  is a schematic view illustrating an inspection device according to a fourth embodiment; 
         FIG. 19  is a schematic view illustrating an inspection device according to the third embodiment; 
         FIG. 20  is a schematic perspective view showing an inspection device according to the fourth embodiment; 
         FIG. 21  is a schematic plan view showing the inspection device according to the fourth embodiment; 
         FIG. 22  is a schematic view showing the magnetic sensor and the inspection device according to the fourth embodiment; and 
         FIG. 23  is a schematic view showing the inspection device according to the fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a magnetic sensor includes a first sensor part. The first sensor part includes a first magnetic member, a first counter magnetic member, and a first magnetic element. A direction from the first magnetic member toward the first counter magnetic member is along a first direction. The first magnetic element includes one or a plurality of first extension parts. The first extension part includes a first magnetic layer, a first counter magnetic layer, and a first nonmagnetic layer. The first magnetic layer includes a first portion, a first counter portion, and a first middle portion. A direction from the first portion toward the first counter portion is along the first direction. The first middle portion is between the first portion and the first counter portion. The first nonmagnetic layer is between the first counter magnetic layer and at least a portion of the first middle portion in a second direction crossing the first direction. 
     According to one embodiment, an inspection device includes the magnetic sensor described above, and a processor configured to process a signal output from the magnetic sensor. 
     Various embodiments are described below with reference to the accompanying drawings. 
     The drawings are schematic and conceptual; and the relationships between the thickness and width of portions, the proportions of sizes among portions, etc., are not necessarily the same as the actual values. The dimensions and proportions may be illustrated differently among drawings, even for identical portions. 
     In the specification and drawings, components similar to those described previously or illustrated in an antecedent drawing are marked with like reference numerals, and a detailed description is omitted as appropriate. 
     First Embodiment 
       FIGS. 1A to 1C  are schematic views illustrating a magnetic sensor according to a first embodiment.  FIG. 1A  is a line Al-A 2  cross-sectional view of  FIG. 13 .  FIG. 13  is a plan view.  FIG. 1C  is a cross-sectional view. 
     As shown in  FIGS. 1A and 1B , the magnetic sensor  110  according to the embodiment includes a first sensor part  10 k The first sensor part  10 A includes a first magnetic member  51 , a first counter magnetic member  51 A, and a first magnetic element  11 E. 
     The direction from the first magnetic member  51  toward the first counter magnetic member  51 A is along a first direction. The first direction is taken as an X-axis direction. One direction perpendicular to the X-axis direction is taken as a Z-axis direction. A direction perpendicular to the Z-axis direction and the X-axis direction is taken as a Y-axis direction. 
     The first magnetic element  11 E includes one or multiple first extension parts  11   x.  In the example, the number of the first extension parts  11   x  is 1, As shown in  FIGS. 1A and 1C , the first extension part  11   x  includes a first magnetic layer  11 , a first counter magnetic layer  11   o,  and a first nonmagnetic layer  11   n.    
     As shown in  FIGS. 1A and 1B , the first magnetic layer  11  includes a first portion p 1 , a first counter portion pA 1 , and a first middle portion pM 1 . 
     The direction from the first portion p 1  toward the first counter portion pA 1  is along the first direction (the X-axis direction). The first middle portion pM 1  is between the first portion p 1  and the first counter portion pA 1 . The first nonmagnetic layer  11   n  is between the first counter magnetic layer  11   o  and at least a portion of the first middle portion pM 1  in a second direction. The second direction crosses the first direction. The second direction is, for example, the Z-axis direction. The direction from the first portion p 1  toward the first magnetic member  51  is along the second direction. The direction from the first counter portion pA 1  toward the first counter magnetic member  51 A is along the second direction. 
     As shown in  FIG. 1A , the first sensor part  10 A may further include a first insulating member  65   a.  At least a portion of the first insulating member  65   a  is between the first portion p 1  and the first magnetic member  51  and between the first counter portion pA 1  and the first counter magnetic member  51 A. The first insulating member  65   a  may be located around the first magnetic element  11 E, the first magnetic member  51 , and the first counter magnetic member  51 A. The first insulating member  65   a  is not illustrated in  FIG. 1B . 
     As shown in  FIG. 1A , for example, the position in the first direction (the X-axis direction) of the first nonmagnetic layer  11   n  is between the position in the first direction of the first magnetic member  51  and the position in the first direction of the first counter magnetic member  51 A. In the second direction (the Z-axis direction), the first nonmagnetic layer  11   n  overlaps a region  66   a  between the first magnetic member  51  and the first counter magnetic member  51 A. The region  66   a  may be, a portion of the first insulating member  65   a.    
     The first middle portion pM 1 , the first nonmagnetic layer  11   n,  and the first counter magnetic layer  11   o  of the first magnetic layer  11  are used as, for example, a detecting part. The electrical resistance of the detecting part changes according to a magnetic field of a detection object. The detecting part is, for example, a MTJ (Magnetic Tunnel Junction) element. 
     According to the embodiment, a magnetic field (the external magnetic field of the detection object) is concentrated by the first magnetic member  51  and the first counter magnetic member  51 A. The concentrated magnetic field can be efficiently applied to the detecting part (e.g., the MTJ element). For example, the first magnetic member  51  and the first counter magnetic member  51 A function as a MFC (Magnetic Field Concentrator). 
     According to the embodiment, the first portion p 1  of the first magnetic layer  11  overlaps the first magnetic member  51  in the Z-axis direction. The first counter portion pA 1  of the first magnetic layer  11  overlaps the first counter magnetic member  51 A in the Z-axis direction. Thereby, the concentrated magnetic field (external magnetic field) is efficiently applied to the first portion p 1  and the first counter portion pA 1 . The concentrated magnetic field is more effectively applied to the detecting part. High sensitivity is obtained thereby. According to the embodiment, for example, a magnetic sensor can be provided in which the sensitivity can be increased. 
     For example, the external magnetic field includes a component along the X-axis direction. The orientation of the magnetization of the first magnetic layer  11  is changed by the external magnetic field. For example, when the external magnetic field is 0, the angle between the magnetization of the first magnetic layer  11  and the magnetization of the first counter magnetic layer  11   o  is substantially 0. At this time, for example, these magnetizations are along the Y-axis direction. The electrical resistance of the detecting part at this time is low. On the other hand, the angle between the magnetization of the first magnetic layer  11  and the magnetization of the first counter magnetic layer  11   o  increases when the external magnetic field is not 0. The electrical resistance at this time is high. 
     A first conductive layer  11 L may be provided as shown in  FIG. 1A . The first counter magnetic layer  11   o  is located between the first middle portion pM 1  and the first conductive layer  11 L. The first conductive layer  11 L is electrically connected with the first counter magnetic layer  11   o.    
     In the example as shown in  FIG. 1B , the first extension part  11   x  includes a second counter magnetic layer  12   o  and a second nonmagnetic layer  12   n.  In the example, the first nonmagnetic layer  11   n  is between the first counter magnetic layer  11   o  and a portion of the first middle portion pM 1  in the second direction (the Z-axis direction). The second nonmagnetic layer  12   n  is between the second counter magnetic layer  12   o  and another portion of the first middle portion pM 1  in the second direction. The direction from the second nonmagnetic layer  12   n  toward the first nonmagnetic layer  11   n  is along a third direction. The third direction crosses a plane (the Z-X plane) including the first and second directions. The third direction is, for example, the Y-axis direction. The second counter magnetic layer  12   o,  the second nonmagnetic layer  12   n,  and the other portion of the first middle portion pM 1  are one detecting part (e.g., the MTJ element). 
     Another first conductive layer  11 L that is electrically connected with the second counter magnetic layer  12   o  also may be provided. 
     The electrical resistance of the first magnetic element  11 E corresponds to the electrical resistance of a current path that includes the first counter magnetic layer  11   o,  the first nonmagnetic layer  11   n,  the first magnetic layer  11 , the second nonmagnetic layer  12   n,  and the second counter magnetic layer  12   o.  The electrical resistance of the first magnetic element  11 E corresponds to the electrical resistance between the first conductive layer  11 L electrically connected with the first counter magnetic layer  11   o  and the other first conductive layer  11 L electrically connected with the second counter magnetic layer  12   o.    
     As shown in  FIG. 1C , for example, one end  11 Ee of the first magnetic element  11 E corresponds to the other first conductive layer  11 L described above. For example, another end  11 Ef of the first magnetic element  11 E corresponds to the first conductive layer  11 L described above. 
     As shown in  FIG. 1B , the magnetic sensor  110  may include an element current circuit  75 . The element current circuit  75  is configured to supply an element current Id to the first magnetic element  11 E. For example, the element current circuit  75  is electrically connected with the one end  11 Ee of the first magnetic element  11 E and the other end  11 Ef of the first magnetic element  11 E. For example, the element current circuit  75  supplies the element current Id to a current path between the one end  11 Ee of the first magnetic element  11 E and the other end  11 Ef of the first magnetic element  11 E. The electrical resistance of the first magnetic element  11 E can be detected using the element current Id. The element current circuit  75  may be included in a controller  70 . 
