Magnetic sensor element, magnetic sensor device, magnetic sensor system, and method for manufacturing magnetic sensor element

Abstract

A magnetic sensor element (100) for measuring a magnetic field comprises: a substrate (10); a heavy metal layer (12) which is stacked on the substrate (10); an antiferromagnetic layer (14) which is stacked on the heavy metal layer (12) and which comprises a first antiferromagnetic material (for example, Mn3Sn) that has an antiferromagnetic magnetic structure having macroscopically broken time reversal symmetry; and a cap layer (16) which is stacked on the antiferromagnetic layer (14). In the heavy metal layer (12), when a current (I) flows in an in-plane direction, a spin current is generated in a direction perpendicular to the plane, and a spin-orbit torque generated by the spin current acts on the magnetic order of the first antiferromagnetic material of the antiferromagnetic layer (14), thereby controlling the magnetic order. The first antiferromagnetic material of the antiferromagnetic layer (14) has a read signal that responds linearly to a magnetic field within a predetermined magnetic field range including zero magnetic field.

Description

Magnetic sensor element, magnetic sensor device, magnetic sensor system, and method for manufacturing magnetic sensor element

[0001] The present invention relates to a magnetic sensor element, a magnetic sensor device, a magnetic sensor system, and a method for manufacturing a magnetic sensor element.

[0002] Hall sensors, a type of magnetic sensor, measure magnetic fields using the Hall effect. The Hall effect is a phenomenon in which, when a magnetic field is applied perpendicular to a current, a voltage (Hall voltage) is generated in a direction perpendicular to both the current and the magnetic field. Because this Hall voltage is proportional to the strength and direction of the magnetic field, Hall sensors are effective for measuring magnetic fields (see, for example, Patent Document 1). Tunneling magnetoresistance (TMR) sensors, which utilize the TMR effect, in which resistance changes with a magnetic field, are also widely known (see, for example, Patent Document 2).

[0003] JP 2020-13891 A International Publication No. 2020 / 208907

[0004] In recent years, there has been a demand for magnetic sensors with high sensitivity and excellent response characteristics in a variety of applications, including portable devices, automobiles, and medical equipment.

[0005] An object of the present invention is to provide a magnetic sensor element, a magnetic sensor device, a magnetic sensor system, and a method for manufacturing a magnetic sensor element that have excellent response characteristics using an antiferromagnetic material with negligibly small leakage magnetic field.

[0006] The magnetic sensor element according to the present invention is a magnetic sensor element for measuring a magnetic field, and comprises an antiferromagnetic layer which comprises a first antiferromagnetic material having an antiferromagnetic magnetic structure in which time-reversal symmetry is macroscopically broken, and in which a readout signal responds linearly to a magnetic field within a predetermined magnetic field range including zero magnetic field.

[0007] A magnetic sensor device according to the present invention includes the above-described magnetic sensor element, a current supply unit that supplies a current to the magnetic sensor element, and a processor that processes a read signal from the antiferromagnetic layer of the magnetic sensor element.

[0008] A magnetic sensor system according to the present invention is a magnetic sensor system in which a plurality of magnetic sensor elements are arranged, and each of the plurality of magnetic sensor elements is defined as the magnetic sensor element described above.

[0009] The method for manufacturing a magnetic sensor element according to the present invention includes forming a multilayer film having at least a substrate made of an insulator, a cap layer made of an oxide, and an antiferromagnetic layer provided between the substrate and the cap layer, and after forming the multilayer film, annealing the multilayer film.

[0010] According to the present invention, by using an antiferromagnetic layer made of a first antiferromagnetic material having an antiferromagnetic magnetic structure in which time-reversal symmetry is macroscopically broken, a magnetic sensor element having excellent response characteristics can be provided, in which the readout signal responds linearly to the magnetic field within a predetermined magnetic field range including zero magnetic field.

