Magnetic sensor

Abstract

The technical problem to be solved by the present invention is to increase the magnetic bias applied to a magnetoresistive element by magnetically coupling a magnetoresistive strip with a ferromagnetic film in a magnetic sensor including the magnetoresistive strip and the ferromagnetic film. The solution is that a magnetic sensor (1) includes: a magnetoresistive strip (S); an insulating film (13) covering the magnetoresistive strip (S); and ferromagnetic films (M1, M2) which are provided on the insulating film (13) and are arranged in the x direction with a magnetic gap (G) extending in the y direction therebetween. The ferromagnetic films (M1, M2) overlap with a plurality of hard magnets (H) with the insulating film (13) therebetween. Thus, since two adjacent hard magnets (H) are magnetically coupled through the ferromagnetic films (M1, M2), the magnetic bias applied to the magnetoresistive element (R) can be increased without increasing the size of the hard magnets (H).

Description

Technical Field

[0001] The present invention relates to a magnetic sensor, and more particularly to a magnetic sensor for detecting a very weak magnetic field. Background Art

[0002] As a magnetic sensor, as described in Patent Document 1, a magnetic sensor of a type that detects the direction and intensity of a magnetic field based on a change in the resistance value of a magnetoresistive element is known. The magnetic sensor described in Patent Document 1 ensures a sufficient resistance value by bending the magnetoresistive element into a meandering shape, and applies a magnetic bias to the magnetoresistive element by arranging a plurality of hard magnetic bodies (magnets) that divide the magnetoresistive element. When applying a magnetic bias to the magnetoresistive element, it is preferable to make the magnetoresistive element single-domain, and thus irregular noise superimposed on the detection signal can be reduced.

[0003] In addition, in Figure 4 and Figure 5 of Patent Document 1, soft magnetic bodies are arranged on both sides of the magnetoresistive strip bent into a meandering shape, thereby shielding an unnecessary external magnetic field and improving the detection accuracy.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent No. 5066579 Summary of the Invention

[0007] [Technical Problem to be Solved by the Invention]

[0008] However, in the magnetic sensors described in Figure 4 and Figure 5 of Patent Document 1, the distance between the magnetoresistive strip and the soft magnetic body is relatively large, so the effect of the soft magnetic body cannot be fully obtained.

[0009] An object of the present invention is to provide a magnetic sensor including a magnetoresistive strip and a ferromagnetic film, which can improve the magnetic bias applied to the magnetoresistive element by magnetically coupling the magnetoresistive strip and the ferromagnetic film.

[0010] [Technical Means for Solving the Technical Problem]

[0011] The magnetic sensor of the present invention is characterized by including: a first magnetoresistive strip composed of a plurality of magnetoresistive elements arranged in a first direction with a plurality of hard magnetic bodies for applying a magnetic bias therebetween; an insulating film covering the first magnetoresistive strip; and a first ferromagnetic film and a second ferromagnetic film provided on the insulating film and arranged in a second direction intersecting the first direction with a first magnetic gap extending in the first direction therebetween; wherein at least one of the first ferromagnetic film and the second ferromagnetic film has a portion overlapping the plurality of hard magnetic bodies with the insulating film therebetween.

[0012] According to the present invention, since the ferromagnetic film has a portion overlapping with a plurality of hard magnetic bodies, two adjacent hard magnetic bodies are magnetically coupled via the ferromagnetic film. Thus, without increasing the size of the hard magnetic bodies, the magnetic bias applied to the magnetoresistive element can be increased.

[0013] The present invention may also be configured such that at least one of the first ferromagnetic film and the second ferromagnetic film has a portion overlapping with a plurality of magnetoresistive elements via an insulating film. By adopting such a structure, a detection magnetic field can be effectively applied to the plurality of magnetoresistive elements.

[0014] The present invention may also be configured such that both the first ferromagnetic film and the second ferromagnetic film have portions overlapping with a plurality of hard magnetic bodies and a plurality of magnetoresistive elements via an insulating film. By adopting such a structure, the magnetic bias can be further increased, and a detection magnetic field can be more effectively applied to the plurality of magnetoresistive elements.

[0015] The present invention may also be configured such that the portion of the first ferromagnetic film and the second ferromagnetic film overlapping with the plurality of magnetoresistive elements has a protruding portion whose bottom surface in contact with the insulating film protrudes toward the plurality of magnetoresistive elements, and the width of the protruding portion in the first direction is narrower than the width of each of the plurality of magnetoresistive elements in the first direction. By adopting such a structure, a detection magnetic field can be efficiently applied to the magnetoresistive element from the end portion, i.e., the corner portion, of the protruding portion, and thus higher sensitivity can be obtained.

