Magnetic sensor, control method of magnetic sensor, and control program of magnetic sensor

Abstract

To provide a magnetic sensor in which reproducibility of a hysteresis loop with respect to a change in an external magnetic field and linearity in a linear region are enhanced.SOLUTION: A magnetic sensor includes a magnetoresistance effect element connected between a power supply and a ground, the magnetoresistance effect element including a fixed layer having fixed magnetization, a free layer having free magnetization that forms a vortex configuration in a state where there is no external magnetic field, and a nonmagnetic layer provided between the fixed layer and the free layer, and a current changing circuit that changes a current value of a current flowing through the magnetoresistance effect element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a magnetic sensor, a method for controlling a magnetic sensor, and a program for controlling a magnetic sensor. [Background technology]

[0002] Magnetic sensors using magnetoresistive elements with a vortex free layer have attracted attention. The vortex free layer forms a vortex whose magnetization is stable in the absence of an external magnetic field, and therefore has the characteristic of having small magnetic hysteresis (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2022-529884 Summary of the Invention [Problem to be solved by the invention]

[0004] In a magnetoresistive element with a vortex free layer, the core position, which is the center of the magnetization vortex, fluctuates in response to an external magnetic field. However, if there are defects in the free layer that hinder magnetization change, such as grain boundaries or crystal defects, the core is temporarily trapped at that position, preventing smooth fluctuations in response to the external magnetic field. This can degrade the reproducibility of the hysteresis loop and impair the usefulness of a magnetoresistive element with a vortex free layer. Therefore, the magnetoresistive element in Reference 1 forms an indent at the end of the free layer, allowing the core to be reproducibly formed at the indent. This ensures that the core's round-trip fluctuation path remains consistent even if defects exist in the ferromagnetic layer that makes up the free layer. While this method can improve the reproducibility of the magnetic sensor, the core's fluctuating response to changes in the external magnetic field is hindered if the core is trapped by the defect, impairing the linearity of the magnetic sensor.

[0005] The present disclosure provides a magnetic sensor with improved reproducibility of the hysteresis loop in response to changes in an external magnetic field and improved linearity in the linear region. [Means for solving the problem]

[0006] A magnetic sensor in a first aspect of the present disclosure comprises a magnetoresistive element connected between a power supply and ground, the magnetoresistive element having a fixed layer with fixed magnetization, a free layer with free magnetization that forms a vortex configuration in the absence of an external magnetic field, and a non-magnetic layer provided between the fixed layer and the free layer, and a current change circuit that changes the current value of the current flowing through the magnetoresistive element.

[0007] A control method for a magnetic sensor in a second aspect of the present disclosure includes a detection step of causing a magnetoresistive element connected between a power source and ground, the magnetoresistive element having a fixed layer with fixed magnetization, a free layer with free magnetization that forms a vortex configuration in the absence of an external magnetic field, and a non-magnetic layer provided between the fixed layer and the free layer, to detect an external magnetic field without causing a current change circuit capable of changing the current value of a current flowing through the magnetoresistive element to change the current value, and a change step of causing the current change circuit to change the current value during a non-detection period in which an external magnetic field is not detected.

[0008] A control program for a magnetic sensor in a third aspect of the present disclosure causes a computer to execute a detection step of causing a magnetoresistive element connected between a power source and ground, the magnetoresistive element having a fixed layer with fixed magnetization, a free layer with free magnetization that forms a vortex configuration in the absence of an external magnetic field, and a non-magnetic layer provided between the fixed layer and the free layer, to detect an external magnetic field without changing the current value using a current change circuit that can change the current value of the current flowing through the magnetoresistive element, and a change step of causing the current change circuit to change the current value during a non-detection period when no external magnetic field is detected. [Effects of the Invention]

