A two-dimensional heterojunction device based on intrinsic spin-orbital moment for global field-free flipping and a preparation method

Abstract

The application belongs to the technical field of spin electronic devices, and particularly relates to a two-dimensional heterojunction device based on intrinsic spin-orbital moment for realizing global field-free flipping and a preparation method. The two-dimensional heterojunction device comprises a metal electrode, a two-dimensional ferromagnetic layer covering a channel region of the metal electrode and comprising FGaT material, and a two-dimensional antiferromagnetic layer covering a local region of the two-dimensional ferromagnetic layer, so that the two-dimensional ferromagnetic layer forms a covered first region and an uncovered second region and comprises CrSBr material. When a pulse current is applied along the channel direction under zero external magnetic field, the two-dimensional heterojunction device is cooperated by the intrinsic spin-orbital moment of FGaT and the in-plane exchange bias induced by CrSBr, and the first region and the second region have consistent deterministic magnetic moment flipping. In the case of no heavy metal layer and no external magnetic field, the global field-free flipping is realized by local antiferromagnetic bias induction and global intrinsic spin-orbital moment driving.

Description

Technical Field

[0001] This invention belongs to the field of spintronic device technology, and particularly relates to a two-dimensional heterojunction device and its fabrication method that achieves global field-free flipping based on intrinsic spin orbital moments. Background Technology

[0002] Spin-orbit moment reversal is a crucial physical foundation for novel magnetic storage, spin logic, and magnetic random access memory devices. Traditional spin-orbit moment devices typically rely on heavy metal layers or topological materials such as Pt, Ta, and W to provide spin current, and often require an external in-plane magnetic field to achieve deterministic reversal. Although these devices have been extensively studied, they generally suffer from problems such as complex device stacking, significant interface scattering losses, difficulties in on-chip integration with external fields, and high power consumption.

[0003] In traditional heavy metal / ferromagnetic layer spin orbital torque (SOT) systems, the spin current is mainly generated by the spin Hall effect in the heavy metal layer or the interface Rashba effect, and the resulting spin orbital torque is usually concentrated near the heavy metal / ferromagnetic layer interface. For ferromagnetic layers with perpendicular magnetic anisotropy, under zero external magnetic field conditions, the upward and downward magnetization states usually have approximately symmetrical energy states. The current-induced damped torque is difficult to distinguish between the two opposite magnetization directions, and therefore cannot stably select a unique flipping final state. To break this symmetry, traditional systems generally require the application of an additional in-plane magnetic field, the introduction of complex wedge structures, antiferromagnetic pinning layers, low-symmetry spin source layers, or local exchange bias structures. Although the above schemes can achieve field-free flipping in local regions, their driving torque or effective field is often limited by the spin diffusion length, interface coverage, and local structural design, making it difficult to maintain the same flipping ratio and critical current density between the uncovered and covered regions. Therefore, it is difficult to achieve global field-free flipping of the entire continuous ferromagnetic channel.

[0004] In recent years, the development of two-dimensional van der Waals magnetic materials has provided a new platform for constructing low-dimensional, clean-interface magnetoelectronic devices. Existing work has shown that in Pt / (Co... 0.5 Fe 0.5 ) 5-x In systems such as GeTe2 / CrSBr, the in-plane antiferromagnetic material CrSBr can provide an equivalent in-plane field, enabling field-free flipping. However, such schemes still rely on Pt as the spin source layer, and the former focuses on (Co) 0.5 Fe 0.5 ) 5-x The Néel vector or multilayer antiferromagnetic correlation behavior in GeTe2 does not directly utilize the intrinsic spin orbital moment of the two-dimensional ferromagnetic material itself, and it is difficult to achieve a global field-free flip without heavy metal layers.

[0005] Therefore, there is an urgent need to develop a novel heterojunction device and control method that does not require a heavy metal layer or an external magnetic field, directly utilizes the intrinsic spin orbital moment of the two-dimensional ferromagnetic material itself, and can achieve global field-free reversal with the help of a local two-dimensional antiferromagnetic layer. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a two-dimensional heterojunction device and its fabrication method that achieves global field-free flipping based on intrinsic spin orbit moments, thereby solving the problem that existing spin orbit moment devices rely on heavy metal layers and external magnetic fields, making it difficult to achieve globally consistent flipping.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a two-dimensional heterojunction device that achieves global field-free flipping based on intrinsic spin orbital moments, comprising: A metal electrode, comprising a source electrode, a drain electrode, and a channel region located between the source electrode and the drain electrode; A two-dimensional ferromagnetic layer covers the channel region of the metal electrode, and its composition includes Fe3GaTe2 material; A two-dimensional antiferromagnetic layer is applied to a local area of ​​the two-dimensional ferromagnetic layer, forming a covered first region and an uncovered second region of the two-dimensional ferromagnetic layer. Its composition includes CrSBr material.

