A spintronic device based on a ferromagnetic metal / two-dimensional ferromagnetic half-metal heterostructure

Abstract

This invention discloses a spintronic device based on a ferromagnetic metal / two-dimensional ferromagnetic half-metal heterojunction, comprising a ferromagnetic metal electrode and a single-layer two-dimensional ferromagnetic half-metal material layer. The ferromagnetic metal is nickel (Ni) or cobalt (Co), and the two-dimensional ferromagnetic half-metal is ferrous halide FeX2, where X = Cl, Br, or I. The two electrodes can form a heterojunction through edge contact or top contact, achieving a spin injection efficiency close to 100%. Hexagonal boron nitride (FeCl2) is further introduced into the Ni and ferrous chloride (FeCl2) heterojunction structure. h Ni / FeCl2 / BN can be used as a two-dimensional tunneling barrier layer to construct Ni / FeCl2 / h A van der Waals magnetic tunnel junction device based on -BN / FeCl2 / Ni. This structure retains fully spin-polarized tunneling current in the parallel magnetization direction and significantly reduces transmittance in the antiparallel magnetization direction, achieving a tunnel magnetoresistance (TMR) exceeding 3000%. This invention achieves effective control of spin transport at the device level through heterojunction structure and interface configuration design, and is suitable for spin valves, spin filters, and low-power magnetic tunnel junction memories.

Description

Technical Field

[0001] This invention belongs to the field of spintronics technology and relates to a spintronic device based on a ferromagnetic metal / two-dimensional ferromagnetic half-metal heterojunction, which can realize high polarization spin injection and tunnel magnetoresistance modulation. Background Technology

[0002] Spintronics is a novel technology that utilizes the electron spin degree of freedom for information transmission and processing. Unlike traditional electronics that use charge as a carrier, spintronic devices can simultaneously achieve low power consumption, high speed, and non-volatile storage functions [Baibich MN, Broto JM, Fert A, et al. Giant Magnetoresistance of (001)Fe / (001)Cr Magnetic Superlattices [J]. Physical Review Letters, 1988, 61(21):2472-2475.]. Among them, spin filters and magnetic tunnel junctions (MTJs) are the core structures for realizing spin-selective transport and logic operations. Their performance mainly depends on spin polarization, spin retention time, and interface transport characteristics.

[0003] Traditional MTJ devices typically employ a multilayer structure of metal / insulator / metal, such as cobalt (Co) / magnesium oxide (MgO) / Co or iron (Fe) / MgO / Fe systems, which achieve the magnetoresistive effect through spin-related tunneling. However, these devices suffer from conductivity mismatch, strong interface scattering, and complex fabrication processes, leading to limited spin injection efficiency [Schmidt G, Ferrand D, Molenkamp LW, et al. Fundamental obstacle for electrical spin injection from a ferromagnetic metal into a diffusive semiconductor [J]. Physical Review B, 2000, 62(8): R4790-R4793.]. Furthermore, chemical reactions and interface roughness in multilayer films often cause spin polarization losses, affecting device reliability.

[0004] With the rise of two-dimensional materials, spintronics has ushered in new development opportunities. Since the successful exfoliation of graphene in 2004, two-dimensional transition metal chalcogenides (TMDs), black phosphorus, and hexagonal boron nitride (…) have seen significant advancements in spintronics. hSystems such as chromium triiodide (CrI3) and iron germanium tellurium (Fe3GeTe2) have been extensively studied [Novoselov KS, Geim AK, Morozov SV, et al. Electric Field Effect in Atomically Thin Carbon Films [J]. Science, 2004, 306(5696): 666-669.]. In particular, the discovery of intrinsic two-dimensional ferromagnetic materials such as chromium triiodide (CrI3) and iron germanium tellurium (Fe3GeTe2) in 2017 verified the stable ferromagnetic order at a single atomic layer thickness, providing a new platform for the construction of two-dimensional spin valves and magnetic tunnel junctions [Gong C, Li L, Li Z, et al. Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals [J]. Nature, 2017, 546(7657): 265-269.].

