Torque Devices Research Articles

Ultralow Electric Current-Assisted Magnetization Switching due to Thermally Engineered Magnetic Anisotropy.

Control of magnetic anisotropy in thin films with perpendicular magnetic anisotropy is of paramount importance for the development of spintronics with ultralow-energy consumption and high density. Traditional magnetoelectric heterostructures utilized the synergistic effect of piezoelectricity and magnetostriction to realize the electric field control of magnetic anisotropy, resulting in additional fabrication and modulation processes and a complicated device architecture. Here, we have systematically investigated the electric current tuning of the magnetic properties of the metallic NiCo2O4 film with intrinsic perpendicular magnetic anisotropy. Ferrimagnetic-to-paramagnetic phase transition has been induced through Joule heating, resulting in a rapid decrease of both magnetic coercivity and moment. An ultralow current density of 2.5 × 104 A/cm2, which is 2 to 3 orders magnitude lower than that of conventional spin transfer torque devices, has been verified to be effective for the control of the magnetic anisotropy of NiCo2O4. Successful triggering of magnetic switching has been realized through the application of a current pulse. These findings provide new perspectives toward the electric control of magnetic anisotropy and design of spintronics with an ultralow driving current density.

Bilateral External Torque CT Reliably Detects Syndesmotic Lesions in an Experimental Cadaveric Study.

If tibiofibular syndesmotic injury is undetected, chronic instability may lead to persistent pain and osteoarthritis. So far, no reliable diagnostic method has been available. The primary objectives of this study were to determine whether defined lesions of the syndesmosis can be correlated with specific tibiofibular joint displacements caused by external rotational torque and to compare the performance of bilateral external torque computed tomography (BET-CT) and arthroscopy. Secondary objectives included an evaluation of the reliability of CT measurements and the suitability of the healthy contralateral ankle as a reference. Seven pairs of healthy, cadaveric lower legs were tested and assigned to 2 groups: (1) supination-external rotation (SER) and (2) pronation-external rotation (PER). In the intact state and after each surgical step, an ankle arthroscopy and 3 CT scans were performed. During the scans, the specimens were placed in an external torque device with 2.5, 5.0, and 7.5 Nm of torque applied. The arthroscopic and CT parameters showed significant correlations in all pairwise comparisons. The receiver operating characteristic (ROC) curve analyses yielded the best prediction of syndesmotic instability with the anterior tibiofibular distance on CT, with a sensitivity of 84.1% and a specificity of 95.2% (area under the curve [AUC], 94.8%; 95% confidence interval [CI], 0.916 to 0.979; p < 0.0001) and with the middle tibiofibular distance on arthroscopy, with a sensitivity of 76.2% and specificity of 92.3% (AUC, 91.2%; 95% CI, 0.837 to 0.987; p < 0.0001). Higher torque amounts increased the rate of true-positive results. BET-CT reliably detects experimental syndesmotic rotational instability, compared with the healthy side, with greater sensitivity and similar specificity compared with the arthroscopic lateral hook test. Translation of these experimental findings to clinical practice remains to be established. Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

A Case of Winching technique: A practical approach for insuperable chronicaly occluded indwelling iliac venous stents

Chronic iliac vein occlusions and post-thrombotic syndrome (PTS) are the major sources of life affecting symptomatic iliocaval venous obstruction contributing to the morbidity of chronic venous insufficiency and venous hypertension. Venous stenting is a treatment option for the management of PTS. Despite dedicated venous recanalization technologies, long-term patency rates of venous stents are still a matter of debate. Beside that, salvage of an occluded stent could be problematic or even impossible. It may be challenging to advance the balloon catheter distally to the occlusion, even after the lesion has been crossed with a guide wire. Here we describe a new technique for overcoming such difficult bottlenecks. In a supine patient, despite successful wire-recanalization of the vena cava, achieved after a popliteal access, the balloon catheter could not be passed through an occluded iliac vein stent and towards the vena cava. Consequently, the tip of the 260 cm wire, was retrieved with a snare from the vena cava and externalized through sheath inserted in the right jugular vein. Two separate balloon catheters were loaded over the two ends of the through and through guide wire and torque devices were used to lock at their exit ports. Occluded segments were afterwards crossed with the novel ‘Winching technique’ by pulling the balloon catheter instead of pushing it. We believe that this technique can speed up and facilitate the procedure for the occlusions that can be laborious to reanalyze by conventional methods.