[0009] The present disclosure makes it possible to provide a magnetic sensor that improves the reproducibility of the hysteresis loop in response to changes in the external magnetic field and the linearity in the linear region. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a conceptual diagram illustrating an overall configuration of a magnetic sensor according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a diagram showing the fluctuation of the vortex configuration of free magnetization with respect to a change in the external magnetic field in a hypothetical magnetoresistive element. [Figure 3] FIG. 10 is a diagram showing the magnetization curve of the free layer of a hypothetical magnetoresistive element. [Figure 4] FIG. 10 is a diagram showing an example of core fluctuations in response to changes in an external magnetic field in a realistic magnetoresistive element. [Figure 5] FIG. 10 is a diagram showing an example of a magnetization curve in the linear region of a realistic magnetoresistive element. [Figure 6] FIG. 2 is a diagram showing an example of a magnetization curve of a free layer in a linear region of a magnetoresistive element according to an embodiment of the present disclosure. [Figure 7] FIG. 10 is a diagram showing changes over time in the value of a current flowing through a magnetoresistive element. [Figure 8] FIG. 4 is a flow diagram of a control process executed by a control module. [Figure 9] FIG. 10 is a conceptual diagram showing the overall configuration of a magnetic sensor according to a modified example of the present disclosure. [Figure 10] 10 is a diagram showing a change over time in the value of a current flowing through a magnetoresistive effect element according to a modified example. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present disclosure will be described with reference to the accompanying drawings. In each drawing, components with the same reference numerals have the same or similar configurations. Furthermore, when multiple structures with the same or similar configurations exist in each drawing, some may be referenced with the same reference numerals and others may not be referenced with the same reference numerals to avoid complication. Note that the invention according to the claims is not limited to the following embodiment. Furthermore, not all of the configurations described in the embodiment are necessarily essential as means for solving the problem.

[0012] FIG. 1 is a conceptual diagram showing the overall configuration of a magnetic sensor 100 according to this embodiment. The magnetic sensor 100 mainly includes two magnetoresistive effect elements 110, a current changing circuit 130, an amplifier circuit 140, and a control module 150. The two magnetoresistive effect elements 110 are connected in series with each other between a constant voltage source and ground to form a half-bridge circuit. The constant voltage source supplies a constant supply voltage V to the half-bridge circuit. SUP The two magnetoresistance effect elements 110 are arranged so that the magnetization of their pinned layers faces in opposite directions so that their magnetic detection axes are opposite to each other, and their resistance values ​​vary in a complementary manner in response to the external magnetic field within a linear region. Therefore, the output voltage at the connection point of the two magnetoresistance effect elements 110 varies in response to the strength of the external magnetic field. Note that the supply voltage V SUP is known, it does not have to be a constant voltage, and may be an AC voltage supplied from an AC power source. In this case, the output voltage at the connection point of the two magnetoresistance effect elements 110 is determined by the strength of the external magnetic field and the known supply voltage V SUP It varies according to.

[0013] In the following description, the magnetoresistive element 110 employed in the magnetic sensor 100 is assumed to be a TMR (tunneling magnetoresistive) element, but it may be a CPP (current-perpendicular-to-plane) spin-valve magnetoresistive element (MR element), such as a GMR (giant magnetoresistive) element. In the case of a CPP magnetoresistive element, the current magnetic field generated by the flow of current in the magnetoresistive element portion is generated in the direction of vortex rotation or the opposite direction of vortex rotation. In this embodiment, the two magnetoresistive elements 110 constituting the half-bridge circuit both have the same structure, but magnetoresistive elements of different structures or types may be combined.

[0014] The magnetoresistive element 110 mainly includes a fixed layer 111, a free layer 112, a non-magnetic layer 113, and a lead electrode 114. The fixed layer 111 is a so-called pinned layer having a fixed magnetization 210 whose magnetization is fixed in one direction. The two magnetoresistive elements 110 are adjusted so that the magnetization directions of the fixed magnetizations 210 are opposite to each other when fixed to the substrate, for example, so that the resistance changes in response to an external magnetic field are opposite to each other. The fixed layer 111 may be formed to have, for example, a cylindrical or elliptical cylindrical shape as a whole.

[0015] The free layer 112 is a so-called free layer having free magnetization 220 that forms a vortex configuration in the absence of an external magnetic field. Like the fixed layer 111, the free layer 112 also has, for example, a cylindrical or elliptical cylindrical shape as a whole. The nonmagnetic layer 113 is sandwiched between the fixed layer 111 and the free layer 112, and in this embodiment, which employs a TMR element as the magnetoresistive element 110, it is a tunnel barrier layer. It is preferable that the fixed layer 111, nonmagnetic layer 113, and free layer 112, stacked in this order, also have a cylindrical or elliptical cylindrical shape as a whole. Note that the shapes of the fixed layer 111, nonmagnetic layer 113, and free layer 112 do not necessarily have to be identical.