[0008] Optionally, the two-dimensional heterojunction device can achieve deterministic magnetic moment reversal under zero external magnetic field.

[0009] Optionally, when a pulsed current is applied along the channel direction under zero external magnetic field, the two-dimensional heterojunction device exhibits consistent deterministic magnetic moment reversal in its first and second regions due to the synergistic effect of the intrinsic spin orbital moment of Fe3GaTe2 and the in-plane exchange bias induced by CrSBr.

[0010] Optionally, the area of ​​the first region accounts for more than 10% of the total area of ​​the two-dimensional ferromagnetic layer.

[0011] Optionally, the metal electrode further includes multiple pairs of Hall detector ends arranged along the channel direction, wherein at least one pair is located in the first region and at least another pair is located in the second region; The first region and the second region have consistent deterministic magnetic moment reversal, which includes: when a pulse current is applied along the channel direction, the error of the anomalous Hall resistance reversal signal observed by the Hall detectors arranged in the first region and the second region relative to the average value of the anomalous Hall resistance reversal signal observed by each Hall detector is within ±5%.

[0012] Optionally, the device does not contain a heavy metal layer.

[0013] Optionally, it also includes a protective layer that at least covers the upper surface of the two-dimensional antiferromagnetic layer, the protective layer being made of hexagonal boron nitride material.

[0014] Optionally, the anomalous Hall resistor flip signal is a flip ratio or a critical flip current density.

[0015] In a second aspect, the present invention provides a method for fabricating the two-dimensional heterojunction device described in the first aspect, comprising: Fabricating metal electrodes on a substrate; The Fe3GaTe2 material is transferred onto the metal electrode to cover the channel region, forming the two-dimensional ferromagnetic layer. The CrSBr material is transferred to a local area on the surface of the Fe3GaTe2 material to form the two-dimensional antiferromagnetic layer; thus, the two-dimensional heterojunction device can be obtained.

[0016] Thirdly, the present invention provides a verification method for the global field-free flipping of the two-dimensional heterojunction device described in the first aspect, comprising: Under zero external magnetic field conditions, a pulsed current is applied along the channel direction, and during the process, the anomalous Hall resistance of the Hall detection terminal in the first region and the second region is measured simultaneously; If the anomalous Hall resistance reversal signals of the first region and the second region are consistent, it proves that the two-dimensional heterojunction device can achieve global field-free reversal.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: The Fe3GaTe2 (FGaT) two-dimensional van der Waals ferromagnetic material used in this invention possesses intrinsic structural symmetry breaking, such as the upward shift of Fe atoms, local inversion symmetry breaking induced by Fe vacancies, and the resulting large Berry curvature. This allows current to directly generate intrinsic spin orbital moments within the FGaT. These intrinsic spin orbital moments do not depend on spin current injected from an external heavy metal layer, nor are they limited to a specific heavy metal / ferromagnetic interface. Instead, they originate from the FGaT's own band structure and internal symmetry breaking, thus enabling effective driving forces for magnetic moments at different positions within continuous FGaT channels. Furthermore, the in-plane antiferromagnetic order of CrSBr induces in-plane exchange bias in adjacent FGaT regions through van der Waals interface exchange coupling. This exchange bias provides the additional symmetry breaking required for zero external magnetic field reversal, allowing the current-induced intrinsic spin orbital moment (SOT) to deterministically select the reversal direction. Because the FGaT layer is a continuous two-dimensional ferromagnetic layer, its internal exchange coupling can transfer the magnetic pinning and orientation reversal induced by local CrSBr to regions not covered by CrSBr. Simultaneously, the intrinsic SOT spin-orbit torque acts throughout the entire FGaT layer, enabling both CrSBr-covered and CrSBr-un-covered FGaT regions to achieve the same reversal. Without the need for a heavy metal layer or an external magnetic field, a global field-free reversal induced by local antiferromagnetic bias and driven by the intrinsic spin-orbit torque across the entire channel is achieved, solving the problem of global controllability in traditional systems with local exchange bias or external spin sources. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a single FGaT device according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the FGaT / CrSBr heterojunction device according to Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the structure of the FGaT / CrSBr heterojunction device with a multi-Hall port according to Embodiment 3 of the present invention; Figure 4 This is a schematic diagram of the FGaT / CrSBr heterojunction device used to illustrate different Hall port positions in Example 3; Figure 5The figure shows the test results of a single FGaT device in Embodiment 1 of the present invention at a field-controlled flip-flop test at 50K. Figure 6 The figure shows the field-free flip-over test results of the FGaT / CrSBr heterojunction device in Embodiment 2 of the present invention at 50K. Figure 7 This is a comparison of the flipping test results of different Hall ports of the FGaT / CrSBr heterojunction device with multiple Hall ports in Embodiment 3 of the present invention under different in-plane magnetic fields at a temperature of 50K. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] Example 1: Verification of field flipping and characterization of intrinsic spin orbital moment in a single FGaT device This embodiment aims to verify the existence of intrinsic spin orbital moments in FGaT.