[0005] However, it should be noted that the intrinsic spin polarization characteristics of a material are not directly equivalent to the spin transport effect at the device level. In practical devices, factors such as the contact mode between the two-dimensional ferromagnetic half-metal material and the metal electrode, the interface coupling form, and the interface state distribution all significantly affect the spin transport behavior. An unreasonable contact configuration may introduce orbital hybridization, interface state leakage, or spin scattering, thereby weakening the device manifestation effect of the intrinsic spin polarization characteristics of the material. Therefore, how to effectively control the spin transport characteristics of two-dimensional ferromagnetic half-metals at the device level through reasonable heterojunction structure design still needs further research and improvement [Yang HX, Hallal A, Terrade D, et al. ProximityEffects Induced in Graphene by Magnetic Insulators: First-PrinciplesCalculations on Spin Filtering and Exchange-Splitting Gaps [J]. PhysicalReview Letters, 2013, 110(4): 046603.].

[0006] Based on the above background, this invention proposes a heterojunction system based on a ferromagnetic metal and a two-dimensional ferromagnetic half-metal—a single-layer iron halide (FeX2, where X = Cl, Br, I). Theoretical calculations have shown that this system can achieve a near 100% spin-down transmission probability near the Fermi level, while significantly suppressing the spin-up channel. Specifically, the FeX2 material exhibits spin-dependent transport characteristics under the interface modulation of the heterojunction. The spin-down band is metallic at the Fermi level, while the spin-up band has a band gap, thus exhibiting high conductivity for spin-down electrons near the Fermi level and effectively blocking the transmission of spin-up electrons. This heterojunction spin filtering structure can achieve excellent spin filtering capabilities, and by optimizing the material and structural configuration, the spin injection efficiency can be significantly improved. Furthermore, this invention proposes to introduce... h -BN as a tunneling barrier in MTJ device structure h -BN exhibits excellent insulation and a smooth surface, effectively improving tunnel magnetoresistance (TMR) and reducing spin scattering, further enhancing the device's chemical stability and performance robustness. The spin filter and magnetic tunnel junction device of this invention possess simple structure, high integration, and excellent performance, effectively overcoming the shortcomings of traditional spintronic devices in spin injection efficiency and interface stability. This provides a new solution for the design and application of future low-power spin logic devices and spin memories. Summary of the Invention

[0007] To address the problems of conductivity mismatch, Fermi level pinning, low spin polarization efficiency, and difficulty in controlling interfacial chemical reactions at the interface between ferromagnetic metals and semiconductors or two-dimensional materials in existing technologies, this invention aims to propose a spintronic device with a simple structure, stable interface, high spin selectivity, and low power consumption. This is achieved by constructing a coupled heterojunction based on a ferromagnetic metal (nickel or cobalt) and a two-dimensional ferromagnetic half-metal FeX2, or by introducing further... h -BN forms a van der Waals coupled MTJ structure, thereby enabling efficient spin filtering, spin injection or TMR control, providing a feasible device platform for spin valves, magnetic tunnel junctions and low-power spin devices.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] (a) Ferromagnetic metal / two-dimensional ferromagnetic semimetal heterojunction spin filter structure

[0010] This invention proposes a spintronic device comprising a heterojunction spin filter structure composed of a ferromagnetic metal and a single layer of two-dimensional ferromagnetic half-metal FeX2. FeX2 exhibits typical ferromagnetic half-metallic properties: its spin-down band exhibits metallicity at the Fermi level, while its spin-up band has a band gap. Therefore, in the vicinity of the Fermi level, selective transmission of spin-down electrons and significant suppression of spin-up electrons can be achieved in the heterojunction structure.

[0011] The ferromagnetic metal electrode can be selected from nickel (Ni) or cobalt, and can form two configurations with FeX2:

[0012] ①Edge-contact lateral heterojunction (lateral spin filter structure): Electrons are transported along the planar direction, the contact interface resistance is small, and higher initial spin injection efficiency can be obtained. It is suitable for planar structures such as spin valves.