     As shown in  FIG. 1A , the length along the first direction (the X-axis direction) of the first magnetic layer  11  is taken as a first magnetic layer length L 11 . The distance along the first direction between the first magnetic member  51  and the first counter magnetic member  51 A is taken as a first distance g 1 . For example, it is favorable for the first magnetic layer length L 11  to be not less than 2 times the first distance g 1 . Thereby, as described below, the magnetic field of the detection object is more efficiently applied to the detecting part. Higher sensitivity is obtained. 
     The length along the first direction (the X-axis direction) of the first nonmagnetic layer  11   n  is taken as a first nonmagnetic layer length L 11   n.  It is favorable for the first nonmagnetic layer length L 11   n  to be, for example, not more than the first distance g 1 . Higher sensitivity is easily obtained thereby. 
     The length along the first direction (the X-axis direction) of the first portion p 1  is taken as a first portion length Lp 1 . The first portion length Lp 1  corresponds to the length of a region that overlaps the first magnetic member  51  of the first magnetic layer  11 . In one example, it is favorable for the first portion length Lp 1  to be greater than the first distance g 1 . High sensitivity is easily obtained. The length along the first direction (the X-axis direction) of the first counter portion pA 1  is taken as a first counter portion length LpA 1 . The first counter portion length LpA 1  corresponds to the length of a region that overlaps the first counter magnetic member  51 A of the first magnetic layer  11 . In one example, it is favorable for the first counter portion length LpA 1  to be greater than the first distance g 1 . High sensitivity is easily obtained. 
     As shown in  FIG. 1A , the distance along the second direction (the Z-axis direction) between the first portion p 1  and the first magnetic member  51  is taken as a distance d 1 . It is favorable for the distance d 1  to be, for example, less than the first distance g 1 . It is favorable for the distance d 1  to be, for example, not more than the length (the first portion length Lp 1 ) along the first direction (the X-axis direction) of the first portion p 1 . Higher sensitivity is easily obtained. 
     It is favorable for the distance d 1  to be, for example, not less than 2 nm. The electrical insulation between the first magnetic layer  11  and the first magnetic member  51  is made more reliable thereby. The electrical insulation between the first magnetic layer  11  and the first counter magnetic member  51 A becomes more reliable. The distance d 1  may be, for example, not less than 10 nm. 
       FIG. 2  is a schematic cross-sectional view illustrating a portion of the magnetic sensor according to the first embodiment. 
     The first extension part lix may further include a first layer  11   r.  The first layer  11   r  includes at least one selected from the group consisting of IrMn and PtMn. The first layer  11   r  is, for example, an antiferromagnetic layer. The first counter magnetic layer  11   o  is located between the first magnetic layer  11  (the first middle portion pM 1 ) and the first layer  11   r.    
     In the example, the first extension part  11   x  includes a magnetic film  11   q  and a nonmagnetic film  11   p.  The magnetic film  11   q  is between the first counter magnetic layer  11   o  and the first layer  11   r.  The nonmagnetic film  11   p  is between the first counter magnetic layer  11   o  and the magnetic film  11   q.  The nonmagnetic film  11   p  includes, for example, Ru. A layer PL that includes the first counter magnetic layer  11   o,  the nonmagnetic film  11   p,  and the magnetic film  11   q  functions as a reference layer. The layer PL is, for example, a fixed magnetic layer. The magnetization of the first magnetic layer  11  easily changes. The first magnetic layer  11  is, for example, a free magnetic layer. 
     The first nonmagnetic layer  11   n  includes, for example, MgO. A high MR ratio is obtained. The first magnetic layer  11 , the first counter magnetic layer  11   o,  and the magnetic film  11   q  include, for example, at least one selected from the group consisting of Fe, Co, and Ni. The first magnetic layer  11 , the first counter magnetic layer  11   o,  and the magnetic film  11   q  are, for example, ferromagnetic layers. The first magnetic member  51  and the first counter magnetic member  51 A include, for example, at least one selected from the group consisting of NiFe and FeAlSi. The first magnetic member  51  and the first counter magnetic member  51 A are, for example, soft magnetic materials. The relative magnetic permeabilities of the first magnetic member  51  and the first counter magnetic member  5 A are, for example, not less than 1000. 
       FIGS. 3A to 3C  are schematic views illustrating a magnetic sensor according to the first embodiment.  FIG. 3A  is a line A 1 -A 2  cross-sectional view of  FIG. 36 .  FIG. 3B  is a plan view.  FIG. 3C  is a cross-sectional view. 
     As shown in  FIGS. 3A and 3B , in the magnetic sensor  111  according to the embodiment as well, the first sensor part  10 A includes the first magnetic member  51 , the first counter magnetic member  51 A, and the first magnetic element  11 E. In the magnetic sensor  111  as shown in  FIG. 3B , the first magnetic element  11 E includes the multiple first extension parts  11   x.    
     The multiple first extension parts lix are arranged in the third direction. The third direction crosses a plane (the X-Z plane) including the first and second directions. The third direction is, for example, the Y-axis direction. 
     As shown in  FIG. 3C , the direction from the first nonmagnetic layer  11   n  of one of the multiple first extension parts  11   x  toward the first nonmagnetic layer  11   n  of another one of the multiple first extension parts  11   x  is along the third direction (the Y-axis direction). 
     As shown in  FIGS. 3B and 3C , the first magnetic element  11 E may further include a first connection member CN 1 . For example, one first conductive layer  11 L may be used as the first connection member CN 1 . The first connection member CN 1  electrically connects the second counter magnetic layer  12   o  of one of the multiple first extension parts  11   x  and the first counter magnetic layer  11   o  of another one of the multiple first extension parts  11   x.    
     For example, the detecting parts that are included in the multiple first extension parts  11   x  are electrically connected in series. For example, noise is suppressed. For example, an electrical resistance that is suited to the detection is obtained. Higher sensitivity is easily obtained. 
     Examples of characteristics of the magnetic sensor will now be described. 
       FIG. 4  is a graph illustrating a characteristic of the magnetic sensor. 
       FIG. 4  illustrates simulation results of a characteristic when the length (the first magnetic layer length L 11 ) along the X-axis direction of the first magnetic layer  11  is changed. In the model of the simulation, the distance (the first distance g 1 ) between the first magnetic member  51  and the first counter magnetic member  51 A is 5 μm. The length (the first nonmagnetic layer length L 11   n ) along the X-axis direction of the first nonmagnetic layer  11   n  is 4 μm. When the first magnetic layer length L 11  is 4 μm, the length of the first magnetic layer  11  is equal to the length of the first nonmagnetic layer  11   n.  The first magnetic layer length L 11  is modified in such a model. In this model, the region that includes the interface between the first nonmagnetic layer  11   n  and the first magnetic layer  11  corresponds to a sensitive part. The length of the first magnetic layer  11  may be increased or reduced without changing the length of the sensitive part. 
     The horizontal axis of  FIG. 4  is the first magnetic layer length L 11 . The vertical axis is an average magnetic flux density BP at the position of the interface between the first middle portion pill and the first nonmagnetic layer  11   n.  The magnetic flux density BP is normalized to have a value of 1 when the first magnetic layer length L 11  is 4 μm. The magnetic flux density BP corresponds to the sensitivity of the detection of the external magnetic field. 
     As shown in  FIG. 4 , the magnetic flux density BP increases as the first magnetic layer length L 11  increases. 
     According to the embodiment, for example, it is favorable for the first magnetic layer length L 11  to be not less than 2 times the first distance g 1 . Thereby, the magnetic field of the detection object is the more efficiently applied to the detecting part. Higher sensitivity is obtained. 
       FIG. 5  is a graph illustrating a characteristic of the magnetic sensor. 
     In the model of the simulation of  FIG. 5 , the lengths in the X-axis direction of the first nonmagnetic layer  11   n  and the first counter magnetic layer  11   o  are equal to the length (the first magnetic layer length L 11 ) in the X-axis direction of the first magnetic layer  11 . The lengths in the X-axis direction of the first nonmagnetic layer  11   n  and the first counter magnetic layer  11   o  change conjunctively with the change of the first magnetic layer length L 11 . In the model of the simulation, the first distance g 1  is 5 μm. In the model of  FIG. 5  as well, a region that includes the interface between the first nonmagnetic layer  11   n  and the first magnetic layer  11  corresponds to the sensitive part. In the model of  FIG. 5 , the length of the sensitive part changes conjunctively according to the change of the first magnetic layer length L 11 . 