[0024] The method for fabricating the above-mentioned single FGaT device includes the following steps: Step 1: Prepare metal electrodes Step 1.1: Cut the silicon wafer with the 285nm oxide layer into 0.8cm×0.8cm pieces, and place them in beakers containing acetone and ethanol in sequence. Clean the silicon wafer with an ultrasonic cleaner for 2 minutes, and then dry it with nitrogen gas.

[0025] Step 1.2: Place the cleaned silicon wafer on a spin coater and spin-coate it sequentially with methyl methacrylate (MMA) EL6 and polymethyl methacrylate (PMMA) A5 photoresist. After the first layer of EL6 is spin-coated and baked, a second layer of A5 photoresist is spin-coated. The spin coater speed is set in stages: the first stage is at 4000 rpm for 33 seconds, and the second stage is at 7000 rpm for 8 seconds. After each spin coat, place the silicon wafer on a heated platform and dry it at 120°C for 2 minutes.

[0026] Step 1.3: Use DrawBeam software to draw the required Hall bar electrode pattern, place the silicon wafer with spin-coated photoresist into the electron beam exposure machine cavity, and evacuate to 10°C. -6 Below the Pa level, a silicon wafer with a target electrode pattern is obtained by bombarding a silicon wafer with photoresist using an electron beam. The Hall electrode has a width of 2 μm.

[0027] Step 1.4: Immerse the exposed silicon wafer in the developer for 35 seconds to remove the photoresist that has been denatured after electron beam exposure. Then, fix the silicon wafer in isopropanol for 10 seconds and finally dry it with nitrogen gas.

[0028] Step 1.5: Place the silicon wafer, after exposure and development, into the cavity of the electron beam evaporation system and evacuate to 6×10⁻⁶. -4 After the Pa is below a certain value, titanium with a thickness of 5 nm is first deposited using an electron beam evaporation system (rate 0.15 Å / s), and then gold with a thickness of 25 nm is deposited using a thermal evaporation system (rate 0.5 Å / s). After the evaporation is completed, the silicon wafer is removed.

[0029] Step 1.6: Immerse the deposited silicon wafer in acetone solution for about 10 minutes, peel off the unexposed parts, and the remaining part is the required metal electrode.

[0030] Step 2: Transfer FGaT material and protective layer Step 2.1: Take a bulk FGaT material and obtain a thin film using a mechanical peeling method. Use tweezers to pick up a small piece of bulk FGaT and apply it to adhesive tape. Fold the tape repeatedly, then adhere it to the polydimethylsiloxane film attached to the glass slide and separate them to obtain a polydimethylsiloxane film with FGaT thin films attached. Place the glass slide with the polydimethylsiloxane film under an optical microscope for observation, and select FGaT samples with uniform thickness and clean surfaces.

[0031] Step 2.2: Attach the substrate of the metal electrode prepared in Step 1 onto the cut silicon wafer and fix it in the center of the sample stage in the transfer platform. Invert a glass slide containing the polydimethylsiloxane film with the FGaT sample and place it above the electrode. Using a microscope for precise alignment, bring the sample into contact with the electrode channel region. Then, slowly lift the glass slide to transfer the FGaT sample onto the metal electrode and completely cover the channel region, completing the fabrication of a single FGaT device. Its structural schematic diagram is shown below. Figure 1 As shown, the thickness of FGaT is preferably 30 to 50 nm (in this embodiment, the thickness is 50 nm).