[0013] ② Vertical heterojunction with top contact (vertical spin filter structure): Ferromagnetic metal forms a vertical contact with the FeX2 layer through the van der Waals gap, without chemical bond reaction, and the interface is highly clean, which is suitable for vertical spin injection structure.

[0014] Based on density functional theory (DFT) and non-equilibrium Green's function (NEGF) spin transport calculations, the following results are obtained: ① All Ni / FeX2 and Co / FeX2 systems can achieve nearly 100% spin-down transmittance near the Fermi level, and spin-up electron transmittance is close to 0; ② The vertical heterojunction spin filter structure formed by Ni / FeCl2 can obtain higher down-spin polarization conductance; ③ When FeI2 material is used as the two-dimensional ferromagnetic half-metal, the vertical heterojunction spin filter structure formed has the lowest spin-state reversal energy, and the corresponding spin polarization reversal voltage is less than 0.5 V, which is suitable for low-power applications; ④ Although the edge contact structure has relatively higher down-spin conductance, the top contact structure has better interface stability and integration area. The ferromagnetic metal and FeX2 two-dimensional ferromagnetic half-metal heterojunction proposed in this invention can overcome the bottleneck of low spin injection efficiency of traditional ferromagnetic metal electrodes.

[0015] (ii) Magnetic tunnel junction structure based on ferromagnetic metal / two-dimensional ferromagnetic half-metal heterostructure

[0016] Based on (I), this invention also designs an MTJ device structure, which includes, from top to bottom, the following sequentially stacked components: a ferromagnetic metal upper electrode, a first layer of two-dimensional ferromagnetic half-metal material, a tunneling barrier layer, a second layer of two-dimensional ferromagnetic half-metal material, and a ferromagnetic metal lower electrode. The ferromagnetic metal upper and lower electrodes are both made of the same ferromagnetic metal (Ni or Co). The first and second layers of two-dimensional ferromagnetic half-metal material are both selected from monolayer FeX2 (X = Cl, Br, I). The tunneling barrier layer is a single layer or three layers. h -BN. For example, from Ni / FeCl2 / h A vertically symmetric MTJ composed of BN / FeCl2 / Ni. The above MTJ structure has the following characteristics: ① Spin polarization is generated by the ferromagnetic metal electrode; ② FeX2 acts as a spin filter layer, exhibiting spin half-metallicity, enabling single-spin selective implantation; ③ h -BN, as a tunneling barrier, has the properties of wide bandwidth and controllable number of layers, which can effectively regulate the spin channel resistance matching and tunneling efficiency.

[0017] Transport calculations under both parallel (P) and antiparallel (AP) ferromagnetic electrode magnetization configurations show that: ① the spin-down channel exhibits a significant transmission peak near the Fermi level, while transmission through the upper spin channel is significantly suppressed; ② in the configuration of parallel magnetization directions, the spin polarization of the lower spin in the MTJ structure is close to 100%; ③ monolayer h The theoretical TMR of the device under the -BN barrier can reach 10 at zero bias. 5 %; ④ Three-story h Although -BN reduces transmittance, it still maintains a stable tunnel magnetoresistance of over 3000% under a bias voltage of 0.1 V.

[0018] The spintronic device and the MTJ structure proposed in this invention can both be applied to non-volatile memory cells and corresponding memory devices.

[0019] Compared with existing technologies, the advantages of this invention are as follows: By constructing a heterojunction structure between a ferromagnetic metal and a two-dimensional ferromagnetic half-metal and designing the contact method and interface coupling form, effective control of spin transport behavior is achieved at the device level, enabling electrons with different spin orientations to exhibit significantly different transmission characteristics at the interface; this invention also provides two heterojunction structure forms, edge contact and top contact, which can flexibly design lateral or vertical spin transport paths according to different device requirements, expanding the applicable scenarios of the device; compared with traditional Co / MgO series MTJs, the MTJ structure of this invention reduces the adverse effects of interface orbital hybridization and interface defect states on spin transport by adopting a van der Waals coupling interface, thereby improving the device's operational stability; and the introduction of two-dimensional... h The addition of a -BN insulating barrier layer further enhances spin-selective tunneling characteristics, and the balance between device performance and stability can be optimized by adjusting the barrier layer thickness. The device described in this invention has a simple structure, is easily compatible with existing two-dimensional material device fabrication and integration processes, and possesses good engineering implementation potential; it is suitable for applications such as non-volatile spin memory and low-power spin logic.