[0016] The present invention may also be configured such that the thickness of the insulating film is 0.05 μm or more and 0.3 μm or less. By adopting such a structure, the insulation breakdown voltage between the ferromagnetic film and the magnetoresistive element can be ensured, and the magnetic bias can be sufficiently increased.

[0017] The magnetic sensor of the present invention may also be configured to further include: a second magnetoresistive strip composed of a plurality of magnetoresistive elements arranged in the first direction with a plurality of hard magnetic bodies for applying a magnetic bias therebetween; and a third ferromagnetic film provided on the insulating film; wherein the first ferromagnetic film and the third ferromagnetic film are arranged in the second direction with a second magnetic gap extending in the first direction therebetween, and at least one of the first ferromagnetic film and the third ferromagnetic film has a portion overlapping with a plurality of hard magnetic bodies included in the second magnetoresistive strip via an insulating film. By adopting such a structure, a half-bridge circuit can be formed by the first magnetoresistive strip and the second magnetoresistive strip.

[0018] The magnetic sensor of the present invention may also be configured to further include: a compensation coil for applying a canceling magnetic field to the first magnetoresistive strip and the second magnetoresistive strip, the compensation coil including: a first section extending in the first direction along the first magnetoresistive strip; and a second section extending in the first direction along the second magnetoresistive strip, and the directions of the currents flowing in the first section and the second section are opposite to each other. By adopting such a structure, closed-loop control can be performed on the first magnetoresistive strip and the second magnetoresistive strip.

[0019] The magnetic sensor of the present invention may also be configured to further include a third magnetoresistive band and a fourth magnetoresistive band, which are composed of a plurality of magnetoresistive elements arranged in the first direction via a plurality of hard magnetic bodies to which a magnetic bias is applied, the first ferromagnetic film and the second ferromagnetic film further form a third magnetic gap extending in the first direction, the first ferromagnetic film and the third ferromagnetic film further form a fourth magnetic gap extending in the first direction, at least one of the first ferromagnetic film and the second ferromagnetic film has a portion overlapping with the plurality of hard magnetic bodies included in the third magnetoresistive band via an insulating film, and at least one of the first ferromagnetic film and the third ferromagnetic film has a portion overlapping with the plurality of hard magnetic bodies included in the fourth magnetoresistive band via an insulating film. By adopting such a configuration, a full bridge circuit can be formed by the first to fourth magnetoresistive bands.

[0020] The magnetic sensor of the present invention may also be configured to further include a compensation coil for applying a canceling magnetic field to the first to fourth magnetoresistive bands, the compensation coil including: a first section extending in the first direction along the first magnetoresistive band; a second section extending in the first direction along the second magnetoresistive band; a third section extending in the first direction along the third magnetoresistive band; and a fourth section extending in the first direction along the fourth magnetoresistive band; wherein the directions of the currents flowing in the first section and the third section are the same, the directions of the currents flowing in the second section and the fourth section are the same, and the directions of the currents flowing in the first section and the second section are opposite to each other. By adopting such a structure, the first to fourth magnetoresistive bands can be closed-loop controlled.

[0021] The magnetic sensor of the present invention may also be configured to further include a first terminal electrode and a second terminal electrode, wherein one end of the first magnetoresistive band in the first direction is connected to the first terminal electrode without passing through another magnetoresistive element to which the detection magnetic field is applied, and the other end of the first magnetoresistive band in the first direction is connected to the second terminal electrode without passing through another magnetoresistive element to which the detection magnetic field is applied. By adopting such a structure, since the first magnetoresistive band is a straight line shape without a folding structure, the relationship between the direction of the magnetic bias and the direction of the current is fixed in the entire interval. As a result, irregular noise is greatly reduced, and very weak magnetic fields can be detected.

[0022] [Effects of the invention]

[0023] As described above, according to the present invention, since a closed magnetic circuit is formed by magnetic coupling between the magnetoresistive strip and the ferromagnetic film, the magnetic bias applied to the magnetoresistive element can be increased without increasing the size of the hard magnetic body. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic plan view for explaining the structure of the magnetic sensor 1 according to the first embodiment of the present invention.