     The horizontal axis of  FIG. 5  is the first magnetic layer length L 11 . The vertical axis is the average magnetic flux density BP at the position of the interface between the first middle portion pM 1  and the first nonmagnetic layer  11   n.  The magnetic flux density BP is normalized to have a value of 1 when the first magnetic layer length L 11  is 4 μm. 
     In this model as shown in  FIG. 5 , the magnetic flux density BP decreases when the first magnetic layer length L 11  becomes excessively long. This is caused by the length of the sensitive part increasing conjunctively with the increase of the first magnetic layer length L 11 . 
     As described above, it is favorable to maintain a short length in the X-axis direction of the first nonmagnetic layer  11   n  and for the length in the X-axis direction of the first magnetic layer  11  to be long. A high magnetic flux density BP is obtained thereby. For example, high sensitivity is obtained. 
       FIGS. 6A to 6C  are schematic views illustrating a magnetic sensor according to the first embodiment.  FIG. 6A  is a line A 1 -A 2  cross-sectional view of  FIG. 6B .  FIG. 6B  is a plan view.  FIG. 6C  is a cross-sectional view. 
     In the magnetic sensor  112  according to the embodiment as shown in  FIGS. 6A and 6B , the first sensor part  10 A includes a first conductive member  21  in addition to the first magnetic member  51 , the first counter magnetic member  51 A, and the first magnetic element  11 E. Otherwise, the configuration of the magnetic sensor  112  may be similar to the configuration of the magnetic sensor  110 . 
     In the second direction (the Z-axis direction), at least a portion of the first conductive member  21  overlaps the region  66   a  between the first magnetic member  51  and the first counter magnetic member  51 A. A first current I 1  that includes an alternating current component can flow in the first conductive member  21 . The first current I 1  flows through the first conductive member  21  along the third direction. The third direction crosses a plane (the Z-X plane) including the first and second directions. The third direction is, for example, the Y-axis direction. 
     The magnetic sensor  112  may include a first current circuit  71 . The first current circuit  71  is configured to supply the first current Z 1  to the first conductive member  21 . The first current circuit  71  may be included in the controller  70 . 
     For example, the first current circuit  71  is electrically connected to one end  21   e  of the first conductive member  21  and another end  21   f  of the first conductive member  21 . The first current I 1  flows between the one end  21   e  and the other end  21   f.    
     By the first current I 1  that includes the alternating current component flowing in the first conductive member  21 , a magnetic field (an alternating current magnetic field) that is based on the first current I 1  is applied to the detecting part of the first magnetic element  11 E. The alternating current magnetic field includes, for example, a component along the X-axis direction. The alternating current magnetic field is concentrated by the first magnetic member  51  and the first counter magnetic member  51 A. The concentrated alternating current magnetic field is applied to the detecting part. The alternating current magnetic field is efficiently applied to the detecting part. As described below, unnecessary noise is suppressed by using the alternating current magnetic field. Higher sensitivity is obtained. 
       FIGS. 7A and 7B  are schematic views illustrating a magnetic sensor according to the first embodiment. 
       FIG. 7A  is a line A 1 -A 2  cross-sectional view of  FIG. 7B .  FIG. 7B  is a plan view. 
       FIG. 8  is a schematic cross-sectional view illustrating the magnetic sensor according to the first embodiment. 
     In the magnetic sensor  113  according to the embodiment as shown in  FIGS. 7A and 7B , the first sensor part  10 A includes the first conductive member  21  in addition to the first magnetic member  51 , the first counter magnetic member  51 A, and the first magnetic element  11 E. Otherwise, the configuration of the magnetic sensor  113  may be similar to the configuration of the magnetic sensor  111 . For example, the magnetic sensor  113  includes the multiple first extension parts  11   x  as shown in  FIGS. 7A and 8 . 
     In the magnetic sensor  113  as well, in the second direction (the Z-axis direction), at least a portion of the first conductive member  21  overlaps the region  66   a  between the first magnetic member  51  and the first counter magnetic member  51 A. The first current I 1  that includes an alternating current component can flow in the first conductive member  21  along the third direction (the Y-axis direction). The alternating current magnetic field that is based on the first current I 1  is concentrated by the first magnetic member  51  and the first counter magnetic member  51 A. The concentrated alternating current magnetic field is efficiently applied to the detecting part. Higher sensitivity is obtained. 
     In the magnetic sensor (e.g., the magnetic sensors  110  to  113 , etc.) according to the first embodiment, the electrical resistance of the first magnetic element  11 E has an even-function characteristic with respect to the magnetic field applied to the first magnetic element  11 E. The magnetic field includes, for example, an external magnetic field of the detection object. The magnetic field may include a magnetic field (an alternating current magnetic field) based on the first current I 1  including the alternating current component. For example, the electrical resistance of the first magnetic element  11 E has an even-function characteristic with respect to the first current I 1  supplied to the first conductive member  21 . As described above, the magnetic field includes a component along the X-axis direction. 
     An example of the electrical resistance of the first magnetic element  11 E will now be described. 
       FIGS. 9A and 9B  are graphs illustrating characteristics of the magnetic sensor according to the first embodiment. 
     The horizontal axis of  FIG. 9A  is the intensity of an external magnetic field Hex applied to the first magnetic element  11 E. The vertical axis of  FIG. 9A  is an electrical resistance Rx of the first magnetic element  11 E. For example, the electrical resistance Rx corresponds to the electrical resistance between the one end  11 lEe of the first magnetic element  11 E and the other end  11 Ef of the first magnetic element  11 E.  FIG. 9A  corresponds to an R-H characteristic. The external magnetic field Hex has an X-axis direction component. 
     As shown in  FIG. 9A , the electrical resistance Rx has an even-function characteristic with respect to the external magnetic field Hex. For example, the electrical resistance Rx of the first magnetic element  11 E has a first value R 1  when a first magnetic field Hex 1  is applied to the first magnetic element  11 E. The electrical resistance Rx has a second value R 2  when a second magnetic field Hex 2  is applied to the first magnetic element  11 E. The electrical resistance Rx has a third value R 3  when a third magnetic field Hex 3  is applied to the first magnetic element  11 E. The absolute value of the first magnetic field Hex 1  is less than the absolute value of the second magnetic field Hex 2  and less than the absolute value of the third magnetic field Hex 3 . The orientation of the second magnetic field Hex 2  is opposite to the orientation of the third magnetic field Hex 3 . The first value R 1  is less than the second value R 2  and less than the third value R 3 . 
     For example, the first magnetic field Hex 1  is substantially 0. The electrical resistance Rx has a fourth value R 4  when the external magnetic field Hex is not applied to the first magnetic element  11 E. The first value R 1  may be substantially equal to the fourth value R 4  when the external magnetic field Hex is not applied. For example, the ratio of the absolute value of the difference between the first value R 1  and the fourth value R 4  to the fourth value R 4  is not more than 0.01. The ratio may be not more than 0.001. A substantially even-function characteristic is obtained for the positive and negative external magnetic fields. 
     The horizontal axis of  FIG. 9B  is the first current II that is supplied to the first conductive member  21 . The vertical axis of  FIG. 9B  is the electrical resistance Rx of the first magnetic element  11 E. As shown in  FIG. 9B , the electrical resistance Rx has an even-function characteristic with respect to the first current I 1 . 
     For example, the electrical resistance Rx of the first magnetic element  11 E has the first value R 1  when a first-value current Ia 1  is supplied to the first conductive member  21 . The electrical resistance Rx has the second value R 2  when a second-value current Ia 2  is supplied to the first conductive member  21 . The electrical resistance Rx has the third value R 3  when a third-value current Ia 3  is supplied to the first conductive member  21 . The absolute value of the first-value current Ia 1  is less than the absolute value of the second-value current Ia 2  and less than the absolute value of the third-value current Ia 3 . For example, the first-value current Ia 1  may be substantially 0. The orientation of the second-value current Ia 2  is opposite to the orientation of the third-value current Ia 3 . 
     For example, the first-value current Ia 1  is substantially 0. For example, the electrical resistance Rx is the fourth value R 4  when a current does not flow to the first conductive member  21 . For example, the first value R 1  is substantially equal to the fourth value R 4  when a current does not flow. For example, the ratio of the absolute value of the difference between the first value R 1  and the fourth value R 4  to the fourth value R 4  is not more than 0.01. The ratio may be not more than 0.001. A substantially even-function characteristic is obtained for the positive and negative currents. 
     By utilizing such an even-function characteristic, highly-sensitive detection is possible as follows. 
     An example will now be described in which the first current I 1  is an alternating current and substantially does not include a direct current component. The first current I 1  (the alternating current) is supplied to the first conductive member  21 ; and an alternating current magnetic field due to the alternating current is applied to the first magnetic element  11 E. An example of the change of the electrical resistance Rx at this time will be described. 