[0020] It should be noted that the technical solution proposed in this invention focuses on the design of heterojunction structures and the realization of their spin-selective transport mechanism. Those skilled in the art can achieve the corresponding working conditions through materials engineering, strain or external field control methods according to specific application requirements. Attached Figure Description

[0021] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0022] Figure 1 The diagram shows a heterojunction structure composed of a three-dimensional ferromagnetic metal (Co or Ni) and a single layer of two-dimensional FeX2. (a) is a lateral heterojunction with edge contact, and (b) is a vertical heterojunction with top contact. The pink atoms are three-dimensional ferromagnetic metal atoms, the orange atoms are iron (Fe) atoms, and the green atoms represent halogen element X (X = Cl / Br / I) atoms.

[0023] Figure 2 This is a schematic diagram of the atomic structure of a single layer of FeX2, where orange atoms are iron (Fe) atoms and green atoms are halogen elements X (X = Cl / Br / I) atoms.

[0024] Figure 3 The diagram shows the band structure of a single-layer ferrous halide and its corresponding density of states (DOS). (a) represents FeCl2, (b) represents FeBr2, and (c) represents FeI2. Blue and red represent spin-up and spin-down states, respectively.

[0025] Figure 4 The values ​​represent the spin-up (blue) and spin-down (red) transmittance of Ni and different types of heterojunctions of monolayer two-dimensional FeX2, where the Fermi energies of the left and right sides of the heterojunction are aligned to 0 eV: (a) Ni / FeCl2 edge contact; (b) Ni / FeBr2 edge contact; (c) Ni / FeI2 edge contact; (d) Ni / FeCl2 top contact; (e) Ni / FeBr2 top contact; (f) Ni / FeI2 top contact.

[0026] Figure 5 The values ​​represent the spin-up (blue) and spin-down (red) transmittance of different types of heterojunctions of Co and monolayer two-dimensional FeX2, where the Fermi energies of the left and right sides of the heterojunction are aligned to 0 eV: (a) Co / FeCl2 edge contact; (b) Co / FeBr2 edge contact; (c) Co / FeI2 edge contact; (d) Co / FeCl2 top contact; (e) Co / FeBr2 top contact; (f) Co / FeI2 top contact.

[0027] Figure 6 For Ni / FeCl2 / x layer h -Schematic diagram of a BN / FeCl2 / Ni magnetic tunnel junction device. Green atoms represent Ni, blue atoms represent boron (B) atoms, and pink atoms represent nitrogen (N) atoms.

[0028] Figure 7 Under no bias voltage conditions, Figure 6 The schematic diagram of the spin transmission spectrum of the MTJ structure shown is illustrated with the ferromagnetic electrodes arranged in parallel (P) and antiparallel (AP) magnetization directions: (a) monolayer h -BN barrier, parallel configuration; (b) Single layer h -BN barrier, antiparallel configuration; (c) Three layers h -BN barrier, parallel configuration; (d) Three layers h -BN barrier, antiparallel configuration.

[0029] Figure 8 Under a bias voltage of 0.1V, Figure 6 The schematic diagrams of the spin transmission spectra of the MTJ structure shown are as follows: (a) Single layer h -BN barrier, parallel configuration; (b) Single layer h -BN barrier, antiparallel configuration; (c) Three layers h -BN barrier, parallel configuration; (d) Three layers h -BN barrier, antiparallel configuration.

[0030] Figure 9 Under no bias and 0.1V bias voltage conditions, Figure 6 The MTJ structure shown has different numbers of layers. h -BN represents the TMR value in the case of a barrier layer. Detailed Implementation

[0031] The embodiments of the present invention will be further described below with reference to the accompanying drawings and first-principles DFT calculation results. Those skilled in the art can reproduce the present invention based on the following embodiments, but the present invention is not limited thereto. The technical features in each embodiment can be combined arbitrarily without conflict. The materials of each layer in the device of the present invention belong to known two-dimensional or metallic material systems and can be realized by existing methods such as thin film deposition, mechanical exfoliation, van der Waals transfer, or epitaxial growth; the preparation method does not constitute a limitation of the present invention.