[0011] 1 is a cross-sectional view of a magnetic sensor element according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view of a magnetic sensor element according to a modified example of the first embodiment; ３ 1 is a graph showing the X-ray diffraction pattern of a Sn / MgO sample. ３ 1 is a schematic diagram for explaining current-induced magnetic rotation (chiral spin rotation) of Sn; FIG. 2 is a schematic diagram showing the configuration of a magnetic sensor element with a Hall bar structure; FIG. 3 is a block diagram of a magnetic sensor device including the magnetic sensor element; ３ 1 is a graph showing the perpendicular magnetic field dependence of the Hall resistivity of Sn at 300 K when a current exceeding the threshold current of current-induced magnetic rotation (chiral spin rotation) is applied to the heavy metal layer in the magnetic sensor element of the first embodiment. ３ 1 is a graph showing the perpendicular magnetic field dependence of the Hall resistivity of Sn; FIG. 2 is a schematic diagram of a hysteresis loop for explaining the control of magnetic permeability by current; FIG. 3 is a cross-sectional view of a magnetic sensor element according to a second embodiment of the present invention; FIG. 4 is a cross-sectional view of a magnetic sensor element according to a modified example of the second embodiment; and FIG. 5 is a graph showing the perpendicular magnetic field dependence of the Hall resistivity of Sn. ３ 10 is a graph showing the perpendicular magnetic field dependence of the Hall resistivity of Sn. ３Mn at 300 K when the antiferromagnetic order of Sn is reversed ３ 8B is a cross-sectional view of a magnetic sensor element having a configuration in which the heavy metal layer is removed from the magnetic sensor element of FIG. 8A; FIG. 8C is a cross-sectional view of a magnetic sensor element having a configuration in which the heavy metal layer is removed from the magnetic sensor element of FIG. 8B; FIG. 8D is a cross-sectional view of a magnetic sensor element having an antiferromagnetic layer that is a granular layer; FIG. 8E is a cross-sectional view of a magnetic sensor element having an antiferromagnetic layer that is a single crystal film or an epitaxial film; FIG. 8F is a cross-sectional view of a magnetic sensor element according to a third embodiment of the present invention; FIG. 8G is a graph showing the perpendicular magnetic field dependence of the Hall resistivity of Sn; FIG. 8H is a timing chart showing the timing relationship between the current applied to the magnetic sensor element and the readout signal from the magnetic sensor element; FIG. 8H is a cross-sectional view of a magnetic sensor element having a configuration in which the heavy metal layer is removed from the magnetic sensor element of FIG. 8A; ３ 1 is a graph showing the perpendicular magnetic field dependence of the Hall resistivity of Sn. FIG. 2 is a schematic diagram showing the configuration of a magnetic sensor system including a plurality of magnetic sensor elements.

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or similar components are designated by the same reference numerals throughout the drawings. The drawings are schematic, and the relationship between planar dimensions and thickness, and the thickness ratio of each component, differ from the actual ones. Furthermore, it goes without saying that the dimensional relationships and ratios of each component differ between the drawings.

[0013] In the following embodiments, a multilayer film may be expressed by the material of each layer that constitutes the multilayer film. For example, if a layer of material b and a layer of material c are stacked in this order on a layer of material a, the multilayer film will be expressed as "material a / material b / material c." The thickness (nm) of each layer may be written in parentheses after the name of the material. For example, a layer having a thickness of ti (nm) and made of material j will be expressed as "material j (ti)."

[0014] First Embodiment A first embodiment of the present invention will be described with reference to Figures 1A to 7. The magnetic sensor element of the first embodiment controls the coercive force or magnetic permeability by a current.

[0015] 1A, the magnetic sensor element 100 of the first embodiment includes a substrate 10, a heavy metal layer 12 stacked on the substrate 10, an antiferromagnetic layer 14 as a magnetosensitive layer stacked on the heavy metal layer 12, and a cap layer 16 stacked on the antiferromagnetic layer 14. Alternatively, as shown in FIG. 1B, a magnetic sensor element 102 (substrate / antiferromagnetic layer / heavy metal layer / cap layer) in which the heavy metal layer 12 is stacked on the antiferromagnetic layer 14 may be employed.

[0016] The substrate 10 is made of MgO, SiO ２ The heavy metal layer 12 is made of a non-magnetic heavy metal such as tantalum (Ta), tungsten (W), or platinum (Pt).

[0017] The antiferromagnetic layer 14 is composed of an antiferromagnetic material (first antiferromagnetic material) having an antiferromagnetic magnetic structure in which time reversal symmetry is broken macroscopically. Such first antiferromagnetic materials include non-collinear antiferromagnetic materials and alternating magnetic materials. The first antiferromagnetic material of the antiferromagnetic layer 14 can exhibit the anomalous Hall effect based on the antiferromagnetic magnetic structure in which time reversal symmetry is broken macroscopically. The first antiferromagnetic material also includes antiferromagnetic metals containing manganese (Mn) and collinear antiferromagnetic materials having a rutile-type crystal structure. Examples of the former include Mn ３ X (X is one or more selected from the group consisting of Sn, Ge, Ga, Rh, Pt, and Ir), Mn ３ XN (X is one or more selected from the group including Ga, Sn, and Ni). An example of the latter is RuO ２ and Mn ５ Si ３ , CrSb. As long as the antiferromagnetic magnetic structure with macroscopically broken time-reversal symmetry is compensated, non-stoichiometric compounds with misaligned composition ratios and compounds containing contaminants are also acceptable. By adjusting the composition ratio of the compounds, the temperature range and sensitivity of magnetic field measurement can be adjusted.

[0018] The cap layer 16 is provided to prevent oxidation and is made of an oxide such as MgO or AlOx. Note that the magnetic sensor element 100 can function as a magnetic sensor even without the cap layer 16. The same applies to the second and third embodiments described below.

[0019] When a current I is passed through the heavy metal layer 12 in the in-plane direction, a spin current is generated in the perpendicular direction due to the spin Hall effect, and the spin-orbit torque (SOT) generated by the spin current acts on the magnetic order of the antiferromagnetic layer 14 in contact with the heavy metal layer 12, thereby controlling the magnetic order.

[0020] Next, an example of a method for manufacturing the magnetic sensor element 100 will be described. ３ An example is given in which a Sn (15 nm) / MgO (5 nm) multilayer film is formed. Note that the thickness (nm) of each layer of the magnetic sensor element 100 is an example and is not limited thereto.