[0025] Figure 2 (a) is alongFigure 1 Rough sectional view along line A-A shown Figure 2 (b) is along Figure 1 Rough sectional view along line B-B shown

[0026] Figure 3 is an enlarged view for explaining the positional relationship between the magnetoresistive tape S and the ferromagnetic film M1, corresponding to the cross-section along Figure 1 line A-A shown

[0027] Figure 4 (a) and (b) are schematic views for explaining the formation method of the insulating film 13 of the modification

[0028] Figure 5 is a graph showing the relationship between the film thickness of the insulating film 13 and the sensitivity of each magnetoresistive element R

[0029] Figure 6 is a graph showing the relationship between the film thickness of the insulating film 13 and the sensitivity of the magnetic sensor 1

[0030] Figure 7 is a graph showing the relationship between the film thickness of the insulating film 13 and the noise of the magnetic sensor 1

[0031] Figure 8 is a rough sectional view for explaining the structure of the magnetic sensor 2 of the second embodiment of the present invention

[0032] Figure 9 is a rough top view for explaining the structure of the magnetic sensor 2 of the second embodiment of the present invention

[0033] Figure 10 is a schematic view for explaining the connection relationship between the magnetoresistive tapes S1, S2 and the compensation coil C and the terminal electrodes E11~E13, E15, E16

[0034] Figure 11 is a rough top view for explaining the structure of the magnetic sensor 3 of the third embodiment of the present invention

[0035] Figure 12 is a schematic view for explaining the connection relationship between the magnetoresistive tapes S1~S4 and the compensation coil C and the terminal electrodes E11~E16 Detailed Embodiment

[0036] Hereinafter, with reference to the drawings, the preferred embodiments of the present invention will be described in detail

[0037] <First Embodiment>

[0038] Figure 1 is a rough top view for explaining the structure of the magnetic sensor 1 of the first embodiment of the present invention. In addition,Figure 2 (a) is a schematic cross-sectional view along Figure 1 the line A-A shown in Figure 2 (b) is a schematic cross-sectional view along Figure 1 the line B-B shown in

[0039] As shown in Figure 1 and Figure 2 , the magnetic sensor 1 of the first embodiment includes: a magnetoresistive strip S extending in the y direction; and two ferromagnetic films M1 and M2 arranged in the x direction. The magnetoresistive strip S is formed on the sensor substrate 11 with an insulating film 12 interposed therebetween, and is composed of a plurality of magnetoresistive elements R arranged in the y direction with a plurality of hard magnetic bodies (magnets) H interposed therebetween. As the material of the magnetoresistive element R, any material whose resistance value changes according to the direction and intensity of the magnetic field may be used, and there is no particular limitation. The magnetoresistive elements R are divided in the y direction by a plurality of hard magnetic bodies H, and are substantially formed into single magnetic domains due to the magnetic bias applied by the hard magnetic bodies H. Thereby, irregular noise generated due to the disorder of magnetic domains can be reduced. In order to reliably make the magnetoresistive elements R single magnetic domain, it is preferable to set the length of each magnetoresistive element R in the y direction to about several μm.

[0040] The magnetoresistive strip S is covered with an insulating film 13 composed of Al2O3 or the like. The ferromagnetic films M1 and M2 are formed on the surface of the insulating film 13 and are arranged in the x direction with a magnetic gap G extending in the y direction interposed therebetween. In the present embodiment, in a top view seen from the z direction, there is a portion where the magnetic gap G overlaps with the magnetoresistive strip S. More specifically, compared with the width of the magnetoresistive strip S in the x direction, the width of the magnetic gap G in the x direction is narrower. Therefore, in a top view seen from the z direction, the ferromagnetic films M1 and M2 have portions that partially overlap with the magnetoresistive elements R and the hard magnetic bodies H with the insulating film 13 interposed therebetween. Thereby, the detection magnetic field from the ferromagnetic film M1 toward the ferromagnetic film M2 or the detection magnetic field from the ferromagnetic film M2 toward the ferromagnetic film M1 is applied to the magnetoresistive strip S in the x direction.

[0041] And, as shown in Figure 2 (a), since two adjacent hard magnetic bodies H are magnetically coupled through the ferromagnetic films M1 and M2 to form a closed magnetic circuit, the magnetic bias φ applied to the magnetoresistive elements R can be enhanced as compared with the case where the hard magnetic bodies H and the ferromagnetic films M1 and M2 do not overlap. Thereby, the magnetic bias can be increased without increasing the size of the hard magnetic bodies H. In order to improve the magnetic coupling between the hard magnetic bodies H and the ferromagnetic films M1 and M2, it is sufficient to make the thickness of the insulating film 13 thinner. However, when the insulating film 13 is too thin, there is a problem that the insulation breakdown voltage between the ferromagnetic films M1 and M2 and the magnetoresistive elements R is insufficient. Considering this, it is preferable to set the thickness of the insulating film 13 to 0.05 μm or more and 0.3 μm or less.

[0042] As shown in Figure 1As shown, one end of the magnetoresistive strip S in the y direction is connected to the terminal electrode E1, and the other end is connected to the terminal electrode E2. More specifically, one end of the magnetoresistive strip S in the y direction is connected to the terminal electrode E1 without passing through other magnetoresistive elements to which the detection magnetic field is applied, and the other end of the magnetoresistive strip S in the y direction is connected to the terminal electrode E2 without passing through other magnetoresistive elements to which the detection magnetic field is applied. That is, in this embodiment, the magnetoresistive strip S is a straight line shape without a folded structure. The terminal electrodes E1 and E2 are connected to a detection circuit not shown in the figure, and the detection magnetic field can be measured based on the resistance value between the terminal electrodes E1 and E2.