[0016] The pinned layer 111 and the free layer 112 are made of ferromagnetic films containing, for example, NiFe, NiFeCo, Fe, FeCo, Co, CoFeB, or the like. The non-magnetic layer 113 is a thin insulating layer, and its thickness is adjusted to allow electron tunneling between the pinned layer 111 and the free layer 112. In the magnetoresistive element 110 prepared in this manner, the resistance between the pinned layer 111 and the free layer 112 decreases as the free magnetization 220 in the same direction as the magnetization direction of the pinned magnetization 210 increases, and the resistance between the pinned layer 111 and the free layer 112 increases as the free magnetization 220 in the opposite direction to the magnetization direction of the pinned magnetization 210 increases.

[0017] The lead electrode 114 is a columnar electrode directly connected to the end face 112a of the free layer 112 opposite the contact face that contacts the nonmagnetic layer 113, and has a contact surface smaller in area than the end face 112a. When the contact face of the lead electrode 114 is smaller in area than the end face 112a, for example, the influence (e.g., stress) on the free layer 112 caused by the junction between the lead electrode 114 and the end face 112a is reduced. Furthermore, compared to when the contact face is large, a smaller contact face limits, for example, the path through which the current flows, making it possible to effectively apply a current magnetic field to the free layer. By employing a lead electrode 114 with such a shape, fluctuations in the vortex configuration of the free magnetization 220 of the free layer 112 are suppressed, resulting in a magnetic sensor with higher linearity.

[0018] The two magnetoresistive elements 110 are connected to a constant supply voltage V SUP Since the magnetoresistive effect elements 110 are connected in series between a constant voltage source supplying a current and ground, the current value of each magnetoresistive effect element 110 is determined based on the combined resistance of the magnetoresistive effect elements 110, which varies depending on the magnitude of the external magnetic field. In this embodiment, a current modification circuit 130 is provided that forcibly modifies the current value of each magnetoresistive effect element 110, in addition to the determined current value. The current modification circuit 130 may be, for example, a one-shot circuit that momentarily increases or decreases the current value, or a multivibrator circuit that can change the current value in a pulse wave or sinusoidal wave form. The current modification circuit 130 may be integrated into the constant voltage source. In this case, the current modification circuit 130 may be implemented as part of the circuit elements constituting the constant voltage source.

[0019] The current change circuit 130 forcibly changes the current value of the current flowing through the magnetoresistive effect elements 110 in response to a control command from the control module 150. The current change circuit 130 may be provided so as to change the current values ​​of the two magnetoresistive effect elements 110 simultaneously as shown in the figure, or may be provided individually for each of the two magnetoresistive effect elements 110. The significance and timing of changing the current value of the magnetoresistive effect elements 110 will be described in detail later.

[0020] The amplifier circuit 140 is a circuit that amplifies the voltage value at the connection point of the two magnetoresistance effect elements 110 and transmits the amplified voltage value to the control module 150, and includes, for example, an operational amplifier. The control module 150 functions as a control unit that controls the magnetic sensor 100, and may be configured to include, for example, a processor (CPU: Central Processing Unit) that executes programs and a memory that stores programs, various parameters, and the like. The control module 150 may be configured to cooperate with a processing chip such as an ASIC (Application Specific Integrated Circuit) or a GPU (Graphics Processing Unit). The control module 150 may be implemented as an SoC (System on Chip) that incorporates processing for controlling the magnetic sensor 100.

[0021] The control module 150 reads out a control program stored in the memory and executes various processes related to the magnetic sensor 100. In particular, as described above, the control module 150 issues control commands to the current changing circuit 130 and calculates the strength of the external magnetic field using the output signal received from the amplifier circuit 140. The control module 150 may be connected to another computer or the like via a network, for example, and may control the magnetic sensor 100 according to commands from the other computer. The magnetic sensor 100 may be configured, for example, housed in a single package, and may be configured by a detection unit including two magnetoresistance effect elements 110, and a processing unit including the current changing circuit 130, the amplifier circuit 140, and the control module 150.