[0021] First, the MgO substrate is annealed in an ultra-high vacuum chamber at 800°C for 10 minutes. ３ The Sn (15 nm) / MgO (5 nm) multilayer film has a base pressure of 2 × 10 －８ The MnO (110) substrate was fabricated by molecular beam epitaxy (MBE) under ultra-high vacuum of 100 Pa. A W (10 nm) layer was deposited at a rate of 0.1 Å / s at 300 °C and then annealed at 800 °C for 10 min. ３ The Sn (15 nm) layer is prepared by co-evaporation of Mn and Sn at a rate of 0.25 Å / s. ３ A layer of Sn (5 nm) is deposited at room temperature and then annealed at 400° C. Then, additional Mn ３ A layer of Sn (10 nm) is deposited at about 260°C.

[0022] Then, a MgO layer (5 nm) is grown at room temperature at a rate of 0.1 Å / s. Finally, the MgO (110) substrate / W ​​(10 nm) / Mn ３ The Sn (15 nm) / MgO (5 nm) multilayer film is annealed at 700° C. for 30 minutes.

[0023] In this way, by annealing the multilayer film after laminating the MgO layer as the cap layer 16 (cap annealing), the Mn ３ The coercive force of the Sn layer can be reduced.

[0024] As a result of composition analysis by SEM-EDX, Mn ３ The composition of the Sn layer is Mn ３．０５ Sn ０．９５ Figure 2 shows the MgO (110) substrate / W ​​(10 nm) / Mn ３ The X-ray diffraction pattern of the Sn (15 nm) / MgO (5 nm) sample is shown in Figure 2. As shown in Figure 2, the W layer is (211) oriented, and the Mn ３ It was found that the Sn layer was an epitaxial film with a (01-10) orientation.

[0025] Furthermore, by measuring with a four-terminal method, it was found that the bilayer W (10 nm) / Mn ３ The resistivity of Sn (15 nm) was 136 μΩcm. The resistivity of W is known to be 40 μΩcm from measurements of a single layer film. ３ The resistivity of Sn is determined to be 200 μΩcm.

[0026] As shown in FIG. ３ Sn is an antiferromagnetic material with a triangular crystal structure called the kagome lattice, with the kagome lattice stacked in the

[0001] direction. Due to geometric frustration, Mn atoms located at the vertices of the kagome lattice exhibit a non-collinear magnetic structure at temperatures below 420 K, in which the magnetic moments (localized spin orientations) are inclined 120 degrees relative to each other. Three types of six-spin units arranged on a two-layer kagome lattice form a spin order called a cluster magnetic octupole, represented by a hexagon. This antiferromagnetic magnetic structure macroscopically breaks time-reversal symmetry.

[0027] The Mn of the magnetic sensor element fabricated as described above ３The Sn layer is a single crystal film or an epitaxial film, and has a (2-1-10) or (01-10) orientation, with the kagome plane perpendicular to the film surface. When a predetermined current I is passed through the heavy metal layer 12 in the in-plane direction (x direction), a spin current is generated in the direction perpendicular to the plane (z direction). The SOT generated by the spin current causes the Mn ３ By utilizing this current-induced magnetic rotation (chiral spin rotation), Mn ３ The coercive force of the Sn layer can be suppressed. The suppression of coercive force using current-induced magnetic rotation will be described later (see FIGS. 6A and 6B).

[0028] 4 shows a Hall bar structure when the magnetic sensor element 100 is an element for a Hall sensor (Hall element). In the magnetic sensor element 100 with the Hall bar structure, electrodes 17a and 17b made of Au / Ti are arranged at both ends in the longitudinal direction (x direction), and electrodes 18a and 18b made of Au / Ti are arranged in the lateral direction (y direction). Note that the cap layer 16 is omitted in FIG. 4.

[0029] A write current I is applied between the electrodes 17a and 17b. write or read current I read flows, and a Hall voltage V Ｈ is detected.

[0030] A write current I write When a current (e.g., a pulse current, an AC current, etc.) is passed in the longitudinal direction (x direction), a spin current is generated in the direction perpendicular to the surface (z direction) due to the spin Hall effect, and the SOT generated by the spin current acts on the magnetic order of the antiferromagnetic layer 14, thereby controlling the magnetic order.

[0031] When measuring a magnetic field, a read current I read (direct current) flows in the x direction. This generates a Hall voltage V according to the magnitude of the magnetic field due to the anomalous Hall effect. Ｈ occurs.

[0032] 5 shows the configuration of a magnetic sensor device 1000 including the magnetic sensor element 100. The magnetic sensor device 1000 includes the magnetic sensor element 100, a current supply unit 1002, a processor 1004, a memory 1006, and a voltage detection unit 1008. The current supply unit 1002 supplies a current (I write , I read The voltage detection unit 1008 reads out a signal (Hall voltage V Ｈ The processor 1004 has a central processing unit (CPU), controls the current supply unit 1002 to supply current to the magnetic sensor element 100, and detects the read signal (Hall voltage V Ｈ The memory 1006 stores data and read signals required for the processor 1004 to execute various processes.