[0043] Figure 3 This is an enlarged view for explaining the positional relationship between the magnetoresistive band S and the ferromagnetic film M1. Figure 1 The cross section shown corresponds to the line AA.

[0044] like Figure 3 As shown, the top surface of the insulating film 13 is not flat, but has projections and depressions reflecting the steps formed by the magnetoresistive element R and the hard magnetic body H. That is, when the thickness of the magnetoresistive element R is denoted as Tr and the thickness of the hard magnetic body H is denoted as Th, Tr<Th, and the hard magnetic body H is thicker. Therefore, when the insulating film 13 is formed by a film forming method that directly reflects the surface properties of the substrate, such as the ALD method, a concave portion is formed on the upper surface of the insulating film 13 in the portion covering the thin magnetoresistive element R. When the insulating film 13 is formed by the ALD method, and the thickness of the portion covering the magnetoresistive element R is denoted as T1 and the thickness of the portion covering the hard magnetic body H is denoted as T2, T1≒T2, and the height T3 of the step is T3≒Th-Tr. In addition, when the insulating film 13 is formed by the ALD method, the insulating film 13 is also formed on the side portion of the hard magnetic body H. Therefore, when the length of the magnetoresistive element R in the y direction is recorded as W1 and the length of the recessed portion of the insulating film 13 in the y direction is recorded as W2, W1>W2.

[0045] When the ferromagnetic films M1 and M2 are formed on the surface of the insulating film 13 having such a surface shape, the portion of the bottom surface B of the ferromagnetic films M1 and M2 that contacts the recessed portion of the insulating film 13 constitutes a protrusion B1 that protrudes toward the magnetoresistive element R. The width of the protrusion B1 in the y direction is also W2. In the present embodiment, since such a protrusion B1 is formed on the upper part of the magnetoresistive element R, the detection magnetic field is concentrated on the corners B2 located at both ends of the protrusion B1 in the y direction, and the detection magnetic field can be effectively applied to the magnetoresistive element R.

[0046] Thus, if an insulating film 13 is formed by a film-forming method such as the ALD method that directly reflects the surface properties of the substrate, protrusions B1 can be formed on the bottom surface B of the ferromagnetic films M1 and M2. However, the film-forming method for the insulating film 13 does not necessarily have to be a film-forming method such as the ALD method, and a film-forming method that does not easily reflect the surface properties of the substrate can also be used. For example, it can also be: as shown in Figure 4 (a), after forming a flat insulating film 13, as shown in Figure 4 (b), a groove 13a having a width W3 in the y direction narrower than the width W1 is formed on the insulating film 13. If irregularities are formed on the surface of the insulating film 13 by such a method, the positions and sizes of the protrusions B1 of the ferromagnetic films M1 and M2 can be arbitrarily designed.

[0047] As described above, in the magnetic sensor 1 of the present embodiment, since the hard magnetic body H and the ferromagnetic films M1 and M2 have overlapping portions, the magnetic bias applied to the magnetoresistive element R can be increased. Further, since the magnetoresistive element R and the ferromagnetic films M1 and M2 also have overlapping portions, and protrusions B1 are provided on the bottom surface B of the ferromagnetic films M1 and M2 in the portion overlapping with the magnetoresistive element R, a detection magnetic field can be effectively applied to the magnetoresistive element R.

[0048] In addition, in the magnetic sensor 1 of the present embodiment, since the magnetoresistive strip S has a linear shape without a folded-back structure, unlike the case where the magnetoresistive strip S has a shape in which it is folded back in a meandering shape, the relationship between the direction D of the magnetic bias and the current direction is fixed in all intervals. As a result, since irregular noise can be greatly reduced, a very weak magnetic field can be detected.

[0049] Furthermore, in the present embodiment, one end and the other end of the magnetoresistive strip S are respectively covered by end hard magnetic bodies H1 and H2. The end hard magnetic bodies H1 and H2 have a larger size in the y direction than the other hard magnetic body H. Moreover, since the ferromagnetic films M1 and M2 are provided at positions that do not overlap with the end hard magnetic bodies H1 and H2 when viewed from the z direction, the detection magnetic field collected by the ferromagnetic films M1 and M2 is not easily taken in by the end hard magnetic bodies H1 and H2. As a result, a detection magnetic field can be effectively applied to the magnetoresistive strip S.

[0050] Figures 5 to 7 They are graphs showing the relationships between the film thickness of the insulating film 13 and the sensitivities of the respective magnetoresistive elements R, the sensitivity of the magnetic sensor 1, and the noise of the magnetic sensor 1.