[0022] 2A and 2B are diagrams showing the variation of the vortex configuration of free magnetization 220 with respect to changes in the external magnetic field Hx in a hypothetical magnetoresistive element with no defects in the free layer 112'. Figure 2A shows the vortex configuration when Hx = 0, i.e., when there is no external magnetic field. In the absence of an external magnetic field, a core 221 indicated by a black dot exists near the center of the cross section of the free layer 112', and the free magnetization 220 indicated by the dotted arrow forms a roughly concentric vortex with the core 221 at the center.

[0023] FIG. 2B shows the vortex structure when an external magnetic field is applied in a direction perpendicular to the central axis of the free layer 112′ (the direction of the hollow arrow). When an external magnetic field is applied in the direction of the hollow arrow from the state shown in FIG. 2A (assuming Hx<0), the core 221 moves in the direction indicated by the bold arrow, which is the cross-sectional direction of the free layer 112′ and perpendicular to the external magnetic field. When the core 221 moves in this manner, the vortex structure of the free magnetization 220 is no longer concentric with the core 221. Instead, the free magnetization 220 is relatively small on the side closer to the peripheral edge of the free layer 112′ and relatively large on the side closer to the peripheral edge. Therefore, in the illustrated example, the free magnetization 220 with a component in the same direction as the external magnetic field is greater than the free magnetization 220 with a component opposite to the external magnetic field. In this case, if the direction of the fixed magnetization 210 is the same as the direction of the external magnetic field, the resistance value of the magnetoresistive element is small. Conversely, if the direction of the fixed magnetization 210 is opposite to the direction of the external magnetic field, the resistance value of the magnetoresistive element increases.

[0024] FIG. 2C shows the vortex configuration when an external magnetic field is applied in a direction perpendicular to the central axis of the free layer 112′, opposite to that shown in FIG. 2B (the direction of the hollow arrow). When an external magnetic field is applied in the direction of the hollow arrow from the state shown in FIG. 2A (assuming Hx>0), the core 221 moves in the direction indicated by the bold arrow, which is the cross-sectional direction of the free layer 112′ and perpendicular to the external magnetic field. When the core 221 moves in this manner, the vortex configuration of the free magnetization 220 is no longer concentric with the core 221. Instead, the free magnetization 220 is relatively small on the side where the distance to the peripheral edge of the free layer 112′ is shorter, and relatively large on the side where the distance is longer. Therefore, in the illustrated example, the free magnetization 220 with a component in the same direction as the external magnetic field is greater than the free magnetization 220 with a component in the opposite direction to the external magnetic field. At this time, if the direction of the fixed magnetization 210 is opposite to the direction of the external magnetic field, the resistance value of the magnetoresistive element increases. Conversely, if the direction of the fixed magnetization 210 is the same as the direction of the external magnetic field, the resistance value of the magnetoresistive element decreases.

[0025] Fig. 3 is a diagram showing the magnetization curve of the free layer of the hypothetical magnetoresistive element described in Fig. 2. The horizontal axis represents the external magnetic field Hx, and the vertical axis represents the normalized magnetization Mx of the component along the detection axis direction of the free magnetization 220.

[0026] As shown in the figure, the magnetization curve shows that the magnetization increases with increasing external magnetic field until the external magnetic field reaches Ha, after which the vortex structure disappears and the magnetization reaches a positive saturated state. As the external magnetic field gradually decreases from that state, the magnetization remains saturated for a while, and when the magnetic field decreases to the core-generation magnetic field Hn, the core is regenerated, the vortex structure is restored, and the magnetization instantly decreases to a value almost equal to the value when the external magnetic field was increased. As the external magnetic field decreases further, the magnetization decreases along almost the same path as when the external magnetic field was increased, but in the opposite direction.

[0027] As the external magnetic field decreases further, the magnetization decreases accordingly until it reaches -Ha, at which point the vortex structure disappears and the magnetization reaches a negative saturated state. As the external magnetic field gradually increases from that state, the magnetization remains saturated for a while, and when it increases to the core-generating magnetic field -Hn, the core is regenerated, the vortex structure is restored, and the magnetization instantly increases to a value nearly equal to the value it had when the external magnetic field was decreased. After that, the magnetization increases in the opposite direction, following nearly the same path as when the external magnetic field was decreased.

