JP7122836B2 - Magnetic and current sensors - Google Patents

Description

The present invention relates to a magnetic sensor and a current sensor including the magnetic sensor.

In fields such as motor drive technology for electric and hybrid cars, and infrastructure-related fields such as columnar transformers, where relatively large currents are handled, there is a demand for current sensors that can measure large currents without contact. there is As such a current sensor, one using a magnetic sensor for detecting an induced magnetic field from a current to be measured is known. Magnetoresistive elements such as GMR (Giant Magnetoresistive) elements are examples of magnetic detection elements for magnetic sensors.

Magnetoresistive elements have high detection sensitivity, but are characterized by high linearity and a relatively narrow detectable magnetic field strength range. For this reason, as in the current sensor shown in FIG. 3 of Patent Document 1, a magnetic shield is placed between the current to be measured and the magnetoresistive element, and the induced magnetic field substantially applied to the magnetoresistive element may be used to reduce the intensity of the magnetic field to be measured so that the magnitude of the magnetic field to be measured is within the magnetic field strength range that provides good detection characteristics.

By using the magnetic shield in this way, the strength of the magnetic field substantially applied to the magnetoresistive effect element is reduced, and it is realized to expand the measurement range of the magnetic field strength. It may cause hysteresis. In Patent Document 2, by providing a hard bias layer on the magnetic shield, this magnetic hysteresis is suppressed and the output linearity of the magnetoresistive effect element is improved.

WO2011/111493 WO2011/155261

When the magnetic field applied to the magnetic shield is as strong as several tens of mT, residual magnetization tends to occur in the magnetic shield even if the magnetic shield is made of a soft magnetic material. When the magnetic field based on the residual magnetization of the magnetic shield generated in this way is applied to the magnetoresistive effect element, it adversely affects the measurement accuracy of the magnetoresistive effect element, such as increasing the zero magnetic field hysteresis of the magnetoresistive effect element to the negative side. There is a risk of giving

In view of the current situation, the present invention provides a magnetic sensor including a magnetic shield and a magnetoresistive element, in which the measurement accuracy of the magnetoresistive element is less likely to decrease even when a large magnetic field is applied to the magnetic sensor. It is an object of the present invention to provide a magnetic sensor. Another object of the present invention is to provide a current sensor comprising such a magnetic sensor.

In one aspect of the present invention provided to solve the above problems, a magnetoresistive effect element and a magnetic field to be measured applied to the magnetoresistive effect element are arranged apart from the magnetoresistive effect element, and the strength of the magnetic field to be measured is a magnetic shield that attenuates, and a reset coil that resets the residual magnetization of the magnetic shield on the opposite side of the magnetic shield to the magnetoresistive element. A magnetic sensor. With such a configuration, even when a large magnetic field is applied to the magnetic shield, it is possible to reset the residual magnetization of the magnetic shield and reduce the hysteresis of the magnetoresistive element.

It is preferable that the reset coil is adjacent to the magnetic shield from the viewpoint of efficiently reducing the hysteresis of the magnetoresistive element.

From the viewpoint of efficiently reducing the hysteresis of the magnetoresistive element, it is preferable that the entire magnetoresistive element overlaps the magnetic shield in plan view.

The magnetic sensor may further include a magnetic balancing coil, and measure the strength of the magnetic field to be measured based on the current flowing through the magnetic balancing coil. In this case, it may be preferable that the magnetic balancing coil is a spiral coil and positioned adjacent to the magnetoresistive element between the magnetoresistive element and the magnetic shield.

According to another aspect of the present invention, there is provided a current sensor comprising the magnetic sensor described above, wherein the magnetic sensor uses the induced magnetic field of the current to be measured as the magnetic field to be measured.

According to the present invention, even when the applied magnetic field is large and residual magnetization occurs in the magnetic shield, the residual magnetization of the magnetic shield can be reset by the reset coil, and the influence of the applied magnetic field can be suppressed. Therefore, the effect of the return magnetic field due to residual magnetization on the magnetoresistive element can be suppressed. Therefore, a magnetic sensor is provided in which the measurement accuracy of the magnetoresistive effect element is less likely to deteriorate. A current sensor using such a magnetic sensor is also provided.