[0051] As Figure 5As shown, the sensitivity of each magnetoresistive element R decreases due to the provision of the ferromagnetic films M1 and M2, and the decrease becomes more significant as the film thickness of the insulating film 13 becomes thinner. This is because as the film thickness of the insulating film 13 becomes thinner, two adjacent hard magnetic bodies H are strongly magnetically coupled via the ferromagnetic films M1 and M2, and the magnetic bias becomes stronger. Therefore, the resistance value is not easily changed by the detected magnetic field. However, as Figure 6 shown, the higher the overall sensitivity of the magnetic sensor 1 becomes as the film thickness of the insulating film 13 becomes thinner. This means that the influence of the concentration of the magnetic field on the magnetoresistive element R caused by thinning the insulating film 13 is greater than the decrease in the sensitivity of each magnetoresistive element R caused by thinning the insulating film 13. In addition, as Figure 7 shown, the smaller the noise of the magnetic sensor 1 becomes as the film thickness of the insulating film 13 becomes thinner. This indicates that the noise has decreased due to the strengthening of the magnetic bias caused by thinning the insulating film 13.

[0052] As Figure 6 and Figure 7 shown, the higher the sensitivity and the lower the noise of the magnetic sensor 1 can be obtained as the film thickness of the insulating film 13 becomes thinner. However, there is no significant difference between the cases where the film thickness of the insulating film 13 is 0.1 μm and 0.05 μm, and it is considered that the effect is roughly saturated at around 0.1 μm. In addition, when the film thickness of the insulating film 13 is less than 0.05 μm, there is a problem of insufficient insulation breakdown voltage between the ferromagnetic films M1 and M2 and the magnetoresistive element R. Considering this, it can be said that the film thickness of the insulating film 13 is preferably designed to be 0.05 μm or more and 0.3 μm or less, and more preferably designed to be around 0.1 μm.

[0053] <Second Embodiment>

[0054] Figure 8 and Figure 9 are a schematic cross-sectional view and a schematic top view for explaining the structure of the magnetic sensor 2 according to the second embodiment of the present invention, respectively.

[0055] As Figure 8 and Figure 9 shown, the magnetic sensor 2 according to the second embodiment includes: insulating films 22 to 25 sequentially stacked on the sensor substrate 21; a compensation coil C provided on the surface of the insulating film 22; two magnetoresistive strips S1 and S2 provided on the surface of the insulating film 23; and three ferromagnetic films M11 to M13 provided on the surface of the insulating film 24.

[0056] The magnetoresistive bands S1 and S2 are each composed of a plurality of magnetoresistive elements R arranged in the y direction with a plurality of hard magnetic bodies H interposed therebetween. The direction D of the magnetic bias applied by the hard magnetic bodies H is the same in the magnetoresistive bands S1 and S2. Further, ferromagnetic films M11 and M12 are arranged in the x direction with a magnetic gap G1 extending in the y direction interposed therebetween, and ferromagnetic films M11 and M13 are arranged in the x direction with a magnetic gap G2 extending in the y direction interposed therebetween. Moreover, the magnetoresistive band S1 is disposed at a position overlapping with the magnetic gap G1, and the magnetoresistive band S2 is disposed at a position overlapping with the magnetic gap G2. The plurality of magnetoresistive elements R and the plurality of hard magnetic bodies H constituting the magnetoresistive band S1 have portions overlapping with the ferromagnetic films M11 and M12 with an insulating film 24 interposed therebetween. Further, the plurality of magnetoresistive elements R and the plurality of hard magnetic bodies H constituting the magnetoresistive band S2 have portions overlapping with the ferromagnetic films M11 and M13 with an insulating film 24 interposed therebetween.

[0057] Furthermore, the magnetic sensor 2 of the present embodiment includes: an external magnetic body 26 provided on the upper surface side of the sensor substrate 21; and an external magnetic body 27 covering the back surface and side surfaces of the sensor substrate 21. The external magnetic bodies 26 and 27 are formed of a soft magnetic material such as ferrite and function to efficiently collect the detection magnetic field in the z direction. The external magnetic body 26 is provided at a position covering the ferromagnetic film M11 with an insulating film 25 interposed therebetween. Thus, the detection magnetic field in the z direction collected by the external magnetic body 26 is taken into the ferromagnetic film M11 and distributed to the ferromagnetic films M12 and M13 through the magnetic gaps G1 and G2. Moreover, the detection magnetic field from the ferromagnetic film M11 toward the ferromagnetic film M12 is applied to the magnetoresistive band S1 in the -x direction, and the detection magnetic field from the ferromagnetic film M11 toward the ferromagnetic film M13 is applied to the magnetoresistive band S2 in the +x direction. That is, the detection magnetic fields are applied to the magnetoresistive bands S1 and S2 in opposite directions.