[0033] The Hall bar structure of FIG. 4 and the magnetic sensor device 1000 of FIG. 5 are applicable not only to the magnetic sensor element 100 of FIG. 1A but also to the magnetic sensor element 102 of FIG. 1B and the magnetic sensor elements of the second and third embodiments described below.

[0034] Next, the results of measuring a magnetic field using the magnetic sensor element 100 as a Hall element will be described. The multilayer film of the magnetic sensor element 100 used for the measurement was a MgO (110) substrate / W ​​(10 nm) / Mn ３ A Sn (15 nm) / MgO (5 nm) Hall bar measuring 2 μm wide and 12 μm long was fabricated by photolithography.

[0035] In FIG. 6A, a current of 0.4 mA was applied to the entire multilayer film (I write =0.3mA, current density J ｗ = 1.5 MA / cm ２ ) was applied and the signal was read out at a current of 0.4 mA. ３ The Hall resistivity of the Sn layer is dependent on the perpendicular magnetic field. write = 3mA, J ｗ = 15 MA / cm ２) was applied and the signal was read out at a current of 4 mA. ３ 1 shows the perpendicular magnetic field dependence of the Hall resistivity of the Sn layer.

[0036] Comparing FIG. 6A and FIG. 6B, in FIG. 6B, Mn ３ It can be seen that the width in the magnetic field direction of the hysteresis loop representing the response of the Sn layer is almost completely eliminated. That is, Fig. 6B shows the threshold current (current density 1 MA / cm) that causes current-induced magnetic rotation (chiral spin rotation). ２ ~100 MA / cm ２ When a write current exceeding ρ (order of ρ) is applied and the magnetic field is measured, the read signal responds linearly to the magnetic field over a given magnetic field range, including zero magnetic field (see dotted line). Ｈ , and the magnetic field is denoted as B. From FIG. 6B, the gradient dρ Ｈ / dB=-0.0057 (μΩcm / mT). The absolute value of the slope |dρ Ｈ The larger the value of / dB|, the higher the sensitivity. The inherent noise frequency caused by current-induced magnetic rotation (chiral spin rotation) changes in proportion to the current density, but is robust to minute magnetic fields of 0.1 T or less and takes an almost constant value.

[0037] Thus, by a current exceeding the threshold current for current-induced magnetic rotation (chiral spin rotation), Mn ３ The coercivity of the Sn layer can be suppressed to nearly zero, and a Hall voltage can be induced in zero magnetic field. The phenomenon of the Hall voltage changing rapidly as a function of magnetic field indicates that the magnetic sensor element 100 is useful as a magnetic field probe.

[0038] Next, we will explain how to control the magnetic permeability using a current. Controlling the magnetic permeability is useful for creating conditions with and without a magnetic field that the magnetic sensor must measure. The difference in the readout signal between the presence and absence of a magnetic field allows us to remove 1 / f noise and other environmental noise, resulting in a highly accurate signal.

[0039] As an example of the magnetic sensor element 100 capable of controlling the magnetic permeability, a MgO (110) substrate / W / Mn ３An example of the multilayer film is a Sn / MgO multilayer film. ３ The Sn layer is a polycrystalline film or an epitaxial film. ３ When the Sn layer is an epitaxial film, the kagome plane, which is the current-induced gyromagnetic plane, is oriented perpendicular to the substrate.

[0040] Such a magnetic sensor element 100 provides maximum permeability when a magnetic field is applied in the perpendicular direction and a current exceeding the critical current density is supplied. When an in-plane magnetic field is applied, a read signal that is two orders of magnitude smaller than when a perpendicular magnetization is applied is obtained. Here, the critical current density is 10 MA / cm. ２ , 100 MA / cm ２ An order of 100g is recommended.

[0041] When the current is less than the critical current density, the magnetic domains in the antiferromagnetic layer 14 are randomly oriented, and the coercivity is 0.1 T or greater. Therefore, the permeability immediately after the current is reduced below the critical current density is one to two orders of magnitude smaller than when measured under a current exceeding the critical current density. The dotted line in Figure 7 shows the hysteresis loop representing the response to a magnetic field when no current is supplied and the coercivity is greater than 0.1 T. The thick solid line in Figure 7 represents the response to a magnetic field when a current exceeding the critical current density is supplied. The hysteresis loop narrows, indicating that the read signal responds linearly to the magnetic field over a specified magnetic field range, including zero magnetic field.

[0042] To remove background noise using the magnetic sensor element 100, a first current greater than the critical current density and a second current less than the critical current density are alternately supplied to the heavy metal layer 12, and the difference between the resulting read signals is calculated.

[0043] When the current supply unit 1002 supplies a first current to the heavy metal layer 12, the magnetic permeability of the antiferromagnetic layer 14 increases, and the magnetic field to be measured and noise are detected. On the other hand, when the current supply unit 1002 supplies a second current to the heavy metal layer 12, the magnetic permeability of the antiferromagnetic layer 14 decreases, making it difficult to detect the magnetic field and only noise is detected. The processor 1004 calculates a first read signal (Hall resistivity ρ Ｈor Hall voltage V Ｈ ) and a second readout signal (Hall resistivity ρ Ｈ or Hall voltage V Ｈ ) and compare them. For example, the processor 1004 normalizes the first read signal and the second read signal by the magnitude of the current and calculates the difference between the two signals. This makes it possible to remove background noise. Furthermore, by controlling the magnetic permeability of the antiferromagnetic layer 14, the magnitude of the magnetic field applied to the magnetic sensor portion can be changed, thereby providing a highly sensitive magnetic sensor.