[0032] Step 2.3: Take a hexagonal boron nitride bulk material and obtain a thin film using a mechanical peeling method. Obtain a hexagonal boron nitride thin film using a polydimethylsiloxane film adhered to a glass slide. Invert the glass slide with the polydimethylsiloxane film of hexagonal boron nitride onto the FGaT and accurately align it with a microscope. Cover the upper surface of the FGaT with the hexagonal boron nitride thin film to protect the entire device. The device fabrication is now complete.

[0033] Step 3: Field Flip Test Step 3.1: Place the prepared single FGaT device into a low-temperature measurement system and cool it to 50K.

[0034] Step 3.2: Apply a pulsed current along the channel direction while simultaneously applying an external magnetic field perpendicular to it, and measure the curve of the anomalous Hall resistance as a function of the external magnetic field. The results are as follows: Figure 5 As shown, obvious hysteresis loops and magnetic moment reversal behavior can be observed under the assistance of an external magnetic field, proving that FGaT has a magnetic moment that can be controlled by current.

[0035] Furthermore, the field-flipped results of a single FGaT device demonstrate that, even without the introduction of a heavy metal spin source layer, FGaT can still generate an effective magnetic moment flipping response under the influence of current, indicating that FGaT possesses an intrinsic spin orbital moment that can be used to drive magnetization control. This intrinsic spin orbital moment is related to the upward shift of Fe atom positions within FGaT, the symmetry breaking induced by Fe vacancies, and the large Bailey curvature, providing a driving force for subsequent field-free flipping without a heavy metal layer in FGaT / CrSBr heterojunctions.

[0036] Example 2: Field-free flip-flop of FGaT / CrSBr two-dimensional heterojunction device This embodiment aims to verify the field-free flipping achieved in an FGaT / CrSBr heterojunction using in-plane exchange bias.

[0037] Steps 1-2: Same as in Example 1, prepare a substrate with metal electrodes and transfer FGaT material. Step 3: Transfer CrSBr material and protective layer Step 3.1: Take a CrSBr bulk material and obtain a thin film using a mechanical exfoliation method. Use tweezers to pick up a small piece of CrSBr bulk material, apply it to adhesive tape, fold the tape repeatedly, and attach a polydimethylsiloxane film (PDSBr) adhered to a glass slide to the tape to obtain a PDSBr film with the CrSBr thin film attached. Select CrSBr samples with uniform thickness and clean surfaces under an optical microscope. The thickness of the CrSBr thin film is 100 nm.

[0038] Step 3.2: Invert a glass slide containing a polydimethylsiloxane film coated with CrSBr sample and place it above the electrode on which FGaT has been transferred. Using a microscope, precisely align the slide to ensure that a portion of the CrSBr sample contacts and adheres to the FGaT layer. In the direction perpendicular to the channel, CrSBr is in complete contact with the FGaT layer; in the direction parallel to the channel, CrSBr extends beyond the FGaT layer. The ratio of the overlap area of ​​CrSBr and FGaT to the area of ​​the FGaT sheet itself (i.e., the coverage area ratio) is at least greater than 6% (in this embodiment, the overlap area accounts for 31.3% of the FGaT sheet's area). Then, slowly lift the glass slide to transfer the CrSBr sample to the upper surface of the FGaT layer, forming an FGaT / CrSBr heterojunction, where CrSBr covers a portion of the FGaT layer. This yields a two-dimensional heterojunction device that achieves global field-free flipping based on intrinsic spin orbital moments. A schematic diagram of its structure is shown below. Figure 2 As shown (i.e., FGaT / CrSBr two-dimensional heterojunction device).

[0039] Step 3.3: Take a block of hexagonal boron nitride and obtain a thin film using mechanical peeling. Obtain a hexagonal boron nitride thin film using a polydimethylsiloxane film adhered to a glass slide. Invert the glass slide with the polydimethylsiloxane film of hexagonal boron nitride and place it above the heterojunction. With precise alignment using a microscope, cover the surface of the heterojunction with the hexagonal boron nitride thin film to protect the entire device. The device fabrication is now complete.