1 is a plan view conceptually showing the structure of a magnetic sensor according to an embodiment of the present invention; FIG. It is a top view which shows the shape of a reset coil. FIG. 3 is a cross-sectional view taken along line V1-V1 of FIGS. 1 and 2; FIG. 3 is a cross-sectional view taken along line V2-V2 of FIGS. 1 and 2; FIG. 2 is a cross-sectional view schematically showing a laminated structure provided in a magnetoresistive element; FIG. 4 is a plan view conceptually showing the structure of a magnetic sensor according to another embodiment of the present invention; FIG. 7 is a cross-sectional view taken along line V3-V3 of FIG. 6; 4 is a graph showing measurement results of zero magnetic field hysteresis before and after resetting the residual magnetization of the magnetic shield;

FIG. 1 is a plan view conceptually showing the structure of a magnetic sensor according to one embodiment of the present invention. In the figure, for the sake of convenience, the contour of the reset coil is indicated by a solid line, and the contour of the magnetic shield between the four magnetoresistive elements and the reset coil is indicated by a broken line. FIG. 2 is a plan view showing the outline of the structure of the reset coil, and the magnetic shield is indicated by broken lines as in FIG. 3 and 4 are cross-sectional views taken along lines V1-V1 and V2-V2 of FIG. FIG. 5 is a cross-sectional view schematically showing a laminated structure provided in the magnetoresistive effect element.

As shown in FIG. 1, a magnetic sensor 1 according to an embodiment of the present invention includes magnetoresistive elements 11 to 14 (hereinafter collectively referred to as "four magnetoresistive elements"). ), a magnetic shield 15 and a reset coil 20 .

Each of the four magnetoresistance effect elements of the magnetic sensor 1 has a meandering shape (a shape formed by connecting a plurality of long patterns extending in the X1-X2 direction so as to fold back). element). The sensitivity axis direction P of each of the four magnetoresistive effect elements is indicated by an arrow in FIG. The sensitivity axis direction P of the effect element 12 and the magnetoresistive effect element 13 is set to face the Y1-Y2 direction Y2 side.

As shown in FIG. 5, each of the four magnetoresistive elements (magnetoresistive element 11 to magnetoresistive element 14) has a configuration in which a pinned magnetic layer 31, a nonmagnetic layer 32, and a free magnetic layer 33 are laminated. It has The resistance value changes depending on the relative relationship between the magnetization directions of the pinned magnetic layer 31 whose magnetization direction is fixed in the sensitivity axis direction P and the free magnetic layer 33 whose magnetization direction is changed by an external magnetic field. The direction and strength of the external magnetic field can be detected by detecting the change in this resistance value.

Barkhausen noise occurs when the domain wall moves inside the free magnetic layer 33 made of a soft magnetic material. Therefore, in order to stabilize the output of the magnetic sensor 1, an exchange bias magnetic field using an exchange coupling magnetic field with the antiferromagnetic layer 34 is applied in a direction perpendicular to the sensitivity axis direction P of each of the four magnetoresistance effect elements. The magnetization directions B (see FIG. 1) of the free magnetic layers 33 of the four magnetoresistive elements can be aligned by the exchange bias magnetic field applied to the free magnetic layers 33 . A hard bias magnetic field may be applied to the free magnetic layer 33 using a permanent magnet instead of the exchange bias magnetic field using the exchange coupling magnetic field.

As shown in FIG. 1, the wiring 5 connected to the input terminal 5a is connected to one end of the magnetoresistive element 11, and the other end of the magnetoresistive element 11 and one end of the magnetoresistive element 12 are connected in series. Then, the other end of the magnetoresistive element 12 is connected to the ground terminal 6a through the wiring 6. As shown in FIG. The wiring 5 connected to the input terminal 5a branches in the middle and is also connected to one end of the magnetoresistive element 13, and the other end of the magnetoresistive element 13 and one end of the magnetoresistive element 14 are connected in series. , the other end of the magnetoresistive element 14 is connected to the ground terminal 6a through the wiring 6. As shown in FIG. The first terminal 7a for measuring the potential of the middle point is connected between the other end of the magnetoresistive element 11 and the one end of the element 12 by the wiring 7, and the terminal 8a for measuring the second potential of the middle point is connected to the magnetoresistive element. A wiring 8 is connected between the other end of the effect element 13 and one end of the magnetoresistive effect element 14 . By comparing the potential of the first midpoint potential measuring terminal 7a and the potential of the second midpoint potential measuring terminal 8a, the induced magnetic field (magnetic field to be measured) of the current Io to be measured flowing through the current line 40 can be determined. Intensity and orientation can be measured.