[0044] 8A to 13, a second embodiment of the present invention will be described. The magnetic sensor element of the second embodiment includes an antiferromagnetic material in the antiferromagnetic layer and a bias layer that generates an exchange bias. Like the antiferromagnetic layer of the first embodiment, the antiferromagnetic layer of the second embodiment is also made of a first antiferromagnetic material having an antiferromagnetic magnetic structure in which time-reversal symmetry is broken macroscopically.

[0045] 8A, the magnetic sensor element 200 of the second embodiment includes a substrate 10, a heavy metal layer 12 stacked on the substrate 10, an antiferromagnetic layer 14 stacked on the heavy metal layer 12, a bias layer 28 stacked on the antiferromagnetic layer 14, and a cap layer 26 stacked on the bias layer 28. Alternatively, as shown in Fig. 8B, a magnetic sensor element 202 (substrate / bias layer / antiferromagnetic layer / heavy metal layer / cap layer) may be employed in which the stacking positions of the heavy metal layer 12 and the bias layer 28 are interchanged.

[0046] The bias layer 28 is made of an antiferromagnetic material (second antiferromagnetic material) such as Mn—Pt, Mn—Ir, Mn—N, NiO, CoO, etc. When the bias layer 28 is in contact with the antiferromagnetic layer 14, a magnetic coupling effect called exchange bias occurs at the interface between the two layers.

[0047] Next, an example of a method for manufacturing the magnetic sensor element 200 will be described. ３An example is shown in which a multilayer film of Sn (15 nm) / MnPt (15 nm) / AlOx (5 nm) is formed. Note that the thickness (nm) of each layer of the magnetic sensor element 200 is an example and is not limited thereto.

[0048] First, an example of the magnetic sensor element 100 of the first embodiment is a MgO (110) substrate / W ​​(10 nm) / Mn ３ A Sn (15 nm) / MgO (5 nm) multilayer film is fabricated by the above-mentioned method. Next, the MgO (5 nm) layer is removed by dry etching using argon (Ar) ion milling. Then, the Mn ３ MnPt is deposited to a thickness of 15 nm on the top surface of the Sn (15 nm) layer by sputtering, and then AlOx is deposited to a thickness of 5 nm by sputtering at room temperature.

[0049] In addition, the MgO (110) substrate / W / Mn ３ When a manufacturing method is adopted in which the Sn / MnPt / AlOx multilayer film is formed in order from the bottom layer, Mn ３ The Sn layer reacts with the MnPt layer, affecting the magnetic state. ３ After cap annealing of the Sn / MgO multilayer film, the MgO layer, which is the cap layer, is removed and then Mn ３ An MnPt / AlOx layer is formed on the Sn layer.

[0050] Next, the results of measuring a magnetic field using the magnetic sensor element 200 as a Hall element will be described. The multilayer film of the magnetic sensor element 200 used for the measurement was a MgO (110) substrate / W ​​(10 nm) / Mn ３ A Hall bar of Sn (15 nm) / MnPt (15 nm) / AlOx (5 nm) and 2 μm wide x 12 μm long was fabricated by photolithography.

[0051] 9A and 9B show the results of measuring the Hall effect obtained by applying a magnetic field of +2 T in the perpendicular direction at 450 K and then field cooling to 300 K.

[0052] FIG. 9A shows the Mn ３9A shows the dependence of the Hall resistivity of the Sn layer on the perpendicular magnetic field. It can be seen from FIG. 9A that the readout signal responds linearly to the magnetic field in a predetermined magnetic field range, including zero magnetic field (see dotted line). Specifically, the slope dρ Ｈ / dB=-0.0105 (μΩcm / mT).

[0053] Here, the three-layer W (10 nm) / Mn ３ The resistivity of Sn (15 nm) / MnPt (15 nm) was measured to be 156 μΩcm. Furthermore, from the measurement in the first embodiment, the resistivity of W was 40 μΩcm, and that of Mn ３ Since the resistivity of Sn is 200 μΩcm, the resistivity of MnPt is calculated to be 190 μΩcm.

[0054] FIG. 9B shows a pulse current of −5 mA (pulse width 0.5 ns) applied to the entire multilayer film (I write = -3mA, J ｗ =-15 MA / cm ２ ) was applied and the signal was read out at a current of 0.5 mA. ３ 9B shows the perpendicular magnetic field dependence of the Hall resistivity of the Sn layer. ３ It can be seen that the antiferromagnetic order of the Sn layer is reversed. In addition, a linear response is shown in the range of -100 mT to +100 mT (see dotted line), and the slope dρ Ｈ / dB=+0.0105 (μΩcm / mT).