       FIGS. 10A to 10C  are graphs illustrating characteristics of the magnetic sensor according to the first embodiment. 
       FIG. 10A  shows characteristics when a signal magnetic field Hsig (an external magnetic field) applied to the first magnetic element  11 E is 0.  FIG. 10B  shows characteristics when the signal magnetic field Hsig is positive.  FIG. 10C  shows characteristics when the signal magnetic field Hsig is negative. These figures show the relationship between a magnetic field H and a resistance R (corresponding to the electrical resistance Rx). 
     As shown in  FIG. 10A , when the signal magnetic field Hsig is 0, the resistance R has a characteristic that is symmetric with respect to the positive and negative magnetic field H. When an alternating current magnetic field Hac is zero, the resistance R is a low resistance Ro. For example, the magnetization of the free magnetic layer is rotated substantially identically to the positive and negative magnetic field H. Therefore, a symmetric resistance change is obtained. The change of the resistance R with respect to the alternating current magnetic field Hac has the same value between the positive and negative polarities. The period of the change of the resistance R is ½ times the period of the alternating current magnetic field Hac. The change of the resistance R substantially does not include the frequency component of the alternating current magnetic field Hac. 
     As shown in  FIG. 10B , the characteristic of the resistance R shifts to the positive magnetic field H side when a positive signal magnetic field Hsig is applied. For example, the resistance R becomes high for the alternating current magnetic field Hac on the positive side. The resistance R becomes low for the alternating current magnetic field Hac on the negative side. 
     As shown in  FIG. 10C , the characteristic of the resistance R shifts to the negative magnetic field H side when a negative signal magnetic field Hsig is applied. For example, the resistance R becomes low for the alternating current magnetic field Hac on the positive side. The resistance R becomes high for the alternating current magnetic field Hac on the negative side. 
     Change in the resistance R is different for the positive and negative of the alternating current magnetic field Hac when a signal magnetic field Hsig with non-zero magnitude is applied. The period of the change of the resistance R with respect to the positive and negative of the alternating current magnetic field Hac is equal to the period of the alternating current magnetic field Hac. An output voltage that has an alternating current frequency component corresponding to the signal magnetic field Hsig is generated. 
     The characteristics described above are obtained in the case where the signal magnetic field Hsig does not temporally change. The case where the signal magnetic field Hsig temporally changes is as follows. The frequency of the signal magnetic field Hsig is taken as a signal frequency fsig. The frequency of the alternating current magnetic field Hac is taken as an alternating current frequency fac. In such a case, an output that corresponds to the signal magnetic field Hsig is generated at the frequency of fac±fsig. 
     In the case where the signal magnetic field Hsig temporally changes, the signal frequency fsig is, for example, not more than 1 kHz. On the other hand, the alternating current frequency fac is sufficiently greater than the signal frequency fsig. For example, the alternating current frequency fac is not less than 10 times the signal frequency fsig. 
     For example, the signal magnetic field Hsig can be detected with high accuracy by extracting an output voltage having the same period (frequency) component (alternating current frequency component) as the period (the frequency) of the alternating current magnetic field Hac. In the magnetic sensor (the magnetic sensor  112  or the magnetic sensor  113 ) according to the embodiment, the external magnetic field Hex (the signal magnetic field Hsig) that is the detection object can be detected with high sensitivity by utilizing such characteristics According to the embodiment, the external magnetic field Hex (the signal magnetic field Hsig) and the alternating current magnetic field Hac due to the first current I 1  can be efficiently applied to the first magnetic element  11 E by the first magnetic member  51  and the first counter magnetic member  51 A. High sensitivity is obtained. 
     Second Embodiment 
       FIGS. 11A and 11B  are schematic views illustrating a magnetic sensor according to a second embodiment. 
       FIG. 11A  is a line A 1 -A 2  cross-sectional view of  FIG. 11B .  FIG. 11B  is a plan view. 
       FIGS. 12A and 12B  are schematic cross-sectional views illustrating the magnetic sensor according to the second embodiment. 
     As shown in  FIGS. 11A and 11B , the magnetic sensor  114  according to the embodiment includes the first sensor part  10 A. The first sensor part  10 A further includes another first counter magnetic member  51 B in addition to the first magnetic member  51 , the first counter magnetic member  51 A, and the first magnetic element  11 E. 
     The first counter magnetic member  51 A is between the first magnetic member  51  and the other first counter magnetic member  51 B in the first direction (the X-axis direction). 
     As shown in  FIG. 11A , the first extension part  11   x  further includes the second counter magnetic layer  12   o  and the second nonmagnetic layer  12   n  in addition to the first magnetic layer  11 , the first counter magnetic layer  11   o,  and the first nonmagnetic layer  11   n.  The first magnetic layer  11  further includes a second counter portion pA 2  and a second middle portion pM 2  in addition to the first portion p 1 , the first counter portion pA 1 , and the first middle portion pM 1 . The first counter portion pA 1  is between the first portion p 1  and the second counter portion pA 2  in the first direction (the X-axis direction). The second middle portion pM 2  is between the first counter portion pA 1  and the second counter portion pA 2 . 
     As shown in  FIG. 11A , the first nonmagnetic layer  11   n  is between the first counter magnetic layer  11   o  and at least a portion of the first middle portion pM 1  in the second direction (the Z-axis direction). As shown in  FIG. 11A , the second nonmagnetic layer  12   n  is between the second counter magnetic layer  12   o  and at least a portion of the second middle portion pM 2  in the second direction (the Z-axis direction). 
     The electrical resistance of the first magnetic element  11 E corresponds to the electrical resistance of a current path that includes the first magnetic layer  11 , the first counter magnetic layer  11   o,  the first nonmagnetic layer  11   n,  the second nonmagnetic layer  12   n,  and the second counter magnetic layer  12   o.    
     In the example as shown in  FIG. 11B , the first magnetic element  11 E includes the multiple first extension parts lix and the first connection member CN 1 . The multiple first extension parts lix are arranged along the third direction. The third direction crosses a plane (the Z-X plane) including the first and second directions. The third direction is, for example, the Y-axis direction. 
     As shown in  FIGS. 11B and 12B , the first connection member CN 1  electrically connects the second counter magnetic layer  12   o  of one of the multiple first extension parts  11   x  and the second counter magnetic layer  12   o  of another one of the multiple first extension parts  11   x.    
     For example, the first counter magnetic layer  11   o  of the other one of the multiple first extension parts  11   x  is the one end  11 Ee of the first magnetic element  11 E. The first counter magnetic layer  11   o  of the one of the multiple first extension parts  11   x  is the other end  11 Ef of the first magnetic element  11 E. 
     As shown in  FIG. 11B , for example, the element current circuit  75  supplies the element current Id to a current path between the one end  11 Ee of the first magnetic element  11 E and the other end  11 Ef of the first magnetic element  11 E. A value that corresponds to the electrical resistance of the first magnetic element  11 E can be detected using the change of the element current Id. 
       FIGS. 13A and 13B  are schematic views illustrating a magnetic sensor according to the second embodiment. 
       FIG. 13A  is a line A 1 -A 2  cross-sectional view of  FIG. 13B .  FIG. 13B  is a plan view. 
       FIGS. 14A and 14B  are schematic cross-sectional views illustrating the magnetic sensor according to the second embodiment. 
     In the magnetic sensor  115  according to the embodiment as shown in  FIGS. 13A and 13B , the first sensor part  10 A further includes the first conductive member  21  in addition to the first magnetic member  51 , the first counter magnetic member  51 A, the first magnetic element  11 E, and the other first counter magnetic member  51 B. Otherwise, the configuration of the magnetic sensor  115  may be similar to the configuration of the magnetic sensor  114 . 
     In the magnetic sensor  115 , in the second direction (the Z-axis direction), the first conductive member  21  overlaps the region  66   a  between the first magnetic member  51  and the first counter magnetic member  51 A and a region  66   a  A between the first counter magnetic member  51 A and the other first counter magnetic member  51 B. 
     The first current circuit  71  is electrically connected with the one end  21   e  of the first conductive member  21  and the other end  21   f  of the first conductive member  21 . The first current that includes an alternating current component is supplied from the first current circuit  71  to the first conductive member  21 . 
     Third Embodiment 
       FIG. 15 ,  FIG. 16 , and  FIGS. 17A to 17C  are schematic views illustrating a magnetic sensor according to a third embodiment. 
       FIGS. 15 and 16  are plan views,  FIGS. 17A to 17C  are cross-sectional views. 
     As shown in  FIG. 15 , the magnetic sensor  120  according to the embodiment further includes a second sensor part  10 B that includes a second magnetic element  12 E, a third sensor part  10 C that includes a third magnetic element  13 E, a fourth sensor part  10 D that includes a fourth magnetic element  14 E, and the element current circuit  75  in addition to the first sensor part  10 A that includes the first magnetic element  11 E. 