FIG. 3 is a cross-sectional view taken along line V1-V1 of FIGS. 1 and 2. FIG. FIG. 3 is a cross section obtained by cutting the magnetic sensor 1 along a plane normal to the direction along the long axis direction (X1-X2 direction) of the plurality of elongated patterns forming the meandering shape of the magnetoresistive effect element 11. It is a diagram. In the figure, the meandering magnetoresistive effect element 11 is indicated by a rectangle for convenience. The Y1-Y2 direction, which is one of the directions in the cross section, is the sensitivity axis direction P of the magnetoresistive effect element 11 (the direction of the Y1-Y2 direction on the Y1 side). The magnetoresistive element 11 is formed on the substrate 29 and covered with an insulating layer IM made of an insulating material (specific examples include alumina, silicon nitride, etc.).
The magnetic shield 15 is arranged above the magnetoresistive element 11 (on the Z1-Z2 direction Z1 side) and spaced apart from the magnetoresistive element 11 . The distance between the magnetic shield 15 and the magnetoresistive element 11 is adjusted by the thickness of the insulating layer IM located therebetween.

In the magnetic sensor 1 according to one embodiment of the present invention, the magnetic shield 15 attenuates the intensity of the magnetic field to be measured applied to the four magnetoresistive effect elements. As shown in FIGS. 1 and 2, the magnetic shield 15 extends in a direction (X1-X2 direction) orthogonal to the sensitivity axis direction P (Y1-Y2 direction) in plan view (as seen from the Z1-Z2 direction). , and the magnetoresistive elements 11 to 14 are arranged so as to overlap within this rectangle.

For example, as shown in FIG. 3, the magnetic shield 15 includes an underlying layer 151 made of a soft magnetic material located at the lower end (Z1-Z2 direction Z2 side end) of the magnetic shield 15, and an underlying layer 151 (Z1- and a soft magnetic layer 152 formed in the Z2 direction (Z1 side).

Since the X1-X2 direction is the longitudinal direction of the magnetic shield 15, magnetization in the Y1-Y2 direction, which is the short side, is more difficult than in the X1-X2 direction, which is the longitudinal direction, due to the shape magnetic anisotropy effect. However, when the external magnetic field is strong, residual magnetization M0 may occur in the Y1-Y2 direction. FIG. 3 shows, as an example, a case where the residual magnetization M0 is generated in the Y1-Y2 direction and the Y1 direction. When the residual magnetization M0 is generated in the magnetic shield 15 in this way, the magnetic field (return magnetic field RM0) based on the residual magnetization M0 is directed in the direction opposite to the direction of the residual magnetization M0 (Y1-Y2 direction Y2 direction). is applied to This return magnetic field RM0 causes an offset and lowers the measurement accuracy of the magnetic sensor 1. FIG. Even in such a case, a current is passed through the reset coil 20 to generate a magnetic field that resets the residual magnetization M0 of the magnetic shield 15, returning the magnetic shield 15 to the state before the strong external magnetic field was applied. be able to. As a result, application of the return magnetic field RM0 based on the residual magnetization M0 to the magnetoresistive element 11 can be prevented or suppressed. Therefore, the measurement accuracy of the magnetic sensor 1 including the magnetoresistive element 11 is improved compared to the case without the reset coil 20 for resetting the magnetization state of the magnetic shield 15 .

