Three-dimensional magnetic sensor based on abnormal Hall effect

Abstract

The invention discloses a three-dimensional magnetic sensor based on an abnormal Hall effect, and belongs to the technical field of spin electron sensors. The three-dimensional magnetic sensor comprises a substrate, an AHE thin film material layer with PMA, a rare earth material layer, a protective layer and a metal electrode layer which are sequentially arranged from bottom to top, the AHE thin film material layer with PMA is of a Pt / Co / Pt multi-layer thin film heterostructure, and the rare earth material layer is Dy. According to the three-dimensional magnetic sensor based on the abnormal Hall effect provided by the invention, a rare earth material Dy layer with a proper thickness grows on a Pt / Co / Pt structure, Co and Dy form antiferromagnetic coupling based on RKKY interaction, residual magnetism adjustment driving current and power consumption are reduced, so that magnetic hysteresis is reduced, and the driving current and power consumption are correspondingly reduced; and the existence of RKKY interaction does not change the multilayer film PMA, so that the linear range is kept unchanged.

Description

Technical Field

[0001] The present invention belongs to the technical field of spin electron sensors, and in particular relates to a three-dimensional magnetic sensor based on the anomalous Hall effect. Background Art

[0002] Three-dimensional magnetic sensing technology is a core enabler for navigation and positioning, industrial non-destructive testing, and biomedical imaging. The key challenge lies in detecting magnetic field vector components with high precision and achieving miniaturized integration. Traditional approaches rely on two main technical approaches: one is a multi-sensor combination approach, which achieves three-dimensional magnetic field sensing by mechanically stacking three single-axis magnetic sensors in an orthogonal manner. For example, the cubic six-sided Hall array designed by Chen in 2007 reduced the error rate to 0.5%, but its size was millimeter-scale and required calibration algorithms to compensate for assembly errors. The other is a single-chip MEMS (Micro Electro Mechanical Systems) integration approach, which leverages semiconductor processing to achieve three-axis sensor integration on a single substrate. For example, in 2015, Van Jeng used silicon-based bevel trench etching technology to arrange GMR (Giant Magnetoresistance) sensors in an off-plane layout, achieving three-axis detection. While this structure reduces non-orthogonality errors, surface defects cause a 40% decrease in sensitivity.

[0003] Due to the sensitivity and integration bottlenecks of traditional technologies, research in three-dimensional magnetic sensing has shifted towards spintronic devices based on the AHE (Anomalous Hall Effect) and SOT (Spin Orbit Torque) effects. Compared to traditional Hall devices, AHE sensors with PMA (Perpendicular Magnetic Anisotropy) exhibit low resistivity, broadband response, and excellent thermal stability in out-of-plane magnetic field detection. Compared to sensors based on effects like GMR, they do not require complex biasing designs and offer a simpler fabrication process. In 2021, LiRuoFan et al. realized magnetic domain wall displacement modulation in Ta / CoFeB / MgO by jointly determining the direction and size of the SOT effective field by the current polarity and IP (In Plane) magnetic field. The AHE resistance, which is proportional to the magnetic moment in the z direction, was used to represent it. The linear relationship between the three-dimensional magnetic field and the AHE resistance was obtained by formula calculation, thereby realizing the measurement of the three-dimensional magnetic field. The sensitivities of this three-dimensional magnetic sensor in the x, y, and z directions are 205, 282, and 1.845VA, respectively. -1 T -1, and the linear ranges are ±10Oe, ±10Oe, and ±4Oe respectively. This type of device can achieve three-dimensional magnetic field linear response in a single-layer device and realize planar detection of the three-dimensional magnetic field through current drive.

[0004] To achieve greater sensitivity and linear range, in 2022, Guo et al. took advantage of the fact that the spin Hall angle of W is much larger than that of Ta and that the SOT is proportional to the spin Hall angle. They replaced Ta with W in Ta / CoFeB / MgO and obtained a SOT three-dimensional magnetic sensor with a larger linear range of ±20 Oe and a sensitivity of 625 V / (A·T) (z-axis). While achieving a larger linear range, the sensitivity was also reduced. In 2024, Ying Tao et al. used L10-FePt single-layer thin film with a larger anomalous Hall resistance to prepare a three-dimensional magnetic sensor. They measured a linear range of ±200 Oe in the x, y, and z directions and a sensitivity of 27.5 V / (A·T), 26.7 V / (A·T), and 291.2 V / (A·T). However, because the coercivity of this material is as high as 1 kOe, this method requires a large drive current to narrow the anomalous Hall resistance loop to coincide with each other to obtain a linear correspondence between the magnetic field and the resistance, resulting in excessive power consumption. The continuous increase in driving current causes the Joule heat to increase, and the magnetic moment inside the material is increasingly affected by thermal disturbances, resulting in the cancellation of magnetic moments in a certain direction, thereby reducing the coercive force.