[0028] As shown by the shaded area in the figure, the magnetization curve has small hysteresis in the magnetization component value with respect to the increase and decrease of the external magnetic field between -Hn and Hn, where the free magnetization 220 forms a vortex, and also has good linearity. Therefore, if this linear region is used as the detection region for the external magnetic field, a magnetic sensor can be realized that achieves both high linearity and reproducibility of the hysteresis loop with respect to changes in the external magnetic field.

[0029] However, the actual free layer 112 may contain random defects in the material, and these defects may hinder the fluctuation of the core 221 in response to changes in the external magnetic field. Figure 4 is a diagram showing an example of the fluctuation of the core 221 in response to changes in the external magnetic field in a realistic magnetoresistive element 110. Specifically, the thick arrows are used to schematically show how the core 221 fluctuates as the external magnetic field gradually increases from a state of 0 (Hx>0).

[0030] The white circles represent typical defects 290 present in the material of the free layer 112. If the defects 290 were not present, the core 221 would fluctuate approximately linearly, as indicated by the dotted arrow. However, due to the presence of defects 290 in the path of the fluctuating core 221, the core 221 may be trapped by the defects 290. The core 221 trapped by the defects does not fluctuate in response to a slight increase or decrease in the external magnetic field. In other words, the vortex configuration of the free magnetization 220 does not change during that time. After that, when the external magnetic field increases or decreases beyond a certain range, the core 221 escapes the defects 290 and fluctuates again.

[0031] 5 is a diagram showing an example of a realistic magnetization curve in the linear region of the magnetoresistive effect element 110 when the current change circuit 130 according to this embodiment is not operated. Specifically, the thick line shows the magnetization curve when the core 221 is captured by different defects 290 when the external magnetic fields are H1 and H2, and the dotted line shows the magnetization curve when the defect 290 does not exist.

[0032] When the core 221 is trapped by the defect 290, the core position of the free magnetization 220 does not change for a while, even if the external magnetic field increases, as described above. Therefore, the magnetization Mx remains approximately constant during this time. When the external magnetic field increases beyond a certain range, the core 221 leaves the defect 290 and begins to fluctuate again. However, this hysteresis is observed until the core 221 leaves the defect 290. This hysteresis deteriorates the output reproducibility of the magnetic sensor. When the core is trapped by the defect 290, the magnetization Mx does not change or changes less than it should, even though the external magnetic field is increasing. Therefore, the resistance value of the magnetoresistive element 110 also does not change as it should. In this case, errors may occur in the measurement results of the external magnetic field. Therefore, the magnetic sensor 100 of this embodiment uses the current change circuit 130 to reduce hysteresis caused by the defect 290 and improve the reproducibility of the hysteresis loop.

[0033] 6 is a diagram showing an example of a magnetization curve in the linear region of the magnetoresistive effect element 110 when the current change circuit 130 according to this embodiment is operated. In this embodiment, as will be described later, the current change circuit 130 is operated, for example, periodically to forcibly change the current value of the current flowing through the magnetoresistive effect element 110. The current change circuit 130 is configured to change the current value of the current flowing through the magnetoresistive effect element 110 by controlling the supply voltage V SUP By applying a voltage value different from the voltage value to the magnetoresistive element 110, the value of the current flowing through the magnetoresistive element 110 is forcibly increased or decreased.

[0034] When the current value flowing through the magnetoresistive element 110 increases or decreases, the current magnetic field (e.g., magnetic field B indicated by the solid arrow in the figure) caused by the increasing or decreasing current changes the vortex shape of the free layer magnetization, causing the core 221 to quickly escape the defect 290 and return to its original magnetization curve. The illustrated example shows the core 221 being captured by the defect 290 when the external magnetic field is H1 and H2, and then a current pulse CP is applied by the current change circuit 130 at a later timing. After the current pulse CP is applied, the core 221 returns to the magnetization curve it would have had if the defect 290 were not present. For example, applying a current pulse before measuring the external magnetic field can reduce hysteresis in the output voltage and improve the reproducibility of the hysteresis loop.

[0035] 7 is a diagram showing the change over time in the value of the current flowing through the magnetoresistive element 110 when the external magnetic field is constant, where the horizontal axis represents the passage of time and the vertical axis represents the current value.