As shown in FIG. 2, the reset coil 20 is composed of a spiral planar coil 20A and a spiral planar coil 20B arranged symmetrically with respect to a straight line C in the Y1-Y2 direction between them. It is One end 20AC positioned inside the spiral-shaped planar coil 20A is connected to a terminal 21A provided at the center of the planar coil 20A, and one end 20BC positioned inside the spiral-shaped planar coil 20B is provided at the center of the planar coil 20B. connected to the terminal 21B. One end 20AC of the planar coil 20A is located near the end of the magnetic shield 15 on the X1-X2 direction X2 side in plan view, and one end 20BC of the planar coil 20B is located in the X1-X2 direction of the magnetic shield 15 in plan view. It is located near the end on the X1 side. Further, the other end 20AE located outside the spiral planar coil 20A and the other end 20BE located outside the spiral planar coil 20B are both connected to the terminal 22 located on the straight line C in plan view. It is That is, the winding directions of the planar coil 20A and the planar coil 20B, both of which have a spiral shape, are opposite to each other. Specifically, in the planar coil 20A, the winding direction of the coil is clockwise from the one end 20AC located inside to the other end 20AE located outside, and in the planar coil 20B, the winding direction is clockwise from the one end 20BC located inside. The winding direction of the coil to the located other end 20BE is counterclockwise.

In the reset coil 20 arranged as described above, as shown in FIG. , a magnetic field in the same direction is applied to the entire magnetic shield 15 . This magnetic field can reset the residual magnetization effects of the external magnetic field. Specifically, as described above, since the coil winding directions of the planar coil 20A and the planar coil 20B are opposite to each other, the X1-X2 direction of the reset coil 20 in plan view (Z1-Z2 direction) is A current flows from the Y1 side to the Y2 side in the Y1-Y2 direction in any of the coils in the portion overlapping the longitudinal rectangular magnetic shield 15 (indicated by the thick dotted line in FIG. 2). Therefore, the induced magnetic field of these currents is applied to the magnetic shield 15 as a whole as a magnetic field in the direction of the white arrow indicated by the dashed line (X1-X2 direction X2 direction) (FIGS. 2 and 3). See Figure 4).

The magnetic sensor 1 of the present invention is provided with a reset coil 20 for resetting (initializing) characteristic fluctuations occurring in the magnetic shield 15 after a strong magnetic field is applied. A reset magnetic field generated by applying a short current to the reset coil 20 at regular intervals can remove residual magnetization M0 generated by a strong external magnetic field from the magnetic shield 15 .

As shown in FIG. 1, a bias magnetic field B is applied to the four magnetoresistive elements in order to suppress multi-domain formation of the free magnetic layer 33 (see FIG. 5) due to a strong external magnetic field. If the bias magnetic field B is increased, it is effective for suppressing multi-domain formation of the free magnetic layer 33, but the first midpoint potential measuring terminal 7a and the second midpoint potential measuring terminal 8a (see FIG. 1) ), the response speed is lowered. Therefore, from the viewpoint of improving the sensitivity of the magnetic sensor 1, increasing the bias magnetic field B is not preferable.

The purpose of the reset coil 20 of the magnetic sensor 1 of the present invention is to reset the magnetic shield 15 . Therefore, a reset coil 20 is provided on the opposite side of the magnetic shield 15 from the four magnetoresistive elements. However, even if the magnetic field generated by the reset coil 20 is applied not only to the magnetic shield 15 but also to the free magnetic layers 33 of the four magnetoresistive elements overlapping the magnetic shield 15 in plan view (as seen from the Z1-Z2 direction). good. By applying a magnetic field also to the free magnetic layer 33 at predetermined time intervals by the reset coil 20, the bias magnetic field B for suppressing multi-domainization can be weakened, so that the sensitivity of the magnetic sensor 1 can be improved. . Further, when the material of the magnetic shield 15 is a permalloy plated film, there is an advantage that the applicable composition range can be expanded.

The reset coil 20 is preferably positioned adjacent to the magnetic shield 15 as shown in FIG. With this configuration, the effect of resetting the residual magnetization M0 of the magnetic shield 15 can be enhanced. Therefore, it is possible to prevent or suppress the magnetic field (return magnetic field RM0) based on the residual magnetization M0 of the magnetic shield 15 from being applied to the magnetoresistive element 11. FIG.