[0005] Although three-dimensional magnetic sensors have made progress in terms of physical mechanisms, they still have problems: first, the magnetic field sensing range is small, and increasing the magnetic field sensing range is contrary to reducing the sensitivity; second, the existence of the sensor's large coercive force makes the driving current too high, which means that the power consumption is too high, making it difficult to be compatible with CMOS technology.

[0006] Synthetic antiferromagnetic (SAF) structures based on the RKKY (Ruderman-Kittel-Kasuya-Yosida) exchange interaction exhibit the advantages of zero stray fields and high stability similar to natural antiferromagnets, while also possessing the advantages of ferromagnets, such as ease of electrical control and magnetic signal detection. These materials are promising candidates for magnetic layers in spintronic devices. The RKKY exchange interaction manifests itself in a ferromagnetic / nonmagnetic / ferromagnetic (FM / NM / FM) sandwich structure as periodic oscillations of interferomagnetic coupling with a period of approximately 1 nm, triggered by changes in the thickness of the nonmagnetic spacer layer. SOT arises from the SOC (spin-orbit coupling) effect. For example, in a heavy metal / ferromagnetic multilayer structure, SOC converts charge flow in the heavy metal layer into spin currents that are injected into the ferromagnetic layer. These spins accumulate in the ferromagnetic layer, driving the magnetic moment of the magnetic layer to flip through the spin-orbit torque. Summary of the Invention

[0007] The purpose of the present invention is to address the problems in the background technology that increasing the magnetic field sensing range is inconsistent with reducing the sensitivity and the power consumption of the magnetic sensor is high. A three-dimensional magnetic sensor based on the anomalous Hall effect is proposed, which reduces the sensor power consumption and increases the sensor sensitivity while maintaining the linear sensing range unchanged.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A three-dimensional magnetic sensor based on the anomalous Hall effect includes a substrate, an AHE thin film material layer with PMA, a rare earth material layer, a protective layer, and a metal electrode layer arranged in sequence from bottom to top;

[0010] The AHE thin film material layer with PMA is a Pt / Co / Pt multilayer thin film heterostructure;

[0011] The rare earth material layer is Dy.

[0012] Furthermore, the substrate is a Si / SiO2 substrate that has been thermally oxidized.

[0013] Furthermore, the protective layer is Pt and has a thickness of 1 nm.

[0014] Furthermore, the metal electrode layer is a Cr / Au composite electrode with a thickness of 110 nm.

[0015] Furthermore, the thickness of the AHE thin film material layer having PMA is 3.6-7.2 nm.

[0016] Furthermore, the rare earth material layer Dy has a thickness of 1 to 8 nm, preferably 5 nm.

[0017] Furthermore, the AHE thin film material layer, rare earth material layer, protective layer and metal electrode with PMA are all prepared by magnetron DC sputtering. The sputtering power of the thin film material layer, rare earth material layer and protective layer is 10W, the sputtering power of the metal electrode is 30W, and the sputtering atmosphere is 0.3Pa argon.

[0018] Furthermore, the AHE thin film material layer, the rare earth material layer and the protective layer are formed into a cross-structured Hall-bar by photolithography and etching processes.

[0019] Furthermore, the metal electrode layer includes four metal electrodes located at four ends of the cross-structured Hall-bar.

[0020] The present invention provides a three-dimensional magnetic sensor based on the anomalous Hall effect. A rare earth material Dy layer (1-8 nm) is grown on a PMA-based AHE multilayer film structure (Pt / Co / Pt). The Dy layer serves as a spacer. The rare earth material exhibits weak magnetism. Co and Dy in this structure form an antiferromagnetic coupling based on the RKKY interaction without changing the PMA, maintaining the linear range while reducing the coercive force and thus device power consumption. Furthermore, Dy, as a rare earth element, exhibits strong spin-orbit coupling, enhancing the SOT effect of the film, further reducing power consumption and improving sensitivity.