[0036] Since the magnetic sensor 100 in this embodiment is a sensor that detects an external magnetic field, the control module 150 amplifies the voltage value at the connection point of the two magnetoresistance effect elements 110 using the amplifier circuit 140, for example, periodically or at any timing, to detect the magnitude of the external magnetic field. During the detection period Td (the shaded portion in the figure) for detecting the magnitude of the external magnetic field, the supply voltage V SUP Since the control module 150 detects the partial voltage of the two magnetoresistance effect elements 110 when the current is supplied, the control module 150 does not operate the current changing circuit 130.

[0037] The control module 150 operates the current change circuit 130 during a non-detection period Tn other than the detection period Td of the external magnetic field. The figure shows a state in which the current change circuit 130 is operated during a certain non-detection period Tn to pass a current pulse CP through the magnetoresistive effect element 110.

[0038] When the control module 150 periodically operates the current change circuit 130, it is preferable that the control module 150 allocates at least the period of the operation to the non-detection period Tn and controls the operation so as not to overlap with the detection period Td. When the detection period Td overlaps with the period in which the current change circuit 130 is operated and priority is given to the detection of the external magnetic field, the control module 150 may adjust the operation of the current change circuit 130 to be skipped.

[0039] Furthermore, since the magnetic sensor 100 in this embodiment is intended to detect an external magnetic field within the linear region described with reference to FIG. 3 , the control module 150 operates the current change circuit 130 between −Hn and Hn, where the free magnetization 220 forms a vortex. Therefore, the control module 150 may start controlling the current change circuit 130 to change the current value when it detects the timing at which the magnitude of the external magnetic field gradually decreases from a state greater than Hn and the core is reformed, or the timing at which the magnitude of the external magnetic field gradually increases from a state smaller than −Hn and the core is reformed, or −Hn, where the magnitude of the external magnetic field gradually increases from a state smaller than −Hn and the core is reformed. At the timing of the core-generating magnetic field Hn or −Hn, whether the rotation direction of the vortex formed in the free magnetization 220 is clockwise or counterclockwise is determined randomly unless there is a particular external influence. In contrast, the magnetic sensor 100 can guide the rotation direction of the vortex formed in the free magnetization 220 to be determined in either of the intended directions by controlling the direction of the current flowing through the current change circuit 130 at this timing. That is, as described above, the current magnetic field generated by the current flowing from the current change circuit 130 is generated clockwise or counterclockwise in the free layer 112, and therefore, by controlling the direction of the current when the vortex is formed, it is possible to induce the rotation direction of the vortex of the formed free magnetization 220 to be determined in the intended direction. By increasing the reproducibility of the rotation direction of the vortex, it is possible to further improve the reproducibility of the hysteresis loop.

[0040] The amount by which the current value of the magnetoresistive element 110 is increased or decreased by the current change circuit 130 can be determined based on the characteristics of the free layer 112 and the direction and magnitude of the external magnetic field at that time, as long as it ultimately changes the position of the core 221. For example, when the external magnetic field is strong, the control module 150 may limit the current value to a level that does not cause the core 221 to disappear. Alternatively, the control module 150 may control the current value to instantaneously increase when the external magnetic field is gradually increasing, and instantaneously decrease when the external magnetic field is gradually decreasing. The control module 150 may increase or decrease the current value of the magnetoresistive element 110 at least once when changing the position of the core 221, but may also increase or decrease the current value continuously to limit the fluctuation range of the current value per increase or decrease. In this case, the current value may be increased or decreased using a pulse wave or a sine wave. In order to effectively vary the position of the core 221, the control module 150 may control the current changing circuit 130 to apply a one-shot pulse wave that causes a current of an appropriate magnitude to flow.

[0041] Furthermore, when a magnetoresistive effect element 110 whose resistance value changes not only with an external magnetic field but also with temperature is employed, the control module 150 may measure the temperature of the magnetoresistive effect element 110 and adjust the current value to be varied in accordance with the temperature. In this case, a temperature detection sensor is disposed near the magnetoresistive effect element 110, and the control module 150 operates the current change circuit 130 in accordance with the detection result of the temperature detection sensor. Furthermore, for example, the control module 150 may estimate the temperature of the magnetoresistive effect element 110 from the resistance value of the magnetoresistive effect element 110 based on a preset relationship between the temperature of the magnetoresistive effect element 110 and its resistance value, and adjust the current value based on the estimated temperature.