As described above, it is preferable that the entire four magnetoresistive elements overlap the magnetic shield 15 in plan view (as seen from the Z1-Z2 direction). In this case, the return magnetic field RM0 based on the residual magnetization M0 of the magnetic shield 15 can be more stably prevented or suppressed from being applied to the four magnetoresistive elements.

The underlayer 151 and the soft magnetic layer 152 are composed of a soft magnetic material containing iron group elements such as Fe, Co, and Ni. The thickness of the underlying layer 151 is set arbitrarily. The thickness of the soft magnetic layer 152 is arbitrarily set within a range in which the magnetic shield 15 has a predetermined magnetic shielding function. Non-limiting examples of the thickness of the soft magnetic layer 152 include 1 μm to 50 μm. The thickness of the soft magnetic layer 152 may be preferably 5 μm to 30 μm, and more preferably 10 μm to 25 μm. .

The aspect ratio of the magnetic shield 15 is the ratio of the length in the longitudinal direction (X1-X2 direction) of the magnetic shield 15 to the length in the lateral direction (Y1-Y2 direction). By increasing the aspect ratio of the magnetic shield 15 , the anisotropic magnetic field Hk of the magnetic shield 15 is increased, and the linear region of the magnetization curve of the magnetic shield 15 can be further expanded in the sensitivity axis direction of the magnetic sensor 1 . As a result, the linear region of the output of the magnetic sensor 1 is expanded, and the dynamic range of the magnetic sensor 1 can be further expanded.

In the magnetic shield 15 shown in FIG. 1, an oxidation protective layer PL made of tantalum (Ta) or the like is further formed on the soft magnetic layer 152 (Z1-Z2 direction Z1 side).

The method of manufacturing the magnetic shield 15 is arbitrary. As a non-limiting example, the base layer 151 is formed by a dry process such as sputtering or a wet process such as electroless plating. For example, the soft magnetic layer 152 is formed by electroplating using the stratum 151 as a conductive layer.

FIG. 6 is a plan view conceptually showing the structure of a magnetic sensor according to another embodiment of the present invention. FIG. 7 is a cross-sectional view along V3-V3 in FIG. A magnetic sensor 1A shown in FIGS. 6 and 7 includes magnetoresistive elements 11 to 14, a magnetic shield 15 and a reset coil 20, similarly to the magnetic sensor 1 shown in FIG. A magnetic balancing coil (spiral coil) 16 having a spiral shape is provided between the resistance effect element and the magnetic shield 15 . In FIG. 6, the contour of the magnetic balancing coil 16 is indicated by a thick dashed line. Coil wiring is arranged so as to circle within the XY plane of the region indicated by the dashed line. In FIG. 7, cross sections of a plurality of winding coil wires in the magnetic balancing coil 16 are shown aligned in the Y1-Y2 direction. The magnetic balancing coil 16 is positioned between the four magnetoresistive elements and the magnetic shield 15 so that the induced magnetic field that cancels the external magnetic field applied while being attenuated by the magnetic shield 15 is relatively small. It can be caused by electric current. Therefore, it is possible to operate the magnetic balance type magnetic sensor with low power consumption.

In the above embodiment, the specific example is the case where the four magnetoresistive elements included in the magnetic sensors 1 and 1A are GMR elements, but the present invention is not limited to this. In one non-limiting example, the magnetoresistive element is one selected from the group consisting of an anisotropic magnetoresistive element (AMR element), a giant magnetoresistive element (GMR element), and a tunnel magnetoresistive element (TMR element). It consists of the above elements.

When the pinned magnetic layers of the GMR elements constituting the four magnetoresistive elements of the magnetic sensor 1 have a self-pinned structure, the pinned magnetic layers can be magnetized by film formation in a magnetic field. No heat treatment in a magnetic field is required after the film. Therefore, GMR elements having different magnetization directions of fixed magnetic layers can be arranged on the same substrate, and a full bridge circuit can be configured on one substrate.

A magnetic sensor 1, 1A having a magnetoresistive element according to one embodiment of the present invention can be suitably used as a current sensor.