[0032] Example 1: Edge-contact ferromagnetic metal / monolayer FeX2 transverse heterojunction spin filter

[0033] This embodiment provides an edge-contact spin filter based on a ferromagnetic metal / two-dimensional ferromagnetic half-metal lateral heterojunction. The device includes a ferromagnetic metal electrode and a two-dimensional ferromagnetic half-metal layer sequentially arranged. A lateral heterojunction is formed between the ferromagnetic metal electrode and the two-dimensional ferromagnetic half-metal layer through edge contact, thereby constructing a horizontal electron transport channel. Its structural schematic is shown below. Figure 1As shown in (a). The two-dimensional ferromagnetic half-metal material is selected from FeX2. Taking FeCl2 as an example, the atomic structure of a single layer of FeCl2 is as follows. Figure 2 As shown; this type of material exhibits typical ferromagnetic half-metallic properties. Its spin-down band exhibits metallic properties at the Fermi level, while its spin-up band has a significant band gap near the Fermi level. Its typical band structure is as follows: Figure 3 As shown.

[0034] In this embodiment, the electronic structure and transport properties of the device are calculated using the Synopsys Quantum Atomistic Toolkits software platform, employing a DFT combined with the NEGF method. The SGGA-PBE exchange-correlated functional is used in the calculations, and the pseudopotential and basis set are the FHI all-electron double-zeta polarized basis set, with an energy cutoff of 80 Hartree. To ensure calculation accuracy in the transport direction, k Point sampling was set to 3×1×218, with high-density sampling along the transport direction. Periodic boundary conditions, Neumann boundary conditions, and Dirichlet boundary conditions were applied in the transverse width direction, vertical direction, and transport direction, respectively. During structural optimization, the energy convergence accuracy was set to 10. -4 eV, the atomic force threshold is less than 0.01 eV / Å.

[0035] The corresponding spin-resolved transmission spectrum results are as follows Figure 4 (a)-(c) and Figure 5 As shown in (a)-(c), the calculation results show that when a ferromagnetic metal electrode forms a lateral heterojunction with a two-dimensional ferromagnetic half-metal material layer FeX2 via an edge contact, charge carriers are directly injected along the plane of the two-dimensional material. The spin-up electron channel is significantly suppressed near the Fermi level, while the spin-down electron channel maintains good conductivity. When Ni is used as the ferromagnetic metal electrode to form an edge-contact lateral heterojunction with FeCl2, under zero bias conditions, the spin-up resolved conductance is close to zero, while the spin-down resolved conductance is approximately 6.73 × 10⁻⁶. - 5 S; When the two-dimensional ferromagnetic half-metal material is replaced with FeBr2, the spin-down resolved conductivity is approximately 3.0 × 10⁻⁶. -5 S; however, when FeI2 is used, the spin-down resolved conductance is approximately 1.28 × 10⁻⁶. -5S. The above results demonstrate that the Ni / FeX2 edge-contact lateral heterojunction can achieve stable spin-down dominated transport in different halide systems. When Co is used as the ferromagnetic metal electrode, the resulting Co / FeX2 edge-contact lateral heterojunction also exhibits significant spin-selective transport characteristics. Specifically, the spin-up resolved conductance in the Co / FeCl2 edge-contact structure is close to zero, while the spin-down resolved conductance is approximately 2.69 × 10⁻⁶. -5 S; In the Co / FeBr2 structure, the spin-down resolved conductivity is approximately 3.91 × 10⁻⁶. -5 S; In the Co / FeI2 structure, the spin-down resolved conductivity is approximately 1.55 × 10⁻⁶. -5 S. The above results verify that the aforementioned lateral heterojunction structure can effectively suppress the spin-up channel and achieve high spin-polarization injection under different ferromagnetic metal electrode conditions. Near the Fermi level, the transmittance of the spin-down channel in the aforementioned edge-contact lateral heterojunction structure is close to 100%, while the spin-up channel is essentially closed, indicating that this structure can achieve extremely high spin-polarization injection efficiency. Therefore, the edge-contact lateral heterojunction described in this embodiment can serve as a high-efficiency spin filter, significantly improving spin-polarization injection and extraction efficiency, and is suitable for planar spin valves, spin logic, and memory devices.