[0055] Then, a +5 mA pulse current (pulse width 0.5 ns) was applied to the entire multilayer film (I write = +3mA, J ｗ = +15 MA / cm ２ ) is applied, Mn ３ The antiferromagnetic order in the Sn layer is reversed, returning to the hysteresis curve of FIG. 9A.

[0056] 9A and 9B are shifted in the magnetic field direction compared to the hysteresis loop shown in FIG. 6A of the first embodiment. This is because the MnPt layer of the bias layer 28 and the MnPt layer of the antiferromagnetic layer 14 are ３This means that an exchange bias occurs between the Sn layer and the hysteresis loop. It is difficult to measure a magnetic field in the normal hysteresis loop state as shown in Figure 6A. However, by shifting the hysteresis loop in the magnetic field direction using the exchange bias effect and adjusting the zero point in the linear response region to be near zero magnetic field, as shown in Figures 9A and 9B, it becomes possible to measure the magnetic field properly without generating a leakage magnetic field.

[0057] To remove background noise using the magnetic sensor element 200, a positive current and a negative current are alternately and repeatedly supplied to the heavy metal layer 12, and the difference between the resulting read signals is calculated.

[0058] Specifically, as shown in FIG. 10, a current supply unit 1002 supplies a positive current I write After supplying the read current I read is supplied, the Hall resistivity ρ Ｈ (+, B) or Hall voltage V Ｈ (+, B) (thick solid line) is obtained. Then, a negative current −I write After supplying the read current I read is supplied, the Hall resistivity ρ Ｈ (-, B) or Hall voltage V Ｈ (-, B) (thick solid line) is obtained. Positive current I write and negative current -I write By alternately and repeatedly supplying these, the magnetic order of the antiferromagnetic layer 14 transitions between two states due to the SOT.

[0059] The processor 1004 detects a positive current I write is supplied to the antiferromagnetic layer 14, and a negative current −I write is supplied to the antiferromagnetic layer 14, and the second read signal (Δρ Ｈ or ΔV Ｈ For example, when the first readout signal shown in FIG. 9A and the second readout signal shown in FIG. 9B are alternately obtained, the difference in Hall resistivity under a perpendicular magnetic field of 50 mT is calculated as Δρ Ｈ = ρ Ｈ(+, B)-ρ Ｈ (-, B) = 0.525 (μΩcm).

[0060] By repeating the operation shown in FIG. 10 at high speed (for example, in sub-nanoseconds) and performing the integration, the accuracy of noise removal can be improved and the signal-to-noise ratio can be increased.

[0061] It is also possible to employ a magnetic sensor element that does not undergo noise removal, as shown in Fig. 10. In this case, the heavy metal layer 12 is not required. Fig. 11A shows a magnetic sensor element 204 having a configuration in which the heavy metal layer 12 is removed from the magnetic sensor element 200 of Fig. 8A, and Fig. 11B shows a magnetic sensor element 206 having a configuration in which the heavy metal layer 12 is removed from the magnetic sensor element 202 of Fig. 8B.

[0062] In order to provide an antiferromagnetic layer with excellent response characteristics, it is preferable to reduce the coercive force of the antiferromagnetic layer, as described above. For example, the magnetic sensor element 208 shown in FIG. 12 is a multilayer film including a substrate 220, a heavy metal layer 222, an antiferromagnetic layer 224, a bias layer 228, and a cap layer 226, and the antiferromagnetic layer 224 is a layer of a granular first antiferromagnetic material. By dispersing the first antiferromagnetic material in granular form with a size of about 10 nm, the coercive force of the antiferromagnetic layer 224 can be reduced.

[0063] When an antiferromagnetic layer is provided as a continuous film (a film in which crystals are arranged without gaps), the coercive force can be reduced by making the film thinner, less than 10 nm.

[0064] 13 is a multilayer film of a substrate 230 / heavy metal layer 232 / antiferromagnetic layer 234 / bias layer 238 / cap layer 236, and the antiferromagnetic layer 234 is a single crystal film or an epitaxial film. The antiferromagnetic layer 234 has large crystalline domains, and the direction of the magnetic order of the first antiferromagnetic material is switched in a very weak magnetic field, and the switching of the domain wall propagates coherently. This can reduce the coercive force. Such an antiferromagnetic layer 234 has a gradient dρ in the linear response region near zero magnetic field. Ｈ / dB becomes steeper, the range of magnetic fields that can be measured becomes narrower, but the sensitivity becomes very high.

[0065] It should be noted that the heavy metal layers 222 and 232 are not necessarily required in the magnetic sensor elements 208 and 210 of FIGS.

[0066] Third Embodiment Next, a third embodiment of the present invention will be described with reference to Fig. 14 and Fig. 15. The magnetic sensor element of the third embodiment does not include a heavy metal layer and a bias layer.

[0067] 14 , the magnetic sensor element 300 of the third embodiment includes a substrate 30 made of an insulator, an antiferromagnetic layer 34 laminated on the substrate 30, and a cap layer 36 made of an oxide laminated on the antiferromagnetic layer 34. The antiferromagnetic layer 34 is made of a first antiferromagnetic material having an antiferromagnetic magnetic structure in which time-reversal symmetry is macroscopically broken, similar to the antiferromagnetic layers of the first and second embodiments. The antiferromagnetic layer 34 is a granular layer, and its thickness is approximately the same as the size of the grains.