[0058] As Figure 10 shown, one end of the magnetoresistive band S1 in the y direction is connected to the terminal electrode E11, and the other end is connected to the terminal electrode E12. Further, one end of the magnetoresistive band S2 in the y direction is connected to the terminal electrode E13, and the other end is connected to the terminal electrode E11. Thus, the magnetoresistive bands S1 and S2 constitute a half-bridge circuit. In the present embodiment, the terminal electrodes E11 to E13 and the magnetoresistive bands S1 and S2 are also connected without passing through other magnetoresistive elements to which the detection magnetic field is applied. Thus, if a current flows from the terminal electrode E12 toward the terminal electrode E13, a current flows in the magnetoresistive band S1 in the direction indicated by the arrow I11, and a current flows in the magnetoresistive band S2 in the direction indicated by the arrow I12. That is, in the magnetoresistive bands S1 and S2, currents flow in the same direction. Moreover, since the detection magnetic fields are applied to the magnetoresistive bands S1 and S2 in opposite directions, if the potential of the terminal electrode E11 is monitored using a detection circuit (not shown), the direction and intensity of the detection magnetic field can be measured.

[0059] Furthermore, as Figure 10 shown, one end of the compensation coil C is connected to the terminal electrode E15, and the other end of the compensation coil C is connected to the terminal electrode E16. The compensation coil C is provided to apply a cancelling magnetic field to the magnetoresistive tapes S1, S2, thereby enabling so-called closed-loop control. The compensation coil C includes: an interval C1 extending in the y direction along the magnetoresistive tape S1; and an interval C2 extending in the y direction along the magnetoresistive tape S2. Moreover, when a current flows from the terminal electrode E15 to the terminal electrode E16, a current flows in the direction indicated by the arrow I21 in the interval C1, and a current flows in the direction indicated by the arrow I22 in the interval C2. That is, in the intervals C1, C2, currents flow in opposite directions to each other. Thereby, the detection magnetic fields applied to the magnetoresistive tapes S1, S2 in opposite directions to each other can be cancelled by the compensation coil C.

[0060] In this way, although the magnetic sensor 2 of the present embodiment includes two magnetoresistive tapes S1, S2, they do not have a sampling return structure and are wired such that currents flow in the same direction as each other. As a result, the relationship between the direction of the magnetic bias and the direction of the current is fixed and unchanged in all intervals of the magnetoresistive tapes S1, S2. As a result, since irregular noise can be greatly reduced, a very weak magnetic field can be detected.

[0061] <Third Embodiment>

[0062] Figure 11 is a schematic top view for explaining the structure of the magnetic sensor 3 according to the third embodiment of the present invention.

[0063] As Figure 11 shown, the magnetic sensor 3 according to the third embodiment differs from the magnetic sensor 2 according to the second embodiment in the following aspects: A magnetic gap G3 extending in the y direction is further formed between the ferromagnetic films M11, M12, a magnetic gap G4 extending in the y direction is further formed between the ferromagnetic films M11, M13, a magnetoresistive tape S3 is arranged at a position overlapping with the magnetic gap G3, and a magnetoresistive tape S4 is arranged at a position overlapping with the magnetic gap G4. Both the magnetoresistive tapes S3, S4 are composed of a plurality of magnetoresistive elements R arranged in the y direction with a plurality of hard magnetic bodies H interposed therebetween. The direction D of the magnetic bias applied by the hard magnetic body H is the same in the magnetoresistive tapes S1 to S4. The plurality of magnetoresistive elements R and the plurality of hard magnetic bodies H constituting the magnetoresistive tape S3 have portions overlapping with the ferromagnetic films M11, M12. In addition, the plurality of magnetoresistive elements R and the plurality of hard magnetic bodies H constituting the magnetoresistive tape S4 have portions overlapping with the ferromagnetic films M11, M13.

[0064] Thus, the detection magnetic field taken into the ferromagnetic film M11 by the external magnetic body 26 is distributed to the ferromagnetic films M12 and M13 through the magnetic gaps G1 to G4. Moreover, the detection magnetic field going from the ferromagnetic film M11 to the ferromagnetic film M12 is applied to the magnetoresistive bands S1 and S3 in the -x direction, and the detection magnetic field going from the ferromagnetic film M11 to the ferromagnetic film M13 is applied to the magnetoresistive bands S2 and S4 in the +x direction. That is, the detection magnetic field is applied to the magnetoresistive bands S1 and S3 and the magnetoresistive bands S2 and S4 in opposite directions.