[0042] Next, we will summarize the series of processing steps executed by the control module 150. Figure 8 is a flow diagram of the control processing executed by the control module. The flow starts in response to a command to start the processing for detecting an external magnetic field.

[0043] In step S101, the control module 150 checks whether the current timing is a detection period for detecting an external magnetic field. If it is a detection period, the process proceeds to step S102. If it is not a detection period, the process proceeds to step S103, assuming that it is a non-detection time. If the process proceeds to step S102, the control module 150 executes an external magnetic field detection process. Specifically, the control module 150 acquires the voltage value output by the amplifier circuit 140, converts it into a digital value, for example, and transmits it to an external management device. Then, the process proceeds to step S105.

[0044] When the process proceeds from step S101 to step S103, the control module 150 checks whether it is time to change the current value. If it is time to change the current value, the process proceeds to step S104, where the current change circuit 130 is operated to change the value of the current flowing through the magnetic sensor 100. When the process of changing the current value in step S104 is completed, or when it is confirmed in step S103 that it is not time to change the current value, the process proceeds to step S105.

[0045] When the control module 150 proceeds to step S105, it checks whether or not a control-off command has been received from the user or an external device. If a control-off command has not been received, the control module 150 returns to step S101 and repeats the series of processes. If a control-off command has been received, the series of processes is terminated.

[0046] Next, a modified example of the above disclosure will be described. Fig. 9 is a conceptual diagram showing the overall configuration of a magnetic sensor 100' according to a modified example of the present disclosure. The magnetic sensor 100' differs from the above magnetic sensor 100 in that it includes a switch 131, and the control module 150 also controls the switch 131. Components similar to those of the magnetic sensor 100 are given the same reference numerals, and descriptions thereof will be omitted unless otherwise noted.

[0047] The switch 131 connects the magnetoresistive element 110 to the supply voltage V SUP, the current changing circuit 130, or neither, and is configured by, for example, a semiconductor switch. The control module 150' controls the magnetoresistive effect element 110 to supply voltage V SUP 1. At the timing when the current changing circuit 130 is operated, a switch signal is sent to the switch 131 so that the magnetoresistive effect element 110 is connected to the current changing circuit 130. At other times, the magnetoresistive effect element 110 is kept connected to neither.

[0048] 10 is a diagram showing a change over time in the value of the current flowing through the magnetoresistive effect element 110 according to the modified example. As described above, the control module 150 applies the supply voltage V SUP Therefore, even during the detection period Td, the switch 131 is connected to the supply voltage V SUP Similarly, the control module 150 connects the magnetoresistive element 110 to the current changing circuit 130 at the timing when the current is to flow from the current changing circuit 130 to the magnetoresistive element 110. Therefore, even during the non-detection period Tn, the switch 131 is disconnected from the supply voltage V SUP and the current change circuit 130, so that power consumption can be reduced.

[0049] The control module 150 may control the current change circuit 130 to operate only at the timing when a current is passed through the magnetoresistive effect element 110. That is, the control may be such that the current change circuit 130 operates in synchronization with the timing when the switch 131 is connected to the current change circuit 130. Alternatively, instead of the control module 150 directly controlling the current change circuit 130, the control module 150 may operate the current change circuit 130 to pass a current through the magnetoresistive effect element 110 when the switch 131 is connected, and the control module 150 may control the switch 131 to cause the current change circuit 130 to change the value of the current passing through the magnetoresistive effect element 110. The switch 131 may also be configured to connect the magnetoresistive effect element 110 to the supply voltage V SUP Alternatively, the switch 131 may be a toggle switch that connects the switch 131 to the current changing circuit 130 or to the current changing circuit 130. In this case, power consumption can be reduced by connecting the switch 131 to the current changing circuit 130 and controlling the current changing circuit 130 to an inactive state.