[0068] Next, an example of a method for manufacturing the magnetic sensor element 300 will be described. ２ / Si substrate / Mn ３ An example is given in which a Sn (5 nm) / AlOx (10 nm) multilayer film is formed. Note that the thickness (nm) of each layer of the magnetic sensor element 300 is an example and is not limited thereto.

[0069] First, SiO ２ / Mn on Si substrate ３ A Sn (5 nm) layer was deposited at room temperature, where the chamber was maintained at a pressure of 0.5 Pa under an Ar atmosphere and the power was set to 60 W. Then, a Mn layer was deposited by DC sputtering. ３ An AlOx (10 nm) layer was deposited on the Sn (5 nm) layer at room temperature, where the chamber was maintained at a pressure of 0.3 Pa under an Ar atmosphere and the power was set to 100 W. Finally, a 5×10 －６ In a vacuum of 100 Pa, thermal oxidation of SiO ２ / Si substrate / Mn ３ The Sn (5 nm) / AlOx (10 nm) multilayer film is annealed at 500° C. for 30 minutes.

[0070] Next, the results of measuring a magnetic field using the magnetic sensor element 300 as a Hall element will be described. The multilayer film of the magnetic sensor element 300 used for the measurement is made of thermally oxidized SiO ２ / Si substrate / Mn ３ A Hall bar with a width of 2 μm and a length of 12 μm was fabricated by photolithography using Sn (5 nm) / AlOx (10 nm). ３ The resistivity of Sn is determined to be 250 μΩcm.

[0071] FIG. 15 shows the change in the Mn ３ This figure shows the dependence of the Hall resistivity of the Sn layer on the perpendicular magnetic field. From Figure 15, it can be seen that the readout signal responds linearly to the magnetic field in a predetermined magnetic field range including zero magnetic field (see dotted line). Specifically, the slope dρ Ｈ / dB=-0.016 (μΩcm / mT).

[0072] As mentioned above, thermally oxidized SiO ２ / Si substrate / Mn ３ When a Sn (5 nm) / AlOx (10 nm) multilayer film is fabricated, Mn ３ The Sn crystal grains become smaller, and the width of the hysteresis loop becomes almost zero near the zero magnetic field. Note that as the size of the Hall bar becomes smaller, the coercive force becomes even smaller.

[0073] In the third embodiment, unlike the first and second embodiments, there is no need to provide a heavy metal layer to pass a current or to provide a bias layer to shift the hysteresis curve, and good response characteristics can be achieved with a simple configuration.

[0074] In each of the magnetic sensor elements according to the first to third embodiments, a layer for preventing interlayer diffusion may be provided, and in the magnetic sensor element according to the second embodiment, a layer for enhancing the exchange bias effect may be provided.

[0075] The temperature range of the magnetic field measurement shown in the first to third embodiments can be controlled by substitution at the Mn and Sn sites. Ｈ / dB temperature change and Hall voltage VＨ The temperature change of can be tuned by substituting Mn and Sn.

[0076] In the above-described embodiments, the following methods for reducing the coercivity of the antiferromagnetic layer have been presented, but these methods can also be used in combination as appropriate: (i) Annealing the multilayer film after forming all layers of the multilayer film (cap annealing); (ii) Utilizing current-induced magnetic rotation of the antiferromagnetic layer (FIGS. 3 and 6B); (iii) Providing a granular layer as the antiferromagnetic layer (FIG. 12); (iv) Providing a continuous film (thin film) with a thickness of less than 10 nm as the antiferromagnetic layer; (v) Providing a single-crystal film or epitaxial film in which domain wall switching propagates coherently as the antiferromagnetic layer (FIG. 13).

[0077] According to the first to third embodiments, an antiferromagnetic layer made of a first antiferromagnetic material having an antiferromagnetic magnetic structure in which time reversal symmetry is macroscopically broken can provide a magnetic sensor element with excellent response characteristics by allowing the readout signal to respond linearly to the magnetic field within a predetermined magnetic field range including zero magnetic field.

[0078] Next, a magnetic sensor system will be described with reference to Fig. 16. The magnetic sensor system 2000 is a Hall element array in which a plurality of magnetic sensor elements 100 (Hall elements in Fig. 4) are arranged in an M x N matrix and connected in M ​​parallel and N series (M and N are positive integers).

[0079] The electrodes 18b of the M magnetic sensor elements 100 in the first column are connected to each other (the connection point is denoted as P), and the electrodes 18a of the M magnetic sensor elements 100 in the Nth column are connected to each other (the connection point is denoted as Q). The electrodes 17a of the M magnetic sensor elements 100 in the first column are connected to each other, and the electrodes 17b of the M magnetic sensor elements 100 in the Nth column are connected to each other.