[0040] Step 4: Field-free flipping test Step 4.1: Place the prepared FGaT / CrSBr two-dimensional heterojunction device into the low-temperature measurement system and cool it to 50K. Apply a +1 T magnetic field in the out-of-plane direction perpendicular to the sample surface to initialize it.

[0041] Step 4.2: Apply a pulsed current along the channel direction and measure the anomalous Hall resistance as a function of current without applying an external magnetic field. Since CrSBr possesses in-plane antiferromagnetic order, it can provide an in-plane exchange bias at the FGaT / CrSBr interface, thus achieving deterministic field-free flipping of the FGaT layer without an external magnetic field. This invention removes the Pt spin source layer, yet flipping still occurs, indicating that the driving force comes from the coupling between the intrinsic spin-orbit coupling of FGaT and the CrSBr exchange bias.

[0042] Step 4.2.1: In specific control, a forward and reverse sweep current is applied between the source and drain electrodes along the channel direction. The current density is gradually swept from a negative value to a positive value, and then back from a positive value to a negative value, or the opposite sweep direction is used. During the sweep current process, the anomalous Hall resistance is measured simultaneously to obtain the hysteresis loop of the anomalous Hall resistance as a function of the current density. If, under zero external magnetic field conditions, the anomalous Hall resistance exhibits repeatable hysteresis transitions with the positive and negative sweep currents, then it is determined that a deterministic field-free reversal has occurred in the magnetization direction of FGaT.

[0043] Step 4.2.2: By changing the direction of the initial magnetic field or the direction of the pulse current, the polarity of the anomalous Hall resistor can be reversed accordingly. This indicates that the in-plane exchange bias induced by CrSBr provides the symmetry breaking required to distinguish two opposite magnetization directions under zero external magnetic field conditions, while the intrinsic spin orbital moment of FGaT itself provides the main current driving torque.

[0044] The results are as follows Figure 6 As shown, a clear hysteresis loop and magnetic moment reversal behavior can be observed under zero magnetic field conditions. The reversal polarity reverses with the change of current direction, proving the realization of field-free reversal. The critical current density is at 10. 6 A / cm 2 This invention achieves low-power magnetic moment reversal at an order of magnitude. In this system, the field-free reversal does not rely on the spin current generated by external heavy metal layers such as Pt, Ta, or W, but is achieved jointly by the intrinsic spin-orbit torque of FGaT and the in-plane exchange bias induced by CrSBr. Traditional systems typically struggle to achieve deterministic reversals under zero external magnetic field due to the symmetry of the upper and lower magnetization states. However, this invention breaks this symmetry by providing an in-plane exchange bias through CrSBr, and generates an effective spin-orbit torque through the breaking of the intrinsic symmetry of FGaT and its large Berry curvature, thus enabling deterministic reversals without an external magnetic field.

[0045] Example 3: Global Field-Free Flip of Multi-Hall Port FGaT / CrSBr Heterojunction Device This embodiment aims to verify the nonlocality of the intrinsic spin orbital moment, proving that global field-free flipping can be achieved with only local antiferromagnetic pinning.

[0046] Step 1: Fabrication of a metal electrode with five pairs of Hall ports Steps 1.1-1.6 are basically the same as in Example 1, except that the electrode pattern drawn in step 1.3 includes five pairs of Hall detectors, which are arranged at equal intervals along the channel direction and are labeled as T1, T2, T3, T4 and T5 respectively.

[0047] Step 2: Transfer FGaT material Similar to step 2 of Example 1, the FGaT sample is transferred onto the metal electrode, completely covering the channel region and all Hall ports.

[0048] Step 3: Transfer CrSBr material and protective layer Step 3.1: Same as step 3.1 in Example 2, obtain CrSBr sample.

[0049] Step 3.2: Invert the glass slide containing the polydimethylsiloxane film coated with CrSBr sample and place it above the electrode with transferred FGaT. Using a microscope for precise alignment, transfer the CrSBr sample to a position near end T1, covering only a portion of the FGaT area, ensuring that at least ports T3, T4, and T5 are not below the overlapping area of ​​the heterojunction. End T5 is furthest from the CrSBr-covered area, resulting in a two-dimensional FGaT / CrSBr heterojunction device with multiple pairs of Hall ports. A schematic diagram of its structure is shown below. Figure 3 , Figure 4 As shown.