     The second to fourth magnetic elements  12 E to  14 E each may have the configuration of the first magnetic element  11 E. In the example, these magnetic elements have the configuration of the first magnetic element  11 E of the magnetic sensor  113 . 
     In the example, the one end  11 Ee of the first magnetic element  11 E is electrically connected with one end  13 Ee of the third magnetic element  13 E. The other end  11 Ef of the first magnetic element  11 E is electrically connected with one end  12 Ee of the second magnetic element  12 E. Another end  13 Ef of the third magnetic element  13 E is electrically connected with one end  14 Ee of the fourth magnetic element  14 E. Another end  12 Ef of the second magnetic element  12 E is electrically connected with another end  14 Ef of the fourth magnetic element  14 E. 
     As shown in  FIG. 15 , the element current circuit  75  is configured to supply the element current Id between a first connection point CP 1  and a second connection point CP 2 , in which the first connection point CP 1  is between the one end  11 Ee of the first magnetic element  11 E and the one end  13 Ee of the third magnetic element  13 E, and the second connection point CP 2  is between the other end  12 Ef of the second magnetic element  12 E and the other end  14 Ef of the fourth magnetic element  14 E. 
     As shown in  FIG. 15 , the magnetic sensor  120  may further include a detection circuit  73 . The detection circuit  73  is configured to detect the change of the potential between a third connection point CP 3  and a fourth connection point CP 4 , in which the third connection point CP 3  is between the other end  11 Ef of the first magnetic element  11 E and the one end  12 Ee of the second magnetic element  12 E, and the fourth connection point CP 4  is between the other end  13 Ef of the third magnetic element  13 E and the one end  14 Ee of the fourth magnetic element  14 E. 
     The first to fourth magnetic elements  11 E to  14 E have a bridge connection. The change of the potential between two midpoints (the third connection point CP 3  and the fourth connection point CP 4 ) of the bridge circuit is detected by the detection circuit  73 . The detection has higher sensitivity due to the bridge circuit. 
     As described above with reference to  FIG. 7A , the first sensor part  10 A includes the first conductive member  21 . As shown in  FIG. 7A , in the second direction (the Z-axis direction), at least a portion of the first conductive member  21  overlaps the region  66   a  between the first magnetic member  51  and the first counter magnetic member  51 A. 
     As shown in  FIG. 17A , the second sensor part  10 B includes a second magnetic member  52 , a second counter magnetic member  52 A, and a second conductive member  22 . In the second direction (the Z-axis direction), at least a portion of the second conductive member  22  overlaps a region  66   b  between the second magnetic member  52  and the second counter magnetic member  52 A. The region  66   b  may be a portion of a second insulating member  65   b.    
     As shown in  FIG. 17B , the third sensor part  10 C includes a third magnetic member  53 , a third counter magnetic member  53 A, and a third conductive member  23 . In the second direction (the Z-axis direction), at least a portion of the third conductive member  23  overlaps a region  66   c  between the third magnetic member  53  and the third counter magnetic member  53 A. The region  66   c  may be a portion of a third insulating member  65   c.    
     As shown in  FIG. 17C , the fourth sensor part  10 D includes a fourth magnetic member  54 , a fourth counter magnetic member  54 A, and a fourth conductive member  24 . In the second direction (the Z-axis direction), at least a portion of the fourth conductive member  24  overlaps a region  66   d  between the fourth magnetic member  54  and the fourth counter magnetic member  54 A. The region  66   d  may be a portion of a fourth insulating member  65   d.    
     As shown in  FIG. 16 , the one end  21   e  of the first conductive member  21  is electrically connected with one end  23   e  of the third conductive member  23 . The other end  21   f  of the first conductive member  21  is electrically connected with one end  22   e  of the second conductive member  22 . Another end  23   f  of the third conductive member  23  is electrically connected with one end  24   e  of the fourth conductive member  24 . Another end  22   f  of the second conductive member  22  is electrically connected with another end  24   f  of the fourth conductive member  24 . 
     As shown in  FIG. 16 , the first current circuit  71  is configured to supply the first current I 1  that includes an alternating current component between a fifth connection point CP 5  and a sixth connection point CP 6 , in which the fifth connection point CP 5  is between the other end  21   f  of the first conductive member  21  and the one end  22   e  of the second conductive member  22 , and the sixth connection point CP 6  is between the other end  23   f  of the third conductive member  23  and the one end  24   e  of the fourth conductive member  24 . Noise components are further suppressed by using the first current I 1  that includes the alternating current component. Higher sensitivity is obtained. 
     According to the second embodiment, the relationship (the phase) between the orientation of the current flowing in the first magnetic element  11 E and the orientation of the current flowing in the first conductive member  21  of the first sensor part  10 A is opposite to the relationship (the phase) between the orientation of the current flowing in the third magnetic element  13 E and the orientation of the current flowing in the third conductive member  23  of the third sensor part  10 C. The relationship (the phase) between the orientation of the current flowing in the second magnetic element  12 E and the orientation of the current flowing in the second conductive member  22  of the second sensor part  10 B is opposite to the relationship (the phase) between the orientation of the current flowing in the fourth magnetic element  14 E and the orientation of the current flowing in the fourth conductive member  24  of the fourth sensor part  10 D. The relationship (the phase) between the orientation of the current flowing in the first magnetic element  11 E and the orientation of the current flowing in the first conductive member  21  of the first sensor part  10 A is opposite to the relationship (the phase) between the orientation of the current flowing in the second magnetic element  12 E and the orientation of the current flowing in the second conductive member  22  of the second sensor part  10 B. 
     For example, as shown in  FIG. 17A , the direction from the second magnetic member  52  toward the second counter magnetic member  52 A is along the first direction (the X-axis direction). The second magnetic element  12 E includes one or multiple second extension parts  12   x  (referring to  FIG. 15 ). As shown in  FIG. 17A , the second extension part  12   x  includes a second magnetic layer  12 , the second counter magnetic layer  12   o,  and the second nonmagnetic layer  12   n.  The second magnetic layer  12  includes a second portion p 2 , the second counter portion pA 2 , and the second middle portion pM 2 . The direction from the second portion p 2  toward the second counter portion pA 2  is along the second direction (the Z-axis direction). The second middle portion pM 2  is between the second portion p 2  and the second counter portion pA 2 . The second nonmagnetic layer  12   n  is between the second counter magnetic layer  12   o  and at least a portion of the second middle portion pM 2  in the second direction. 
     For example, as shown in  FIG. 17B , the direction from the third magnetic member  53  toward the third counter magnetic member  53 A is along the first direction (the X-axis direction). The third magnetic element  13 E includes due to one or multiple third extension parts  13   x  (referring to  FIG. 15 ). As shown in  FIG. 17B , the third extension part  13   x  includes a third magnetic layer  13 , a third counter magnetic layer  13   o,  and a third nonmagnetic layer  13   n.  The third magnetic layer  13  includes a third portion p 3 , a third counter portion pA 3 , and a third middle portion pM 3 . The direction from the third portion p 3  toward the third counter portion pA 3  is along the second direction (the Z-axis direction). The third middle portion pM 3  is between the third portion p 3  and the third counter portion pA 3 . The third nonmagnetic layer  13   n  is between the third counter magnetic layer  13   o  and at least a portion of the third middle portion pM 3  in the second direction. 
     For example, as shown in  FIG. 17C , the direction from the fourth magnetic member  54  toward the fourth counter magnetic member  54 A is along the first direction (the X-axis direction). The fourth magnetic element  14 E includes one or multiple fourth extension parts  14   x  (referring to  FIG. 15 ). As shown in  FIG. 17C , the fourth extension part  14   x  includes a fourth magnetic layer  14 , a fourth counter magnetic layer  140 , and a fourth nonmagnetic layer  14   n.  The fourth magnetic layer  14  includes a fourth portion p 4 , a fourth counter portion pA 4 , and a fourth middle portion pM 4 . The direction from the fourth portion p 4  toward the fourth counter portion pA 4  is along the second direction (the Z-axis direction). The fourth middle portion pM 4  is between the fourth portion p 4  and the fourth counter portion pA 4 . The fourth nonmagnetic layer  14   n  is between the fourth counter magnetic layer  140  and at least a portion of the fourth middle portion pM 4  in the second direction. 
     Fourth Embodiment 
     A fourth embodiment relates to an inspection device. As described below, the inspection device may include a diagnostic device. 
       FIG. 18  is a schematic view illustrating the inspection device according to the fourth embodiment. 