[0021] The present invention provides a three-dimensional magnetic sensor based on the anomalous Hall effect. By growing a Dy layer of appropriate thickness, the coercive force can be reduced without changing the PMA, so that the linear range remains unchanged while reducing the drive current, thereby reducing power consumption. At the same time, the SOT effect is increased, the anomalous Hall resistance is enhanced, the drive current is reduced, and thus the power consumption is reduced and the sensitivity is improved.

[0022] Its working principle is:

[0023] A rare earth material Dy layer was grown as a spacer layer on a Pt / Co / Pt AHE thin film with PMA. When the Dy layer was 1 nm thick, the ultrathin Dy layer acted as an antiferromagnetic exchange coupling with the Co layer. Simultaneously, the rare earth material exhibited weak magnetic properties, causing the magnetic moments of the two layers to align antiparallel. The total magnetization canceled out after de-energization, resulting in a low coercivity. This is consistent with the oscillatory nature of the RKKY coupling, which varies with the thickness of the spacer layer. Further increasing the Dy layer to 8 nm caused the RKKY coupling strength to decay with distance, leading to interlayer decoupling. The Co layer then resumed independent magnetization reversal, and magnetic hysteresis reappeared. Therefore, this effect is thickness-dependent. With a thin Dy layer, Co and Dy form an antiferromagnetic coupling based on the RKKY interaction, reducing the coercivity and thus regulating the drive current and power consumption. However, this effect fails when the Dy layer is too thick. Furthermore, the presence of the RKKY interaction does not alter the PMA of the multilayer film, maintaining the linear range.

[0024] A rare earth material Dy layer is grown on the Pt / Co / Pt structure. As a rare earth element, Dy exhibits strong spin-orbit coupling, enhancing the film's SOT effect. The Dy 4f electron orbital hybridizes with the Pt 5d orbital, forming a stronger interfacial SOC. This increases the spin Hall angle, enhances the spin current injection efficiency, increases the SOT effect, and reduces the reversal current density. Furthermore, the introduction of the Dy layer imparts interfacial asymmetry to the multilayer film structure, enhancing the SOC of the Pt / Co structure, amplifying the SOT effect and leading to a redistribution of the Berry curvature, which in turn enhances the AHE response and increases the anomalous Hall resistance. In three-dimensional magnetic sensors driven by SOT-driven domain wall motion, the film's reversal ratio exhibits a linear relationship with increasing in-plane magnetic field. Because the reversal ratio is proportional to the anomalous Hall resistance, this linear relationship can be used to measure in-plane magnetic fields. Therefore, when the device measures the in-plane magnetic field, the smaller the current density required to drive the magnetization reversal, the smaller the power consumption required by the device; the larger the amplitude of the anomalous Hall resistance, the higher the sensitivity of the device, and the sensitivity is improved; combined with the RKKY effect, the linear sensing range remains unchanged, that is, the magnetic field sensing range remains unchanged.

[0025] Because the anomalous Hall effect (AHE) test doesn't directly measure the magnetic properties of a multilayer film, but rather indirectly through its electrical transport properties, it can be influenced by other factors (such as interface scattering). Therefore, a Dy layer of 1nm results in a near-zero coercivity when directly and accurately measuring its magnetic properties using a VSM. However, in an AHE test system, Dy values of 1 to 8nm can achieve a reduced coercivity. To achieve a synergistic balance between the RKKY interaction and the SOT in an AHE test system, a Dy of 5nm is optimal. A 5nm Dy layer maintains approximately 80% of the RKKY exchange strength through interface electronic state reconstruction, while maintaining a strong SOC that enhances the SOT effect. This also creates a gradient in the Berry curvature at the Co / Pt interface, tripling the AHE resistivity. Furthermore, a 5nm Dy layer doubles the spin Hall angle, enhancing the AHE effect. Therefore, a Dy of 5nm achieves the optimal synergy between RKKY and SOT.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention provides a three-dimensional magnetic sensor based on the anomalous Hall effect. A rare earth material Dy layer is grown on a Pt / Co / Pt structure. Through rare earth metal interface engineering, compared with other methods of increasing anomalous Hall resistance and reducing power consumption, the present invention can simultaneously reduce sensor power consumption, increase sensor sensitivity, and maintain the linear sensing range unchanged.