[0050] Step 3.3: Take a block of hexagonal boron nitride and obtain a thin film using mechanical peeling. Obtain a hexagonal boron nitride thin film using a polydimethylsiloxane film adhered to a glass slide. Invert the glass slide with the polydimethylsiloxane film of hexagonal boron nitride and place it above the heterojunction. With precise alignment using a microscope, cover the surface of the heterojunction with the hexagonal boron nitride thin film to protect the entire device. The device fabrication is now complete.

[0051] Step 4: Electrical transmission test Step 4.1: Place the prepared multi-Hall port FGaT / CrSBr heterojunction device into a low-temperature measurement system and cool it to 50K.

[0052] Step 4.1.1: During the cooling process, apply in-plane field cooling along the channel direction, preferably with a magnitude of +0.1T or -0.1T, so that the CrSBr local coverage area is induced to have an in-plane exchange bias in a defined direction in FGaT; then remove the external magnetic field so that different Hall ports such as T1, T3 and T5 are all under zero external magnetic field measurement conditions.

[0053] Step 4.2: Apply a pulsed current along the channel direction. Without applying an external magnetic field, select three Hall ports at positions from near to far of the CrSBr region for testing, denoted as T1, T3, and T5 respectively. The test results are as follows: Figure 7 As shown, the results indicate that field-free flipping behavior can be observed at T1, T3, and T5, and the flipping ratio and critical current density are essentially the same. This demonstrates that the intrinsic spin-orbit moments in FGaT possess nonlocal characteristics, and the pinning of local regions by CrSBr can be transferred and act on the entire FGaT layer, thereby achieving global field-free flipping. This characteristic is of great significance for simplifying device fabrication and improving integration density.

[0054] Step 4.2.1: Specifically, positive and negative sweep currents are applied along the channel direction between the source and drain electrodes, and the curves of the anomalous Hall resistance at ports T1, T3, and T5 as a function of current density are recorded during the sweep current process. By comparing the hysteresis loops at ports T1, T3, and T5, it is determined whether current-driven magnetization reversal occurs in the FGaT regions corresponding to different spatial locations.

[0055] Step 4.2.2: When the CrSBr-covered area corresponding to port T1, the middle area corresponding to port T3, and the area far from the CrSBr-covered area corresponding to port T5 all exhibit substantially the same flip ratio (within ±5% of the average error of the anomalous Hall resistance flip ratio observed by Hall detectors across all Hall ports) and substantially the same critical current density (within ±5% of the average error of the critical current density observed by Hall detectors across all Hall ports), it is confirmed that the local CrSBr coverage is sufficient to produce a consistent zero-field flip across the entire FGaT continuous channel. This criterion differs from traditional local field-free flips. In this invention, the area not directly covered by CrSBr also exhibits the same flip behavior as the covered area, thus belonging to global field-free flips.

[0056] Mechanistically, the CrSBr-covered region provides an in-plane exchange bias to the adjacent FGaT region through interfacial exchange coupling. This in-plane exchange bias breaks the equivalence of the vertical magnetization upward and downward states under zero external magnetic field. FGaT exhibits significant Berry curvature due to the upward shift of Fe atoms, Fe vacancies, and the breaking of inversion symmetry within the crystal. When current flows through FGaT, it can generate intrinsic spin-orbit moments within the material. Since FGaT is a continuous two-dimensional ferromagnetic layer, intralayer exchange coupling and domain wall propagation allow the locally biased flip orientation to extend to regions far from CrSBr. Simultaneously, the intrinsic spin-orbit moment is a bulk or full-channel effective torque generated by FGaT itself, unrestricted by the external heavy metal spin injection interface. Therefore, it can drive magnetic moment flips in both CrSBr-covered and uncovered regions. Thus, even if CrSBr only covers a portion of the FGaT, the entire FGaT channel can still exhibit globally consistent field-free flips.

[0057] The reason why traditional systems cannot achieve the aforementioned global field-free flip is twofold: First, the spin-orbit torque in traditional heavy metal / ferromagnetic bilayers is mainly generated by the heavy metal layer and injected into the ferromagnetic layer, and its range of influence is limited by interface quality, spin diffusion length, and the area covered by the heavy metal. Second, without an external in-plane magnetic field, the two stable magnetization directions of the perpendicularly magnetized ferromagnetic layer lack a deterministic selection mechanism, easily leading to random flips, inconsistent domain nucleation, or only local flips. Therefore, current technologies cannot achieve a global field-free flip where the covered and uncovered regions flip simultaneously and consistently under conditions of no heavy metal layer, no external magnetic field, and local antiferromagnetic coverage.