Specific examples of current sensors according to an embodiment of the present invention include magnetic proportional current sensors and magnetic balance current sensors.

A specific example of the magnetic proportional current sensor is the case of using the magnetic sensor 1 shown in FIGS. Z1-Z2 direction (Z1 side), the current line 40 through which the current Io to be measured flows extends in the X1-X2 direction (see FIG. 1). The induced magnetic field of the current Io to be measured, which serves as the magnetic field to be measured, is applied to the magnetoresistive effect element 11 in a direction along the sensitivity axis direction P (Y1-Y2 direction). Since part of the magnetic field to be measured passes through the magnetic shield 15 having a higher magnetic permeability, the intensity of the magnetic field to be measured substantially applied to the magnetoresistive effect element 11 can be reduced. Therefore, it is possible to expand the measurement range of the magnetic sensor 1 . Moreover, the residual magnetization M0 of the magnetic shield 15 is suppressed or removed by the reset coil 20 provided on the opposite side (Z1-Z2 direction Z1 side) of the magnetoresistive effect element 11 to the magnetoresistive effect element 14 with respect to the magnetic shield 15. be able to. Therefore, the reset coil 20 can suppress the effect of the return magnetic field RM0 based on the residual magnetization M0 on the four magnetoresistive elements.

In a preferred example, the magnetic proportional current sensor 2 has four magnetoresistive elements and has a magnetic field detection bridge circuit with two outputs that produce a potential difference according to the magnetic field to be measured, which is the induced magnetic field of the current Io to be measured. (See Figures 1 and 2). In the magnetic proportional current sensor 2 having this bridge circuit, the current Io to be measured is measured from the potential difference output from the magnetic field detection bridge circuit according to the magnetic field to be measured.

A specific example of the magnetic balance current sensor is a magnetic balance current sensor 2A using the magnetic sensor 1A shown in FIGS. (Z1-Z2 direction Z1 side), the current line 40 through which the current Io to be measured flows extends in the X1-X2 direction (see FIG. 6). The induced magnetic field of the current Io to be measured, which is the magnetic field to be measured, is applied to the magnetoresistive effect element 11 in the direction along the sensitivity axis direction P (Y1-Y2 direction). Since part of the magnetic field to be measured passes through the magnetic shield 15 having a higher magnetic permeability, the intensity of the magnetic field to be measured substantially applied to the magnetoresistive effect element 11 can be reduced. Therefore, the amount of current flowing through the magnetic balancing coil 16 can be reduced to generate an induced magnetic field that cancels the magnetic field generated by the current Io to be measured that is substantially applied to the magnetoresistive element 11. Power saving of the sensor is realized.

In a preferred example, the magnetic balance type current sensor 2A is provided with four magnetoresistive effect elements, and includes a magnetic field to be measured composed of an induced magnetic field from the current Io to be measured and a magnetic balancing magnetic field applied to cancel the magnetic field to be measured. A magnetic sensor 1A is used that has a magnetic field detection bridge circuit with two outputs that produce a potential difference depending on the induced magnetic field from the coil 16 (see FIG. 6). In the magnetic balance current sensor 2A having this bridge circuit, the measured current Io is measured based on the current flowing through the magnetic balance coil 16 when the potential difference output from the magnetic field detection bridge circuit becomes zero.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is meant to include all design changes and equivalents that fall within the technical scope of the present invention.

EXAMPLES The present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

(Example)
A magnetic proportional magnetic sensor having a structure similar to the cross-sectional structure shown in FIGS. 3 and 4 was produced. The magnetoresistive element was a GMR element. The magnetic shield has a planar shape of 800 μm × 140 μm and is formed by sputtering a base layer made of NiFe and having a thickness of 100 nm. Further, an oxidation protection layer made of Ta and having a thickness of 10 nm was formed by sputtering. Using the magnetic shield as a reference, a plurality of magnetic sensors were manufactured in which a reset coil for resetting the magnetic shield was provided on the side opposite to the magnetoresistive effect element.