[0028] 2. The present invention provides a three-dimensional magnetic sensor based on the anomalous Hall effect. By growing a Dy layer of appropriate thickness, Co and Dy form an antiferromagnetic coupling based on the RKKY interaction, which reduces the remanent magnetization to adjust the driving current and power consumption, thereby reducing hysteresis and correspondingly reducing the driving current and power consumption. The presence of the RKKY interaction does not change the PMA of the multilayer film, so that the linear range remains unchanged.

[0029] 3. The present invention provides a three-dimensional magnetic sensor based on the anomalous Hall effect. By growing a Dy layer of appropriate thickness (1 to 8 nm) and utilizing the strong spin-orbit coupling characteristics of rare earth elements, the SOT effect of the film is enhanced, thereby increasing the anomalous Hall resistance and reducing power consumption. Combined with the RKKY effect, the linear sensing range remains unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic structural diagram of a three-dimensional magnetic sensor based on the anomalous Hall effect provided by the present invention;

[0031] Figure 2 A three-dimensional image (a) and a top view (b) of a three-dimensional magnetic sensor based on the anomalous Hall effect provided by the present invention;

[0032] Figure 3 The power consumption test results of sensors made with Dy layers of different thicknesses in the examples are shown in Figure 1; (a) Dy = 0 nm, (b) Dy = 1 nm, and (c) Dy = 8 nm.

[0033] Figure 4 The sensitivity test results of sensors with and without Dy layer growth are shown in Figure 1. (a) No Dy layer, (b) Dy layer thickness is 5 nm.

[0034] Figure 5 This is an experimental effect diagram of an embodiment of a three-dimensional magnetic sensor based on the anomalous Hall effect. DETAILED DESCRIPTION

[0035] The technical solutions of the present invention are described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited thereto.

[0036] Example

[0037] A three-dimensional magnetic sensor based on the anomalous Hall effect, such as Figure 1 As shown in FIG, it includes a substrate, an AHE thin film material layer with PMA, a rare earth material layer, a protective layer, and a metal electrode layer arranged in sequence from bottom to top; wherein the AHE thin film material layer with PMA is a Pt / Co / Pt multilayer thin film heterostructure, the rare earth material layer is Dy, and the protective layer is Pt. The three-dimensional image (a) and the top view (b) of the three-dimensional sensor are shown in FIG. Figure 2As shown, a cross-structured Hall-bar is formed by a photolithography and etching process. The Hall-bar line width is 20 microns, and the four ends of the Hall-bar are covered with metal electrodes.

[0038] The hysteresis loops of Pt(2nm) / Co(0.8nm) / Pt(1nm) and Pt(2nm) / Co(0.8nm) / Pt(1nm) / Dy(1nm / 8nm) multilayers were measured using VSM to demonstrate that the coercivity of the three-dimensional magnetic sensor can be regulated based on the RKKY exchange interaction, thereby reducing its driving current and power consumption. Figure 3 As shown in (a), when there is no Dy layer, the hysteresis loop shows obvious hysteresis; Figure 3 As shown in (b), when the Dy layer increases to 1 nm, the hysteresis loop shows zero coercivity, which is consistent with the oscillation characteristics of RKKY coupling as the thickness of the spacer layer changes; Figure 3 As shown in (c), when the Dy layer is further thickened to 8nm, hysteresis reappears. At the same time, the change in Dy thickness has little effect on the rectangularity of its hysteresis loop, that is, PMA, so that the linear range remains unchanged. Therefore, when a thinner Dy layer exists, Co and Dy in the multilayer film structure form antiferromagnetic coupling based on the RKKY interaction, reducing the coercive force. However, this effect is thickness-dependent and fails when the Dy layer is too thick. Therefore, the presence of a Dy layer of appropriate thickness reduces the coercive force, which can reduce the sensor drive current, thereby reducing power consumption while keeping the linear sensing range unchanged.