[0036] Example 2: Top-contact ferromagnetic metal / monolayer FeX2 vertical heterojunction spin filter

[0037] This embodiment provides a top-contact vertical structure spin filter based on a ferromagnetic metal / two-dimensional ferromagnetic half-metal heterojunction. The device includes a ferromagnetic metal electrode and a two-dimensional ferromagnetic half-metal layer arranged sequentially. A vertical heterojunction is formed between the ferromagnetic metal electrode and the two-dimensional ferromagnetic half-metal layer through a top-contact method, as illustrated in the schematic diagram below. Figure 1 As shown in (b). The material selection, electronic structure of the materials, and spin transport properties calculation methods in this embodiment are the same as in Example 1, and will not be repeated here.

[0038] The corresponding spin-resolved transmission spectrum results are as follows Figure 4 (d)-(f) and Figure 5 As shown in (d)-(f). Calculation results show that when Ni is used as the ferromagnetic metal electrode and FeCl2 is used as the two-dimensional ferromagnetic half-metal layer to form a top-contact vertical heterojunction, the spin-down electron channel exhibits significant conductivity near the Fermi level, while the spin-up electron channel is almost completely closed. Specifically, under zero bias conditions, in the Ni / FeCl2 vertical heterojunction structure, the spin-up conductivity is close to zero, while the spin-down conductivity is approximately 5.7 × 10⁻⁶. -5 S, thus achieving a nearly complete spin-polarized current, such as Figure 4As shown in (d). Furthermore, when the two-dimensional ferromagnetic half-metal material is replaced by FeBr2 or FeI2, it still maintains significant spin-selective transport characteristics. Specifically, the spin-up conductivity in the Ni / FeBr2 vertical heterojunction is also close to zero, while the spin-down conductivity is approximately 2.61 × 10⁻⁶. -5 S, such as Figure 4 (e) Figure 4 In the FeI2 vertical heterojunction in (f), the spin-down conductivity is approximately 1.2 × 10⁻⁶. -5 S. When Co is used as the ferromagnetic metal electrode, the resulting Co / FeX2 top-contact vertical heterojunction also exhibits highly spin-selective transport behavior. Specifically, the spin-up conductance in the Co / FeCl2 vertical heterojunction is close to zero, while the spin-down conductance is approximately 5.29 × 10⁻⁶. -5 S, such as Figure 5 As shown in (d); Figure 5 The spin-down conductivity in the Co / FeBr2 structure of (e) is approximately 3.98 × 10⁻⁶. -5 S, and Figure 5 The spin-down conductivity in the Co / FeI2 structure of (f) is approximately 7.06 × 10⁻⁶. -6 S. The above results fully verify that the top-contact vertical heterojunction of ferromagnetic metal / two-dimensional ferromagnetic half-metal can effectively suppress spin-up channels and achieve high-polarization transport dominated by spin-down electrons under different material combinations. The conductivity values ​​indicate that the van der Waals gap at the heterojunction interface increases the resistance to spin injection. In addition, the calculation results also show that when Ni or Co is used to construct the top-contact vertical heterojunction with FeI2, the corresponding spin polarization reversal voltage is lower than 0.5 V, which is beneficial to achieve spin polarization reversal under lower bias conditions, thereby reducing the power consumption of the device and making it suitable for low-power spin manipulation applications. Compared with Example 1, the top-contact vertical heterojunction structure described in this embodiment improves interface stability while achieving efficient spin filtering. It has the advantages of simple structure and easy integration, and is suitable for devices such as magnetic tunnel junctions and spin-orbit moment (STT) magnetic memories.