[0080] In each row, the electrodes 18a and 18b of two adjacent magnetic sensor elements 100 are connected. As a result, the Hall voltages generated in the N magnetic sensor elements 100 in each row are added together. Also, in each row, the electrodes 17b and 17a of two adjacent magnetic sensor elements 100 are connected. As a result, the same current flows through the N magnetic sensor elements 100 in each row. If a current flows in the +x direction, the current I ＋ is branched into M, and in each row, the branch current flows through N magnetic sensor elements 100. The M branch currents join together to form a current I － The potential at point P is V ＋ and the potential V at point Q － The magnetic field can be measured by calculating the difference between

[0081] In the magnetic sensor system 2000, instead of the magnetic sensor element 100, other magnetic sensor elements shown in FIGS. 1B, 8A, 8B, and 11A to 14 may be employed.

[0082] When a magnetic sensor element having a bias layer is used in the magnetic sensor system 2000, the exchange bias of each magnetic sensor element will vary, but by arranging multiple magnetic sensor elements, it is expected that the variation in exchange bias can be canceled out without changing the resistance value of the entire system.

[0083] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention.

[0084] For example, in each of the above-described embodiments, examples have been shown in which the magnetic sensor elements are Hall elements, but these magnetic sensor elements can also be designed as TMR sensor elements.

[0085] 10, 30, 220, 230 Substrate 12, 222, 232 Heavy metal layer 14, 34, 224, 234 Antiferromagnetic layer 16, 26, 36, 226, 236 Cap layer 28, 228, 238 Bias layer 17a, 17b, 18a, 18b Electrode 100, 102, 200, 202, 204, 206, 208, 210, 300 Magnetic sensor element 1000 Magnetic sensor device 1002 Current supply unit 1004 Processor 1006 Memory 1008 Voltage detection unit 2000 Magnetic sensor system

Claims

1. A magnetic sensor element for measuring a magnetic field, comprising a first antiferromagnetic body having an antiferromagnetic magnetic structure with macroscopically broken time-reversal symmetry, and an antiferromagnetic layer having a readout signal that responds linearly to the magnetic field in a predetermined magnetic field range including zero magnetic field.

2. A magnetic sensor element as described in claim 1, further comprising a heavy metal layer in contact with the antiferromagnetic layer, made of a heavy metal, in which a spin current is generated in a direction perpendicular to the plane when a current flows in an in-plane direction, and in the antiferromagnetic layer, the magnetic order is controlled by a spin orbit torque generated by the spin current acting on the magnetic order of the first antiferromagnetic material.

3. A magnetic sensor element as described in claim 2, wherein the coercivity of the antiferromagnetic layer is reduced by passing a current through the heavy metal layer that exceeds a threshold current that causes current-induced magnetic rotation of the first antiferromagnet.

4. The magnetic sensor element according to claim 2, wherein the magnetic permeability of said antiferromagnetic layer is controlled based on the current density of the current flowing through said heavy metal layer.

5. The magnetic sensor element of claim 1, further comprising a bias layer in contact with the antiferromagnetic layer, the bias layer being made of a second antiferromagnetic material different from the first antiferromagnetic material and inducing an exchange bias with the first antiferromagnetic material.

6. The magnetic sensor element according to claim 1, wherein the antiferromagnetic layer is a granular layer.

7. The magnetic sensor element according to claim 1, wherein the antiferromagnetic layer is a continuous film having a thickness of less than 10 nm.

8. The magnetic sensor element according to claim 1, wherein the antiferromagnetic layer is a single crystal film or an epitaxial film.

9. The magnetic sensor element according to claim 1, wherein the antiferromagnetic layer is a polycrystalline film.

10. The magnetic sensor element according to claim 1, wherein the first antiferromagnetic material is a non-collinear antiferromagnetic material.

11. The magnetic sensor element of claim 1, wherein the antiferromagnetic layer exhibits an anomalous Hall effect, and the read signal from the antiferromagnetic layer is a signal based on the anomalous Hall effect.

12. A magnetic sensor device comprising: a magnetic sensor element according to claim 2; a current supply unit for supplying a current to the magnetic sensor element; and a processor for processing the read signal from the antiferromagnetic layer of the magnetic sensor element.

13. The magnetic sensor device of claim 12, wherein the current supply unit alternately supplies positive and negative currents to the heavy metal layer, and the processor calculates the difference between a first read signal from the antiferromagnetic layer when the positive current is supplied to the heavy metal layer and a second read signal from the antiferromagnetic layer when the negative current is supplied to the heavy metal layer.

14. The magnetic sensor device of claim 12, wherein the current supply unit alternately supplies to the heavy metal layer a first current greater than a critical current density providing a maximum magnetic permeability and a second current less than the critical current density, and the processor calculates the difference between a first read signal from the antiferromagnetic layer when the first current is supplied to the heavy metal layer and a second read signal from the antiferromagnetic layer when the second current is supplied to the heavy metal layer.

15. A magnetic sensor system in which a plurality of magnetic sensor elements are arranged, each of the plurality of magnetic sensor elements being defined as a magnetic sensor element according to any one of claims 1 to 11.

16. A method for producing a magnetic sensor element as described in claim 1, comprising forming a multilayer film including at least a substrate made of an insulator, a cap layer made of an oxide, and the antiferromagnetic layer provided between the substrate and the cap layer, and annealing the multilayer film after forming the multilayer film.

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