     As shown in  FIG. 18 , the inspection device  550  according to the embodiment includes a processor  78  and the magnetic sensor (in the example of  FIG. 18 , the magnetic sensor  110 ) according to the embodiment. The processor  78  processes an output signal SigX obtained from the magnetic sensor  110 . In the example, the processor  78  includes a sensor control circuit part  75   c,  a first lock-in amplifier  75   a,  and a second lock-in amplifier  75   b.  For example, the first current circuit  71  is controlled by the sensor control circuit part  75   c;  and the first current  11  that includes the alternating current component is supplied from the first current circuit  71  to a sensor part  10 S. The frequency of the alternating current component of the first current I 1  is, for example, not more than 100 kHz. The element current Id is supplied from the element current circuit  75  to the sensor part  10 S. The sensor part  10 S includes, for example, the first sensor part  10 A, etc. The sensor part  10 S may include the first to fourth sensor parts  10 A to  10 D, etc. The change of the potential of the sensor part  10 S is detected by the detection circuit  73 . For example, the output of the detection circuit  73  is the output signal SigX. 
     In the example, the inspection device  550  includes a magnetic field application part  76 A. The magnetic field application part  76 A is configured to apply a magnetic field to a detection object  80 . The detection object  80  is, for example, the inspection object. The detection object  80  includes at least an inspection conductive member  80   c  such as a metal, etc. For example, an eddy current is generated in the inspection conductive member  80   c  when the magnetic field due to the magnetic field application part  76 A is applied to the inspection conductive member  80   c.  The state of the eddy current changes when there is a flaw or the like in the inspection conductive member  80   c.  The state (e.g., the flaw, etc.) of the inspection conductive member  80   c  can be inspected by the magnetic sensor (e.g., the magnetic sensor  110 , etc.) detecting the magnetic field due to the eddy current. The magnetic field application part  76 A is, for example, an eddy current generator. 
     In the example, the magnetic field application part  76 A includes an application control circuit part  76   a,  a drive amplifier  76   b,  and a coil  76   c.  A current is supplied to the drive amplifier  76   b  by the control by the application control circuit part  76   a.  The current is, for example, an alternating current. The frequency of the current is, for example, an eddy current excitation frequency. The eddy current excitation frequency is, for example, not less than 10 Hz and not more than 100 kHz. The eddy current excitation frequency may be, for example, less than 100 kHz. 
     For example, information (which may be, for example, a signal) that relates to the frequency of the alternating current component of the first current I 1  is supplied from the sensor control circuit part  75   c  to the first lock-in amplifier  75   a  as a reference wave (a reference signal). The output of the first lock-in amplifier  75   a  is supplied to the second lock-in amplifier  75   b.  Information (which may be, for example, a signal) that relates to the eddy current excitation frequency is supplied from the application control circuit part  76   a  to the second lock-in amplifier  75   b  as a reference wave (a reference signal). The second lock-in amplifier  75   b  is configured to output a signal component corresponding to the eddy current excitation frequency. 
     Thus, for example, the processor  78  includes the first lock-in amplifier  75   a.  The output signal SigX that is obtained from the magnetic sensor  110  and a signal SigR 1  that corresponds to the frequency of the alternating current component included in the first current I 1  are input to the first lock-in amplifier  75   a.  The first lock-in amplifier  75   a  is configured to output an output signal SigX 1  that uses the signal SigR 1  corresponding to the frequency of the alternating current component included in the first current I 1  as a reference wave (a reference signal). By providing the first lock-in amplifier  75   a,  it is possible to suppress noise and detect with high sensitivity. 
     The processor  78  may further include the second lock-in amplifier  75   b.  The output signal SigX 1  of the first lock-in amplifier  75   a  and a signal SigR 2  that corresponds to the frequency (the eddy current excitation frequency) of the supply signal (in the example, the magnetic field due to the magnetic field application part  76 A) supplied toward the detection object  80  (the inspection object) are input to the second lock-in amplifier  75   b.  The second lock-in amplifier  75   b  is configured to output an output signal SigX 2  that uses the signal SigR 2  corresponding to the frequency of the supply signal supplied toward the detection object  80  (the inspection object) as a reference wave (a reference signal). By providing the second lock-in amplifier  75   b,  it is possible to further suppress noise and detect with even higher sensitivity. 
     An abnormality such as a flaw or the like of the inspection conductive member  80   c  of the detection object  80  can be inspected by the inspection device  550 . 
       FIG. 19  is a schematic view illustrating an inspection device according to the third embodiment. 
     As shown in  FIG. 19 , the inspection device  551  according to the embodiment includes the processor  78  and the magnetic sensor (e.g., the magnetic sensor  110 ) according to the embodiment. The configurations of the magnetic sensor and the processor  78  of the inspection device  551  may be similar to those of the inspection device  550 . In the example, the inspection device  551  includes a detection object driver  76 B. The detection object driver  76 B is configured to supply a current to the inspection conductive member  80   c  included in the detection object  80 . The inspection conductive member  80   c  is, for example, wiring included in the detection object  80 . A magnetic field that is due to a current  80 i flowing in the inspection conductive member  80   c  is detected by the magnetic sensor  110 . The inspection conductive member  80   c  can be inspected based on an abnormality due to the detection result of the magnetic sensor  110 . The detection object  80  may be, for example, an electronic device such as a semiconductor device, etc. The detection object  80  may be, for example, a battery, etc. 
     In the example, the detection object driver  76 B includes the application control circuit part  76   a  and the drive amplifier  76   b.  The drive amplifier  76   b  is controlled by the application control circuit part  76   a;  and a current is supplied from the drive amplifier  76   b  to the inspection conductive member  80   c.  The current is, for example, an alternating current. For example, the alternating current is supplied to the inspection conductive member  80   c.  The frequency of the alternating current is, for example, not less than 10 Hz and not more than 100 kHz. The frequency may be, for example, less than 100 kHz. In the example as well, for example, by providing the first lock-in amplifier  75   a  and the second lock-in amplifier  75   b,  it is possible to suppress noise and detect with high sensitivity. In one example of the inspection device  551 , multiple magnetic sensors (e.g., the multiple magnetic sensors  110 ) may be provided. The multiple magnetic sensors are, for example, a sensor array. The inspection conductive member  80   c  can be inspected in a short period of time by the sensor array. In one example of the inspection device  551 , the inspection conductive member  80   c  may be inspected by scanning the magnetic sensor (e.g., the magnetic sensor  110 ). 
       FIG. 20  is a schematic perspective view showing an inspection device according to the fourth embodiment. 
     As shown in  FIG. 20 , the inspection device  710  according to the embodiment includes a magnetic sensor  150   a  and a processor  770 . The magnetic sensor  150   a  may be the magnetic sensor according to one of the first to third embodiments or a modification of the magnetic sensor. The processor  770  processes an output signal obtained from the magnetic sensor  150   a.  The processor  770  may perform a comparison between a reference value and the signal obtained from the magnetic sensor  150   a,  etc. The processor  770  is configured to output an inspection result based on the processing result. 
     For example, an inspection object  680  is inspected by the inspection device  710 . The inspection object  680  is, for example, an electronic device (including a semiconductor circuit, etc.). The inspection object  680  may be, for example, a battery  610 , etc. 
     For example, the magnetic sensor  150   a  according to the embodiment may be used together with the battery  610 . For example, a battery system  600  includes the battery  610  and the magnetic sensor  150   a.  The magnetic sensor  150   a  can detect a magnetic field generated by a current flowing in the battery  610 . 
       FIG. 21  is a schematic plan view showing the inspection device according to the fourth embodiment. 
     As shown in  FIG. 21 , the magnetic sensor  150   a  includes, for example, multiple magnetic sensors according to the embodiment. In the example, the magnetic sensor  150   a  includes multiple magnetic sensors (e.g., the magnetic sensor  110 , etc.). For example, the multiple magnetic sensors are arranged along two directions (e.g., the X-axis direction and the Y-axis direction). For example, the multiple magnetic sensors  110  are located on a substrate. 
     The magnetic sensor  150   a  can detect a magnetic field generated by a current flowing in the inspection object  680  (which may be, for example, the battery  610 ). For example, an abnormal current flows in the battery  610  when the battery  610  approaches an abnormal state. The change of the state of the battery  610  can be known by the magnetic sensor  150   a  detecting the abnormal current. For example, the entire battery  610  can be inspected in a short period of time by moving the sensor array in two directions while the magnetic sensor  150   a  is proximate to the battery  610 . The magnetic sensor  150   a  may be used to inspect the battery  610  in the manufacturing process of the battery  610 . 
     For example, the magnetic sensor according to the embodiment is applicable to the inspection device  710  such as a diagnostic device, etc.  FIG. 22  is a schematic view showing the magnetic sensor and the inspection device according to the fourth embodiment. 
     As shown in  FIG. 22 , the diagnostic device  500  is an example of the inspection device  710  and includes the magnetic sensor  150 . The magnetic sensor  150  includes the magnetic sensors described in reference to the first to fifth embodiments and modifications of the magnetic sensors. 