[0065] As Figure 12 shown, one end of the magnetoresistive band S1 in the y direction is connected to the terminal electrode E11, and the other end is connected to the terminal electrode E12. In addition, one end of the magnetoresistive band S2 in the y direction is connected to the terminal electrode E13, and the other end is connected to the terminal electrode E11. Further, one end of the magnetoresistive band S3 in the y direction is connected to the terminal electrode E13, and the other end is connected to the terminal electrode E14. Moreover, one end of the magnetoresistive band S4 in the y direction is connected to the terminal electrode E12, and the other end is connected to the terminal electrode E14. Thus, the magnetoresistive bands S1 to S4 form a full-bridge circuit. In the present embodiment, the terminal electrodes E11 to E14 and the magnetoresistive bands S1 to S4 are also connected without passing through other magnetoresistive elements to which the detection magnetic field is applied. Thus, if a current flows from the terminal electrode E11 to the terminal electrode E14, currents flow in the directions indicated by the arrows I11 to I14 in the magnetoresistive bands S1 to S4, respectively. That is, in the magnetoresistive bands S1 to S4, currents flow in the same direction. Moreover, since the detection magnetic field is applied to the magnetoresistive bands S1, S3 and the magnetoresistive bands S2, S4 in opposite directions, if the voltage between the terminal electrodes E12 and E13 is monitored using a detection circuit (not shown), the direction and intensity of the detection magnetic field can be measured.

[0066] Further, as Figure 12 shown, one end of the compensation coil C is connected to the terminal electrode E15, and the other end of the compensation coil C is connected to the terminal electrode E16. The compensation coil C is provided to apply a canceling magnetic field to the magnetoresistive bands S1 to S4, and thus so-called closed-loop control can be performed. The compensation coil C includes: an interval C1 extending in the y direction along the magnetoresistive band S1; an interval C2 extending in the y direction along the magnetoresistive band S2; an interval C3 extending in the y direction along the magnetoresistive band S3; and an interval C4 extending in the y direction along the magnetoresistive band S4. Moreover, when a current flows from the terminal electrode E15 to the terminal electrode E16, currents flow in the directions indicated by the arrows I21 to I24 in the intervals C1 to C4, respectively. That is, in the intervals C1, C3 and the intervals C2, C4, currents flow in opposite directions. Thus, the detection magnetic field applied to the magnetoresistive bands S1, S3 and the magnetoresistive bands S2, S4 in different directions can be canceled using the compensation coil C.

[0067] Thus, although the magnetic sensor 3 of the present embodiment has four magnetoresistive bands S1 to S4, they do not adopt a folded-back structure and are wired so that current flows in the same direction for each of them. As a result, the relationship between the direction of magnetic bias and the direction of current is fixed throughout the entire range of the magnetoresistive bands S1 to S4. Accordingly, since irregular noise can be significantly reduced, a very weak magnetic field can be detected.

[0068] Above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to the above-described embodiments, and various changes can be made within the scope not exceeding the gist of the present invention. Of course, the embodiments obtained by making such changes are also included in the scope of the present invention.

[0069] For example, in the magnetic sensor 1 of the first embodiment, both the ferromagnetic films M1 and M2 have portions overlapping with the magnetoresistive band S. However, it may also be configured such that only one of the ferromagnetic films M1 and M2 has a portion overlapping with the magnetoresistive band S.

[0070] In addition, in the magnetic sensor 1 of the first embodiment, the ferromagnetic films M1 and M2 have portions overlapping with the plurality of magnetoresistive elements R and the plurality of hard magnetic bodies H constituting the magnetoresistive band S. However, it may also be configured such that the ferromagnetic films M1 and M2 do not overlap with the plurality of magnetoresistive elements R but have portions overlapping with the plurality of hard magnetic bodies H.

[0071] Furthermore, in the magnetic sensor 1 of the first embodiment, there are protrusions B1 on the bottom surface B of the ferromagnetic films M1 and M2. However, it is not essential to provide such protrusions B1 in the present invention, and the bottom surface B may also be flat.

[0072] [Reference Signs]

[0073] 1 to 3 Magnetic sensors;

[0074] 11 Sensor substrate;

[0075] 12, 13 Insulating films;

[0076] 13a Groove;

[0077] 21 Sensor substrate;

[0078] 22 to 25 Insulating films;

[0079] 26, 27 External magnetic bodies;

[0080] 27 External magnetic body;

[0081] B Bottom surface of ferromagnetic film;

[0082] B1 Protrusion;

[0083] B2 Corner

[0084] C Compensation coil;

[0085] C1 - C4 interval;

[0086] D Direction of magnetic bias;

[0087] E1, E2, E11 - E16 terminal electrodes;

[0088] G, G1 - G4 Magnetic gaps;

[0089] H Hard magnetic material;

[0090] H1, H2 End hard magnetic materials;

[0091] M1, M2, M11 - M13 Ferromagnetic films;

[0092] R Magnetoresistive element;

[0093] S, S1 - S4 Magnetoresistive bands;

[0094] φ Magnetic bias.