[0058] As can be seen from the above embodiments, this invention provides a global field-free flipping scheme for two-dimensional van der Waals heterojunction devices based on the intrinsic spin-orbit moment of the two-dimensional van der Waals ferromagnetic material and the in-plane exchange bias induced by the two-dimensional van der Waals in-plane antiferromagnetic material. Compared with existing spin-orbit moment devices that rely on heavy metal layers and external magnetic fields, the device structure of this invention is simpler and has higher integration potential. This invention demonstrates through multi-Hall port testing that both the port closest to the CrSBr coverage region and the port furthest from the CrSBr coverage region can undergo consistent flipping under zero external magnetic field, indicating that this invention does not only achieve local field-free flipping, but also achieves global field-free flipping within the entire continuous FGaT ferromagnetic channel.

[0059] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A two-dimensional heterojunction device that achieves global field-free flipping based on intrinsic spin orbital moments, characterized in that, include: A metal electrode, comprising a source electrode, a drain electrode, and a channel region located between the source electrode and the drain electrode; A two-dimensional ferromagnetic layer covers the channel region of the metal electrode, and its composition includes Fe3GaTe2 material; A two-dimensional antiferromagnetic layer is applied to a local area of ​​the two-dimensional ferromagnetic layer, forming a covered first region and an uncovered second region of the two-dimensional ferromagnetic layer. Its composition includes CrSBr material.

2. The two-dimensional heterojunction device according to claim 1, characterized in that, The device does not contain a heavy metal layer.

3. The two-dimensional heterojunction device according to claim 1, characterized in that, The two-dimensional heterojunction device can achieve deterministic magnetic moment reversal under zero external magnetic field.

4. The two-dimensional heterojunction device according to claim 1, characterized in that, When a pulsed current is applied along the channel direction under zero external magnetic field, the two-dimensional heterojunction device exhibits consistent deterministic magnetic moment reversal in its first and second regions due to the synergistic effect of the intrinsic spin orbital moment of Fe3GaTe2 and the in-plane exchange bias induced by CrSBr.

5. The two-dimensional heterojunction device according to claim 1, characterized in that, The area of ​​the first region accounts for more than 10% of the total area of ​​the two-dimensional ferromagnetic layer.

6. The two-dimensional heterojunction device according to claim 1, characterized in that, The metal electrode also includes multiple pairs of Hall detector ends arranged along the channel direction, wherein at least one pair is located in the first region and at least another pair is located in the second region; The first region and the second region have consistent deterministic magnetic moment reversal, which includes: when a pulse current is applied along the channel direction, the error of the anomalous Hall resistance reversal signal observed by the Hall detectors arranged in the first region and the second region relative to the average value of the anomalous Hall resistance reversal signal observed by each Hall detector is within ±5%.

7. The two-dimensional heterojunction device according to claim 1, characterized in that, It also includes a protective layer that at least covers the upper surface of the two-dimensional antiferromagnetic layer, and the protective layer is made of hexagonal boron nitride material.

8. The two-dimensional heterojunction device according to claim 1, characterized in that, The anomalous Hall resistor flip signal is the flip ratio and the critical flip current density.

9. A method for fabricating a two-dimensional heterojunction device according to any one of claims 1 to 8, characterized in that, include: Fabricating metal electrodes on a substrate; The Fe3GaTe2 material is transferred onto the metal electrode to cover the channel region, forming the two-dimensional ferromagnetic layer. The CrSBr material is transferred to a local area on the surface of the Fe3GaTe2 material to form the two-dimensional antiferromagnetic layer; thus, the two-dimensional heterojunction device can be obtained.

10. A verification method for global field-free flipping of a two-dimensional heterojunction device according to any one of claims 1-8, characterized in that, include: Under zero external magnetic field conditions, a pulsed current is applied along the channel direction, and during the process, the anomalous Hall resistance of the Hall detection terminal in the first region and the second region is measured simultaneously; If the anomalous Hall resistance reversal signals of the first region and the second region are consistent, it proves that the two-dimensional heterojunction device can achieve global field-free reversal.

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