[0039] Compared with using VSM to directly measure the magnetic characteristics of multilayer films, the anomalous Hall loop cannot directly represent the magnetism of the multilayer film, but is indirectly reflected through the electrical transport characteristics, which may be affected by other factors. Therefore, 5nm Dy is selected for the experiment. Pt (2nm) / Co (0.8nm) / Pt (6nm) and Pt (2nm) / Co (0.8nm) / Pt (1nm) / Dy (5nm) / Pt (1nm) multilayer films are made into Hall-bar structure SOT devices through micro-nano processing technology. The current-induced reversal curves are tested under a planar magnetic field of ±400Oe. The results are shown in Figure 2. Figure 4 (a) and (b) show that compared with the case without Dy layer, the SOT switching current density decreases and the anomalous Hall resistance increases when 5nm Dy layer is present, indicating that the SOT efficiency is higher and the SOT effect is enhanced. xThe flip ratio increases linearly with the increase in the anomalous Hall resistance, and this linear relationship can be used to measure the in-plane magnetic field. Therefore, when the device measures the in-plane magnetic field, the smaller the current density required to drive the magnetization flip, the lower the power consumption required by the device; the larger the anomalous Hall resistance amplitude, the higher the sensitivity of the device, and the magnetic field sensing range remains unchanged while the sensitivity increases. Therefore, the presence of a Dy layer of appropriate thickness reduces the coercive force, which can reduce the sensor drive current and thus reduce power consumption. Combined with the RKKY effect, it maintains the linear sensing range unchanged.

[0040] As shown in the anomalous Hall loops of Pt(2nm) / Co(0.8nm) / Pt(6nm) and Pt(2nm) / Co(0.8nm) / Pt(1nm) / Dy(5nm) / Pt(1nm) multilayer films, the magnetic field is in the z direction, as shown in Figure 5 As shown in the figure, compared with the Pt / Co / Pt multilayer film without the Dy layer, the multilayer film with a 5nm Dy layer has a reduced coercive force, an increased anomalous Hall resistance, and an unchanged PMA characteristic. Therefore, the presence of a 5nm thick Dy layer can reduce the sensor driving current, thereby reducing power consumption while maintaining the linear sensing range unchanged.

Claims

1. A three-dimensional magnetic sensor based on the anomalous Hall effect, characterized in that: The method comprises a substrate, an AHE thin film material layer having PMA, a rare earth material layer, a protective layer and a metal electrode layer which are sequentially arranged from bottom to top; The AHE thin film material layer with PMA is a Pt / Co / Pt multilayer thin film heterostructure; The rare earth material layer is Dy.

2. The three-dimensional magnetic sensor based on the anomalous Hall effect according to claim 1, characterized in that: The substrate is a Si / SiO2 substrate that has been subjected to thermal oxidation treatment.

3. The three-dimensional magnetic sensor based on the anomalous Hall effect according to claim 1, characterized in that: The protective layer is Pt and has a thickness of 1 nm.

4. The three-dimensional magnetic sensor based on the anomalous Hall effect according to claim 1, characterized in that: The metal electrode layer is a Cr / Au composite electrode with a thickness of 110 nm.

5. The three-dimensional magnetic sensor based on the anomalous Hall effect according to claim 1, characterized in that: The thickness of the AHE thin film material layer with PMA is 3.6-7.2 nm.

6. The three-dimensional magnetic sensor based on the anomalous Hall effect according to claim 1, characterized in that: The thickness of the rare earth material layer Dy is 1-8 nm.

7. The three-dimensional magnetic sensor based on the anomalous Hall effect according to claim 1, characterized in that: The AHE thin film material layer, rare earth material layer, protective layer and metal electrode with PMA are all prepared by magnetron DC sputtering. The sputtering power of the thin film material layer, rare earth material layer and protective layer is 10W, the sputtering power of the metal electrode is 30W, and the sputtering atmosphere is 0.3Pa argon.

8. The three-dimensional magnetic sensor based on the anomalous Hall effect according to claim 1, characterized in that: The AHE thin film material layer, the rare earth material layer and the protective layer are formed into a cross-structured Hall-bar through a photolithography and etching process.

9. The three-dimensional magnetic sensor based on the anomalous Hall effect according to claim 1, characterized in that: The metal electrode layer includes four metal electrodes located at four ends of the cross-structured Hall-bar.

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