[0050] Although the magnetic sensor 100 according to this embodiment has been described above, the magnetic sensor 100 may be modified in various other ways. For example, in the above example, two magnetoresistive effect elements 110 are connected in series to form a half-bridge circuit for detecting an external magnetic field. However, the circuit configuration is not limited to this. For example, a full-bridge circuit may be formed using four magnetoresistive effect elements 110. Furthermore, the magnetic sensor 100 may be formed by connecting one or more magnetoresistive effect elements 110 using a circuit configuration other than a bridge circuit. However, when forming a circuit including multiple magnetoresistive effect elements 110, it is preferable that the current direction is the same for all of the magnetoresistive effect elements 110. In other words, it is preferable that the magnetic field caused by the current change by the current change circuit 130 is uniformly affected. [Explanation of symbols]

[0051] 100, 100'...magnetic sensor, 110...magnetoresistive element, 111...fixed layer, 112, 112'...free layer, 113...non-magnetic layer, 114...lead electrode, 130...current changing circuit, 131...switch, 140...amplifying circuit, 150...control module, 210...fixed magnetization, 220...free magnetization, 221...core, 290...defect

Claims

1. a magnetoresistive element connected between a power supply and a ground, the magnetoresistive element having a fixed layer with fixed magnetization, a free layer with free magnetization that forms a vortex configuration in the absence of an external magnetic field, and a non-magnetic layer provided between the fixed layer and the free layer; a current changing circuit that changes the current value of the current flowing through the magnetoresistive element; A magnetic sensor comprising:

2. The magnetic sensor according to claim 1 , further comprising a control section that causes the current change circuit to change the current value during a non-detection period that is not a detection period in which an external magnetic field is detected.

3. The magnetic sensor according to claim 2 , wherein the control unit causes the current changing circuit to change the current value so as to vary the position of the core of the vortex structure.

4. The magnetic sensor according to claim 2 , wherein the control unit causes the current changing circuit to change the current value at least once at any timing during the non-detection period.

5. The magnetic sensor according to claim 4 , wherein the control unit causes the current changing circuit to repeatedly increase and decrease the current value continuously.

6. 4. The magnetic sensor according to claim 3, wherein the control unit starts the non-detection period when it detects a timing at which the core is reformed in response to a change in an external magnetic field during the detection period, and causes the current change circuit to change the current value.

7. The magnetic sensor according to claim 2 , wherein the control unit causes the current change circuit to change the current value based on the direction and magnitude of the external magnetic field detected during the detection period.

8. The magnetic sensor according to claim 2 , wherein the control unit causes the current changing circuit to change the current value based on the temperature of the magnetoresistive element.

9. 2. The magnetic sensor according to claim 1, wherein the magnetoresistive element has a columnar lead electrode directly connected to an end face of the free layer and having a contact surface smaller in area than the end face.

10. 2. The magnetic sensor according to claim 1, wherein when a plurality of the magnetoresistive effect elements are provided, the magnetoresistive effect elements are wired so that the current direction is the same for all of the magnetoresistive effect elements.

11. a detection step of causing a magnetoresistive element connected between a power source and ground, the magnetoresistive element having a fixed layer with fixed magnetization, a free layer with free magnetization that forms a vortex configuration in the absence of an external magnetic field, and a non-magnetic layer provided between the fixed layer and the free layer, to detect an external magnetic field without causing a current change circuit capable of changing the current value of a current flowing through the magnetoresistive element to change the current value; a changing step of causing the current changing circuit to change the current value during a non-detection period in which the external magnetic field is not detected; A method for controlling a magnetic sensor having the above structure.

12. The method for controlling a magnetic sensor according to claim 11 , wherein the changing step causes the current changing circuit to change the current value so as to vary the position of the core of the vortex configuration.

13. a detection step of causing a magnetoresistive element connected between a power source and ground, the magnetoresistive element having a fixed layer with fixed magnetization, a free layer with free magnetization that forms a vortex configuration in the absence of an external magnetic field, and a non-magnetic layer provided between the fixed layer and the free layer, to detect an external magnetic field without causing a current change circuit capable of changing the current value of a current flowing through the magnetoresistive element to change the current value; a changing step of causing the current changing circuit to change the current value during a non-detection period in which the external magnetic field is not detected; A magnetic sensor control program that causes a computer to execute the above.

14. The magnetic sensor control program according to claim 13 , wherein the changing step causes the current changing circuit to change the current value so as to vary a position of a core of the vortex configuration.

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