Claims

1. A magnetic sensor, characterized in that, Comprising: A first magnetoresistive strip composed of a plurality of magnetoresistive elements arranged in a first direction with a plurality of hard magnetic bodies having a magnetic bias applied therebetween; An insulating film covering the first magnetoresistive strip; And A first ferromagnetic film and a second ferromagnetic film provided on the insulating film and arranged in a second direction orthogonal to the first direction with a first magnetic gap extending in the first direction therebetween, When viewed from a third direction orthogonal to the first direction and the second direction, at least one of the first ferromagnetic film and the second ferromagnetic film has a portion overlapping the plurality of hard magnetic bodies with the insulating film therebetween and has a portion overlapping the plurality of magnetoresistive elements with the insulating film therebetween.

2. The magnetic sensor according to claim 1, characterized in that, When viewed from the third direction, both the first ferromagnetic film and the second ferromagnetic film have portions overlapping the plurality of hard magnetic bodies and the plurality of magnetoresistive elements with the insulating film therebetween.

3. The magnetic sensor according to claim 2, characterized in that, When viewed from the third direction, a portion of the first ferromagnetic film and the second ferromagnetic film overlapping the plurality of magnetoresistive elements has a protrusion with a bottom surface in contact with the insulating film protruding toward the plurality of magnetoresistive elements side, The width of the protrusion in the first direction is narrower than the width of each of the plurality of magnetoresistive elements in the first direction.

4. The magnetic sensor according to claim 1, characterized in that, The thickness of the insulating film is 0.05 μm or more and 0.3 μm or less.

5. The magnetic sensor according to claim 1, characterized in that, Further comprising: A second magnetoresistive strip composed of a plurality of magnetoresistive elements arranged in the first direction with a plurality of hard magnetic bodies having a magnetic bias applied therebetween; and A third ferromagnetic film provided on the insulating film, The first ferromagnetic film and the third ferromagnetic film are arranged in the second direction with a second magnetic gap extending in the first direction therebetween, When viewed from the third direction, at least one of the first ferromagnetic film and the third ferromagnetic film has a portion overlapping the plurality of hard magnetic bodies included in the second magnetoresistive strip with the insulating film therebetween.

6. The magnetic sensor according to claim 5, characterized in that, Further comprising: a compensation coil for applying a canceling magnetic field to the first magnetoresistive strip and the second magnetoresistive strip, The compensation coil includes: a first section extending in the first direction along the first magnetoresistive strip; and a second section extending in the first direction along the second magnetoresistive strip, The directions of the currents flowing in the first section and the second section are opposite to each other.

7. The magnetic sensor according to claim 5, characterized in that, Further comprising a third magnetoresistive strip and a fourth magnetoresistive strip composed of a plurality of magnetoresistive elements arranged in the first direction with a plurality of hard magnetic bodies having a magnetic bias applied therebetween, The first ferromagnetic film and the second ferromagnetic film further form a third magnetic gap extending in the first direction, The first ferromagnetic film and the third ferromagnetic film further form a fourth magnetic gap extending in the first direction, When viewed from the third direction, at least one of the first ferromagnetic film and the second ferromagnetic film has a portion overlapping the plurality of hard magnetic bodies included in the third magnetoresistive strip with the insulating film therebetween, When viewed from the third direction, at least one of the first ferromagnetic film and the third ferromagnetic film has a portion overlapping the plurality of hard magnetic bodies included in the fourth magnetoresistive strip with the insulating film therebetween.

8. The magnetic sensor according to claim 7, characterized in that, Further comprising a compensation coil for applying a canceling magnetic field to the first magnetoresistive strip to the fourth magnetoresistive strip, The compensation coil includes: a first section extending in the first direction along the first magnetoresistive strip; a second section extending in the first direction along the second magnetoresistive strip; a third section extending in the first direction along the third magnetoresistive strip; and a fourth section extending in the first direction along the fourth magnetoresistive strip, the directions of the currents flowing in the first section and the third section are the same as each other, the directions of the currents flowing in the second section and the fourth section are the same as each other, the directions of the currents flowing in the first section and the second section are opposite to each other.

9. The magnetic sensor according to any one of claims 1 to 8, characterized in that, A first terminal electrode and a second terminal electrode are further provided, one end of the first magnetoresistive strip in the first direction is connected to the first terminal electrode without passing through another magnetoresistive element to which the detection magnetic field is applied, the other end of the first magnetoresistive strip in the first direction is connected to the second terminal electrode without passing through another magnetoresistive element to which the detection magnetic field is applied.

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