(Measurement example) Measurement of zero magnetic field hysteresis For the magnetic sensor produced in the example, the zero magnetic field hysteresis ZH (unit: %/FS) was measured before and after applying a reset magnetic field of 20 mT by a reset coil. The zero magnetic field hysteresis ZH was obtained from the hysteresis loop measured while changing the external magnetic field with the maximum strength of the applied external magnetic field (maximum applied magnetic field) set to ±18 mT. The zero-field hysteresis ZH is the magnitude of the output at zero magnetic field (maximum positive It is the ratio (unit: %) of value when changing from application of magnetic field to zero applied magnetic field - value when changing from application of negative maximum magnetic field to zero applied magnetic field). FIG. 8 shows the measurement results. The figure shows the average and standard deviation (3σ) of the measurement results of 100 magnetic sensors.

As shown in FIG. 8, the zero magnetic field hysteresis ZH of the magnetic sensor has an average value of −0.23% and a standard deviation (3σ) of 0.29% before applying the reset magnetic field, and after applying the reset magnetic field , the average value was 0.024%, and the standard deviation (3σ) was 0.034. By resetting the external magnetic field of the magnetic shield in this way, the zero magnetic field hysteresis of the magnetic sensor was significantly improved.
This is because the residual magnetization of the magnetic shield is reset, thereby reducing the influence of the return magnetic field due to the residual magnetization on the magnetoresistive effect element.

A magnetic sensor equipped with a magnetoresistive element according to an embodiment of the present invention is suitably used as a component of a current sensor for infrastructure equipment such as a columnar transformer, or a component of a current sensor for electric vehicles, hybrid vehicles, and the like. sell.

1, 1A magnetic sensor 2 magnetic proportional current sensor 2A magnetic balance current sensor 11, 12, 13, 14 magnetoresistive effect elements 5, 6, 7, 8 wiring 5a input terminal 6a ground terminal 7a first midpoint potential measurement terminal 8a second midpoint potential measuring terminal 40 current line Io current to be measured IM insulating layer 15 magnetic shield 151 underlying layer 152 soft magnetic layer 16 magnetic balancing coil (spiral coil)
20, 20A, 20B Reset coils 20AC, 20BC One end 20AE, 20BE The other end 21A, 21B, 22 Terminal C Straight line 31 Pinned magnetic layer 32 Nonmagnetic layer 33 Free magnetic layer 34 Antiferromagnetic layer P Sensitivity axis direction PL Oxidation protection layer 29 Substrate M0 Residual magnetization RM0 Return magnetic field

Claims (6)

A magnetic sensor comprising a magnetoresistive element and a magnetic shield spaced apart from the magnetoresistive element and attenuating the strength of a magnetic field to be measured applied to the magnetoresistive element,
A reset coil for resetting residual magnetization of the magnetic shield is provided on the opposite side of the magnetic shield to the magnetoresistive element,
The magnetic shield is formed in an elongated shape having a longitudinal direction perpendicular to the sensitivity axis direction of the magnetoresistive effect element,
In plan view, the entire magnetoresistive element overlaps the magnetic shield,
The induced magnetic field of the current flowing through the reset coil is applied to the entire magnetic shield in a direction along the longitudinal direction, and is also applied to the free magnetic layer of the magnetoresistance effect element. magnetic sensor. 2. The magnetic sensor of claim 1, wherein the reset coil is adjacent to the magnetic shield. The reset coil is configured by arranging a pair of planar coils having a spiral shape along the longitudinal direction of the magnetic shield, one of the pair of planar coils is wound clockwise, and the pair of planar coils is wound in a clockwise direction. 3. The magnetic sensor according to claim 1 or 2, wherein the other of the is formed counterclockwise. 4. The magnetic sensor according to any one of claims 1 to 3, further comprising a magnetic balancing coil, and measuring the intensity of the magnetic field to be measured based on the current flowing through the magnetic balancing coil. 5. The magnetic sensor according to claim 4, wherein said magnetic balancing coil is a spiral coil and is positioned adjacent to said magnetoresistive element between said magnetoresistive element and said magnetic shield. A current sensor comprising the magnetic sensor according to any one of claims 1 to 5, wherein the magnetic sensor uses an induced magnetic field of a current to be measured as the magnetic field to be measured.

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