[0039] Example 3: Single layer h -BN barrier magnetic tunnel junction structure

[0040] This embodiment provides a structure from top to bottom of Ni / FeCl2 / monolayer. hThe MTJ structure of -BN / FeCl2 / Ni was calculated using Synopsys Quantum ATK software using DFT and NEGF. An SGGA-PBE exchange-correlated functional was employed, with the pseudopotential and basis set being the FHI all-electron double-zeta polarized basis set. Grimme DFT-D3 van der Waals correction was introduced to accurately describe interlayer interactions, and the energy cutoff was set to 700 Rydberg to ensure computational accuracy in the transport direction. k Point sampling is set to 4×4×232, with periodic boundary conditions applied in the lateral and vertical directions, and Dirichlet boundary conditions applied in the transport direction. Energy convergence accuracy is 10. -4 Structural optimization was performed under conditions of eV and atomic interaction forces less than 0.01 eV / Å. Monolayer h The transmission spectrum of the -BN barrier MTJ structure calculated at zero bias (0 V) is as follows: Figure 7 As shown in (a) and (b), the results at a bias voltage of 0.1V are as follows: Figure 8 As shown in (a) and (b).

[0041] The results show that the MTJ structure exhibits significant spin-dependent transport characteristics under different ferromagnetic electrode magnetization configurations and bias conditions. Under zero bias conditions, when the magnetization configuration is in the parallel (P) state, the spin-up resolved conductance is approximately 1.76 × 10⁻⁶. -14 S, while the spin-down resolved conductance is approximately 4.90 × 10⁻⁶. -10 S, the total conductance is mainly contributed by the spin-down channel; when the magnetization is configured in an antiparallel (AP) state, the spin-up and spin-down resolved conductances are approximately 3.03 × 10⁻⁶. -13 S and 1.82×10 -13 S corresponds to a total conductance of approximately 4.85 × 10⁻⁶. -13 S. Due to the order-of-magnitude difference in conductance between parallel and antiparallel magnetization states, this structure can achieve a TMR as high as 100909% under zero bias conditions. Figure 9 Under a bias voltage of 0.1 V, a single layer h The -BN barrier MTJ still maintains a significant spin-selective transport characteristic. With the magnetization direction of the ferromagnetic electrode parallel, the spin-up resolved conductance is approximately 1.73 × 10⁻⁶. -14 S, spin-down resolved conductance is approximately 5.65 × 10⁻⁶. -11 S, the total conductance is mainly dominated by the spin-down channel; while in the antiparallel magnetization state of the ferromagnetic electrode, the spin-up and spin-down resolved conductances are approximately 8.47 × 10⁻⁶. -13 S and 7.16×10 -13 S corresponds to a total conductance of approximately 1.56 × 10⁻⁶. -12S. Under finite bias conditions, although the TMR value is lower than that under zero bias, it can still remain above 3500% ( Figure 9 The above results indicate that Ni / FeCl2 / monolayer h The MTJ structure composed of -BN / FeCl2 / Ni can maintain highly spin-asymmetric transport characteristics and exhibits good TMR, thus showing promising application prospects in low-power spin memory and logic devices.

[0042] Example 4: Three-layer h -BN barrier magnetic tunnel junction structure

[0043] This embodiment provides a Ni / FeCl2 / 3 layer from top to bottom. h -BN / FeCl2 / Ni MTJ device structure, in which the barrier layer h - The number of BN layers has increased from a single layer to three layers, and its structural diagram is as follows: Figure 6 As shown. The calculation method for the device structure is the same as in Example 3, and will not be repeated. Three layers h The transmission spectrum calculation results of the MTJ structure with -BN barrier at zero bias (0 V) are as follows: Figure 7 As shown in (c) and (d), the results at a bias voltage of 0.1V are as follows: Figure 8 As shown in (c) and (d).