     In the diagnostic device  500 , the magnetic sensor  150  is, for example, a magnetoencephalography device. The magnetoencephalography device detects a magnetic field generated by cranial nerves. When the magnetic sensor  150  is included in a magnetoencephalography device, the size of the magnetic element included in the magnetic sensor  150  is, for example, not less than 1 mm but less than 10 mm. The size is, for example, the length including the MFC. 
     As shown in  FIG. 22 , the magnetic sensor  150  (the magnetoencephalography device) is mounted to, for example, the head of a human body. The magnetic sensor  150  (the magnetoencephalography device) includes a sensor part  301 . The magnetic sensor  150  (the magnetoencephalography device) may include multiple sensor parts  301 . The number of the multiple sensor parts  301  is, for example, about 100 (e.g., not less than 50 and not more than 150). The multiple sensor parts  301  are provided on a flexible base body  302 . 
     The magnetic sensor  150  may include, for example, a circuit for differential detection, etc. The magnetic sensor  150  may include a sensor other than a magnetic sensor (e.g., a potential terminal, an acceleration sensor, etc.). 
     The size of the magnetic sensor  150  is small compared to the size of a conventional SQUID magnetic sensor. Therefore, the mounting of the multiple sensor parts  301  is easy. The mounting of the multiple sensor parts  301  and the other circuits is easy. The multiple sensor parts  301  and the other sensors can be easily mounted together. 
     The base body  302  may include, for example, an elastic body such as a silicone resin, etc. For example, the multiple sensor parts  301  are linked to each other and provided in the base body  302 . For example, the base body  302  can be closely adhered to the head. 
     An input/output cord  303  of the sensor part  301  is connected with a sensor driver  506  and a signal input/output part  504  of the diagnostic device  500 . A magnetic field measurement is performed in the sensor part  301  based on electrical power from the sensor driver  506  and a control signal from the signal input/output part  504 . The result is input to the signal input/output part  504 . The signal that is obtained by the signal input/output part  504  is supplied to a signal processor  508 . Processing such as, for example, the removal of noise, filtering, amplification, signal calculation, etc., are performed in the signal processor  508 . The signal that is processed by the signal processor  508  is supplied to a signal analyzer  510 . For example, the signal analyzer  510  extracts a designated signal for magnetoencephalography. For example, signal analysis to match the signal phases is performed in the signal analyzer  510 . 
     The output of the signal analyzer  510  (the data for which the signal analysis is finished) is supplied to a data processor  512 . Data analysis is performed in the data processor  512 . It is possible to include image data such as, for example, MRI (Magnetic Resonance Imaging), etc., in the data analysis. It is possible to include, for example, scalp potential information such as EEG (Electroencephalogram), etc., in the data analysis. For example, a data part  514  of the MRI, the EEG, etc., is connected with the data processor  512 . For example, nerve firing point analysis, inverse analysis, or the like is performed by the data analysis. 
     For example, the result of the data analysis is supplied to an imaging diagnostic part  516 . Imaging is performed by the imaging diagnostic part  516 . The diagnosis is supported by the imaging. 
     For example, the series of operations described above is controlled by a control mechanism  502 . For example, necessary data such as preliminary signal data, metadata partway through the data processing, or the like is stored in a data server. The data server and the control mechanism may be integrated. 
     The diagnostic device  500  according to the embodiment includes the magnetic sensor  150 , and a processor that processes the output signal obtained from the magnetic sensor  150 . The processor includes, for example, at least one of the signal processor  508  or the data processor  512 . The processor includes, for example, a computer, etc. 
     In the magnetic sensor  150  shown in  FIG. 22 , the sensor part  301  is mounted to the head of a human body. The sensor part  301  may be mounted to the chest of the human body. Magnetocardiography is possible thereby. For example, the sensor part  301  may be mounted to the abdomen of a pregnant woman. Palmoscopy of the fetus can be performed thereby. 
     It is favorable for the magnetic sensor device including the participant to be mounted inside a shielded room. For example, the effects of geomagnetism or magnetic noise can be suppressed thereby. 
     For example, a mechanism may be provided to locally shield the sensor part  301  or the measurement section of the human body. For example, a shield mechanism may be provided in the sensor part  301 . For example, the signal analysis or the data processing may be effectively shielded. 
     According to the embodiment, the base body  302  may be flexible or may be substantially not flexible. In the example shown in  FIG. 22 , the base body  302  is a continuous membrane that is patterned into a hat-like configuration. The base body  302  may have a net configuration. For example, a good fit is obtained thereby. For example, the adhesion of the base body  302  to the human body is improved. The base body  302  may have a hard helmet-like configuration. 
       FIG. 23  is a schematic view showing the inspection device according to the fourth embodiment. 
       FIG. 23  is an example of a magnetic detection instrument. In the example, the sensor part  301  is provided on a hard base body  305  having a flat plate shape. 
     The input and output of the signal obtained from the sensor part  301  in the example shown in  FIG. 23  are similar to the input and output described with reference to  FIG. 22 . The processing of the signal obtained from the sensor part  301  in the example shown in  FIG. 23  is similar to the processing described with reference to  FIG. 22 . 
     There is a reference example in which a SQUID (Superconducting Quantum Interference Device) magnetic sensor is used as a device to measure a faint magnetic field such as a magnetic field emitted from a living body, etc. Because superconductivity is used in the reference example, the device is large; and the power consumption is large. The load on the measurement object (the patient) is large. 
     According to the embodiment, the device can be small. The power consumption can be suppressed. The load on the measurement object (the patient) can be reduced. According to the embodiment, the SN ratio of the magnetic field detection can be improved. The sensitivity can be increased. 
     Embodiments may include the following configurations (e.g., technological proposals). 
     Configuration 1 
     A magnetic sensor, comprising: 
     a first sensor part including
         a first magnetic member,   a first counter magnetic member, a direction from the first magnetic member toward the first counter magnetic member being along a first direction, and   a first magnetic element including one or a plurality of first extension parts,       

     the first extension part including a first magnetic layer, a first counter magnetic layer, and a first nonmagnetic layer, 
     the first magnetic layer including a first portion, a first counter portion, and a first middle portion, 
     a direction from the first portion toward the first counter portion being along the first direction, 
     the first middle portion being between the first portion and the first counter portion, 
     the first nonmagnetic layer being between the first counter magnetic layer and at least a portion of the first middle portion in a second direction crossing the first direction. 
     Configuration 2 
     The magnetic sensor according to Configuration 1, wherein 
     a position in the first direction of the first nonmagnetic layer is between a position in the first direction of the first magnetic member and a position in the first direction of the first counter magnetic member. 
     Configuration 3 
     The magnetic sensor according to Configuration 1 or 2, wherein 
     the first sensor part further includes a first insulating member, and 
     at least a portion of the first insulating member is between the first portion and the first magnetic member and between the first counter portion and the first counter magnetic member. 
     Configuration 4 
     The magnetic sensor according to any one of Configurations 1 to 3, wherein 
     a first magnetic layer length along the first direction of the first magnetic layer is not less than 2 times a first distance, and 
     the first distance is along the first direction between the first magnetic member and the first counter magnetic member. 
     Configuration 5 
     The magnetic sensor according to Configuration 4, wherein 
     a first nonmagnetic layer length along the first direction of the first nonmagnetic layer is not more than the first distance. 
     Configuration 6 
     The magnetic sensor according to any one of Configurations 1 to 5, wherein 
     the first extension part further includes a first layer, 
     the first layer includes at least one selected from the group consisting of IrMn and PtMn, 
     the first counter magnetic layer is located between the first magnetic layer and the first layer, and 
     the first nonmagnetic layer includes MgO. 
     Configuration 7 
     The magnetic sensor according to any one of Configurations 1 to 6, wherein 
     the first sensor part includes a first conductive member, 
     in the second direction, at least a portion of the first conductive member overlaps a region between the first magnetic member and the first counter magnetic member, 
     a first current includes an alternating current component and can flow in the first conductive member, 
     the first current flows through the first conductive member along a third direction, and 
     the third direction crosses a plane including the first and second directions. 
     Configuration 8 
     The magnetic sensor according to any one of Configurations 1 to 7, wherein 
     an electrical resistance of the first magnetic element has an even-function characteristic with respect to a magnetic field applied to the first magnetic element. 
     Configuration 9 
     The magnetic sensor according to any one of Configurations 1 to 8, wherein 
     an electrical resistance of the first magnetic element has a first value when a first magnetic field is applied to the first magnetic element, 
     the electrical resistance has a second value when a second magnetic field is applied to the first magnetic element, 
     the electrical resistance has a third value when a third magnetic field is applied to the first magnetic element, 
     an absolute value of the first magnetic field is less than an absolute value of the second magnetic field and less than an absolute value of the third magnetic field, 
     an orientation of the second magnetic field is opposite to an orientation of the third magnetic field, and 
     the first value is less than the second value and less than the third value. 