[0044] Calculation results show that, with h Increasing the thickness of the -BN barrier reduces the overall transmittance of the spin-down channel, but still maintains a significant spin asymmetry. Under zero bias conditions: when the magnetization is configured in a parallel (P) state, the spin-up resolved conductance is approximately 1.97 × 10⁻⁶. -17 S, spin-down resolved conductance is approximately 4.70 × 10⁻⁶. -15 S, the total conductivity is approximately 4.72 × 10⁻⁶. - 15 S, the current is mainly contributed by the spin-down channel; when the magnetization is configured in an antiparallel (AP) state, the spin-up and spin-down resolved conductivities are approximately 6.70 × 10⁻⁶. -16 S and 6.64×10 -17 S corresponds to a total conductance of approximately 7.37 × 10⁻⁶. -16 S. Based on the above conductance values, the tunneling reluctance ratio of the MTJ structure under zero bias is approximately 540% ( Figure 9 When the bias voltage is 0.1 V and the magnetization is configured in the parallel (P) state, the spin-up resolved conductance is approximately 1.98 × 10⁻⁶. -17 S, spin-down resolved conductance is approximately 5.91 × 10⁻⁶. -14 S, the total conductivity is approximately 5.91 × 10⁻⁶. -14In the S; antiparallel (AP) magnetization configuration, the spin-up and spin-down resolved conductivities are approximately 1.78 × 10⁻⁶. -15 S and 6.65×10 -17 S, the total conductivity is approximately 1.85 × 10⁻⁶. -15 S. At an operating voltage of 0.1 V, the device's TMR value can be maintained at a relatively high level of around 3100%. Figure 9 Compared to single-layer h -BN barrier MTJ structure, three layers h -BN barriers improve the performance stability and breakdown resistance of devices after biasing by sacrificing some transmittance, making them suitable for spin memory device designs that require high robustness.

[0045] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A spintronic device, characterized in that, The heterojunction comprises a ferromagnetic metal electrode and a two-dimensional ferromagnetic half-metal material layer, wherein the ferromagnetic metal electrode is nickel (Ni) or cobalt (Co), and the two-dimensional ferromagnetic half-metal material is a monolayer of ferrous halide (FeX2), where X = Cl, Br, or I. The ferromagnetic metal electrode and the two-dimensional ferromagnetic half-metal material layer form a heterojunction interface through edge contact or top contact. The interface forms a selective spin transport channel, and electron spins with different orientations exhibit different transmission characteristics at the heterojunction interface.

2. The spintronic device according to claim 1, characterized in that, The heterojunction interface formed by the top contact method has a van der Waals gap between the ferromagnetic metal electrode and the two-dimensional ferromagnetic half-metal material layer, which can suppress interface orbital hybridization.

3. The spintronic device according to claim 1, characterized in that, The direction of spin-down in monolayer ferrous halide materials is determined by the spin polarization direction of the ferromagnetic metal electrode.

4. The spintronic device according to claim 1, characterized in that, The vertical spin filter structure formed by the top contact has a spin polarization reversal voltage of less than 0.5 V.

5. A magnetic tunnel junction, characterized in that, The structure, from top to bottom, consists of a ferromagnetic metal upper electrode (a), a first layer of two-dimensional ferromagnetic half-metal material (b), a tunneling barrier layer (c), a second layer of two-dimensional ferromagnetic half-metal material (d), and a ferromagnetic metal lower electrode (e), stacked sequentially. The ferromagnetic metal upper electrode (a) and the ferromagnetic metal lower electrode (e) are made of the same ferromagnetic metal, either Ni or Co. Both the first and second layers of two-dimensional ferromagnetic half-metal material (b) and d are selected from monolayer FeX2, where X = Cl, Br, or I. The tunneling barrier layer (c) is a monolayer to a trilayer of hexagonal boron nitride. h -BN.

6. The magnetic tunnel junction according to claim 5, characterized in that, The magnetic tunnel junction consists of sequentially stacked nickel / monolayer ferrous chloride (FeCl2) / monolayer to three-layer structures. h Composed of BN / monolayer FeCl2 / nickel.

7. A non-volatile memory cell, characterized in that, It contains a spintronic device as described in any one of claims 1 to 4 or a magnetic tunnel junction as described in any one of claims 5 to 6.

8. A storage device, characterized in that, It contains the storage unit as described in claim 7.

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