     Configuration 10 
     The magnetic sensor according to any one of Configurations 1 to 9, wherein 
     the first extension part includes a second counter magnetic layer and a second nonmagnetic layer, 
     the first nonmagnetic layer is between the first counter magnetic layer and a portion of the first middle portion in the second direction, 
     the second nonmagnetic layer is between the second counter magnetic layer and an other portion of the first middle portion in the second direction, and 
     a direction from the second nonmagnetic layer toward the first nonmagnetic layer is along a third direction crossing a plane including the first and second directions. 
     Configuration 11 
     The magnetic sensor according to Configuration 10, wherein 
     the first magnetic element includes the plurality of first extension parts, and 
     the plurality of first extension parts is arranged along a third direction crossing a plane including the first and second directions. 
     Configuration 12 
     The magnetic sensor according to Configuration 11, wherein a direction from the first nonmagnetic layer of one of the plurality of first extension parts toward the first nonmagnetic layer of an other one of the plurality of first extension parts is along the third direction. 
     Configuration 13 
     The magnetic sensor according to Configuration 11 or 12, wherein 
     the first magnetic element further includes a first connection member, and 
     the first connection member electrically connects the second counter magnetic layer of one of the plurality of first extension parts and the first counter magnetic layer of an other one of the plurality of first extension parts. 
     Configuration 14 
     The magnetic sensor according to any one of Configurations 1 to 13, wherein 
     the first sensor part further includes an other first counter magnetic member, 
     the first counter magnetic member is between the first magnetic member and the other first counter magnetic member in the first direction, 
     the first extension part further includes a second counter magnetic layer and a second nonmagnetic layer, 
     the first magnetic layer further includes a second counter portion and a second middle portion, 
     the first counter portion is between the first portion and the second counter portion in the first direction, 
     the second middle portion is between the first counter portion and the second counter portion, and the second nonmagnetic layer is between the second counter magnetic layer and at least a portion of the second middle portion in the second direction. 
     Configuration 15 
     The magnetic sensor according to Configuration 14, wherein 
     the first magnetic element includes the plurality of first extension parts and a first connection member, 
     the plurality of first extension parts is arranged along a third direction crossing a plane including the first and second directions, and 
     the first connection member electrically connects the second counter magnetic layer of one of the plurality of first extension parts and the second counter magnetic layer of an other one of the plurality of first extension parts. 
     Configuration 16 
     The magnetic sensor according to any one of Configurations 1 to 9, further comprising: 
     a second sensor part including a second magnetic element, 
     a third sensor part including a third magnetic element, 
     a fourth sensor part including a fourth magnetic element, and 
     an element current circuit, 
     one end of the first magnetic element being electrically connected with one end of the third magnetic element, 
     an other end of the first magnetic element being electrically connected with one end of the second magnetic element, 
     an other end of the third magnetic element being electrically connected with one end of the fourth magnetic element, 
     an other end of the second magnetic element being electrically connected with an other end of the fourth magnetic element, 
     the element current circuit being configured to supply an element current between a first connection point and a second connection point, 
     the first connection point being between the one end of the first magnetic element and the one end of the third magnetic element, 
     the second connection point being between the other end of the second magnetic element and the other end of the fourth magnetic element. 
     Configuration 17 
     The magnetic sensor according to Configuration 16, further comprising: 
     a detection circuit, 
     the detection circuit being configured to detect a change of a potential between a third connection point and a fourth connection point, 
     the third connection point being between the other end of the first magnetic element and the one end of the second magnetic element, 
     the fourth connection point being between the other end of the third magnetic element and the one end of the fourth magnetic element. 
     Configuration 18 
     The magnetic sensor according to Configuration 16 or 17, further comprising: 
     a first current circuit, 
     the first sensor part including a first conductive member, 
     in the second direction, at least a portion of the first conductive member overlapping a region between the first magnetic member and the first counter magnetic member, 
     the second sensor part including a second magnetic member, a second counter magnetic member, and a second conductive member, 
     in the second direction, at least a portion of the second conductive member overlapping a region between the second magnetic member and the second counter magnetic member, 
     the third sensor part including a third magnetic member, a third counter magnetic member, and a third conductive member, 
     in the second direction, at least a portion of the third conductive member overlapping a region between the third magnetic member and the third counter magnetic member, 
     the fourth sensor part including a fourth magnetic member, a fourth counter magnetic member, and a fourth conductive member, 
     in the second direction, at least a portion of the fourth conductive member overlapping a region between the fourth magnetic member and the fourth counter magnetic member, 
     one end of the first conductive member being electrically connected with one end of the third conductive member, 
     an other end of the first conductive member being electrically connected with one end of the second conductive member, 
     an other end of the third conductive member being electrically connected with one end of the fourth conductive member, 
     an other end of the second conductive member being electrically connected with an other end of the fourth conductive member, 
     the first current circuit being configured to supply a first current between a fifth connection point and a sixth connection point, 
     the first current including an alternating current component, 
     the fifth connection point being between the other end of the first conductive member and the one end of the second conductive member, 
     the sixth connection point being between the other end of the third conductive member and the one end of the fourth conductive member. 
     Configuration 19 
     The magnetic sensor according to any one of Configurations 16 to 18, wherein 
     the second sensor part includes:
         a second magnetic member; and   a second counter magnetic member,       

     a direction from the second magnetic member toward the second counter magnetic member is along the first direction, 
     the second magnetic element includes one or a plurality of second extension parts, 
     the second extension part includes a second magnetic layer, a second counter magnetic layer, and a second nonmagnetic layer, 
     the second magnetic layer includes a second portion, a second counter portion, and a second middle portion, 
     a direction from the second portion toward the second counter portion is along the second direction, 
     the second middle portion is between the second portion and the second counter portion, 
     the second nonmagnetic layer is between the second counter magnetic layer and at least a portion of the second middle portion in the second direction, 
     the third sensor part includes:
         a third magnetic member; and   a third counter magnetic member,       

     a direction from the third magnetic member toward the third counter magnetic member is along the first direction, 
     the third magnetic element includes one or a plurality of third extension parts, 
     the third extension part includes a third magnetic layer, a third counter magnetic layer, and a third nonmagnetic layer, 
     the third magnetic layer includes a third portion, a third counter portion, and a third middle portion, 
     a direction from the third portion toward the third counter portion is along the second direction, 
     the third middle portion is between the third portion and the third counter portion, 
     the third nonmagnetic layer is between the third counter magnetic layer and at least a portion of the third middle portion in the second direction, 
     the fourth sensor part includes:
         a fourth magnetic member; and   a fourth counter magnetic member,       

     a direction from the fourth magnetic member toward the fourth counter magnetic member is along the first direction, 
     the fourth magnetic element includes one or a plurality of fourth extension parts, 
     the fourth extension part includes a fourth magnetic layer, a fourth counter magnetic layer, and a fourth nonmagnetic layer, 
     the fourth magnetic layer includes a fourth portion, a fourth counter portion, and a fourth middle portion, 
     a direction from the fourth portion toward the fourth counter portion is along the second direction, 
     the fourth middle portion is between the fourth portion and the fourth counter portion, 
     the fourth nonmagnetic layer is between the fourth counter magnetic layer and at least a portion of the fourth middle portion in the second direction. 
     Configuration 20 
     An inspection device, comprising: 
     the magnetic sensor according to any one of Configurations 1 to 19; and 
     a processor configured to process a signal output from the magnetic sensor. 
     According to embodiments, a magnetic sensor and an inspection device can be provided in which the sensitivity can be increased. 
     In the specification of the application, “perpendicular” and “parallel” refer to not only strictly perpendicular and strictly parallel but &amp;so include, for example, the fluctuation due to manufacturing processes, etc. It is sufficient to be substantially perpendicular and substantially parallel. 
     Hereinabove, exemplary embodiments of the invention are described with reference to specific examples. However, the embodiments of the invention are not limited to these specific examples. For example, one skilled in the art may similarly practice the invention by appropriately selecting specific configurations of components included in magnetic sensors such as sensor parts, magnetic elements, magnetic layers, nonmagnetic layers, magnetic members, circuits, etc., from known art. Such practice is included in the scope of the invention to the extent that similar effects thereto are obtained. 
     Further, any two or more components of the specific examples may be combined within the extent of technical feasibility and are included in the scope of the invention to the extent that the purport of the invention is included. 
     Moreover, all magnetic sensors, and inspection devices practicable by an appropriate design modification by one skilled in the art based on the magnetic sensors, and the inspection devices described above as embodiments of the invention also are within the scope of the invention to the extent that the purport of the invention is included. 
     Various other variations and modifications can be conceived by those skilled in the art within the spirit of the invention, and it is understood that such variations and modifications are also encompassed within the scope of the invention. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.