Ion irradiation modulated magnetic properties of materials and its applications

Ion irradiation, a technology in which ion beams are used to irradiate materials, has high manipulation precision, short processing time, and many applications in the fields of material modification, chip manufacturing, biomedicine, energy and chemicals. Especially in magnetic material modification, customized modifications of magnetic materials can be achieved by precisely controlling the energy, dose, and direction of the ion beam. To further enhance the performances of magnetic materials and explore new magnetic devices, this study focuses on how ion irradiation precisely modulates various magnetic interactions and the analysis of its influence on the spin Hall effect and magnetic structural dynamics. Firstly, the latest research achievements are emphasized of ion irradiation regulated magnetic characteristics such as perpendicular magnetic anisotropy, exchange bias, and RKKY interaction. These regulation methods are crucial for understanding and optimizing the microstructure and properties of magnetic materials. Secondly, the significant role played by ion irradiation in regulating spin-orbit torque devices is discussed in detail. These applications demonstrate the potential of ion irradiation technology in designing high-performance magnetic storage and processing devices. Finally, the future applications of ion irradiation technology in the preparation of multifunctional magnetic sensors and magnetic media for information storage are discussed, highlighting its great enormous innovation and application potential in the field of magnetic materials.

Spintronic devices based on topological and two-dimensional materials

Novel quantum materials such as topological materials, two-dimensional materials, create new opportunities for the spintronic devices. These materials can improve the charge-spin conversion efficiency, provide high-quality interface, and enhance the energy efficiency for spintronic devices. In addition, they have rich interactions and coupling effects, which provides a perfect platform for finding new physics and novel methods to control the spintronic properties. Many inspiring results have been reported regarding the research on topological materials and two-dimensional materials, especially the layered topological and two-dimensional magnetic materials, and their heterostructures. This paper reviews the recent achievements of these novel quantum materials on spintronic applications. Firstly the breakthroughs that topological materials have been made in spin-orbit torque devices is introduced, then two-dimensional magnetic materials and their performances in spintronic devices are presented, finally the research progress of topological materials/two-dimensional magnetic materials heterostructures is discussed. This review can help to get a comprehensive understanding of the development of these novel quantum materials in the field of spintronics and inspire new ideas of research on these novel materials.

Voltage-Controlled Spin-Orbit-Torque-Based Nonvolatile Flip-Flop Designs for Ultra-Low-Power Applications

Flip-flop (FF) serves as a fundamental unit in various sequential logic circuits and complex digital electronic systems for generating, transforming, and temporarily storing digital signals. Nonvolatility plays a crucial role in FFs by ensuring instant data recovery after unexpected data loss. Nonvolatile flip-flop can quickly recover in a self-powered environment, making it suitable for application environments such as the Internet of Things (IOT). Unfortunately, most existing nonvolatile FFs (NVFFs) suffer from extended delays and high energy consumption during data backup and restore operations. In this paper, we propose two innovative voltage-controlled nonvolatile FFs (VC-FFs), namely VC-DFF (voltage-controlled D-FF) and VC-SRFF (voltage-controlled SR-FF), which address these challenges using voltage-controlled spin-orbit torque (VC-SOT) devices. The proposed designs are evaluated using a 40 nm CMOS process. Simulation results demonstrate that the proposed designs achieve significant improvements in write (recovery) energy consumption, with over 7.2× (1.54×) and 18.7× (2×) enhancements compared to their STT- and SOT-based counterparts, respectively.

Field‐Free Switching of Spin Crossbar Arrays by Asymmetric Spin Current Gradient

AbstractSpin orbit torque (SOT) devices with the advantages of high speed, low power consumption, and high stability have wide application prospects in the field of spintronics. The SOT‐based crossbar array device is an important extension of SOT devices, but it is not reported so far. Here, the all electrical magnetization switching of Hall crossings based on SOT crossbar array devices is realized. Through analyzing the current distribution and micromagnetic simulations, it is found that this field‐free SOT switching in the array devices comes from the asymmetric current density gradient distribution at the Hall‐crossings due to the shunt effect of grid circuits. All electrical tristate magnetization switching and the write protection of spin crossbar array devices are demonstrated. This work will further promote the application of the efficient memory or edge computing based on spin crossbar array devices.

Wafer‐Scale Epitaxial Growth of the Thickness‐Controllable Van Der Waals Ferromagnet CrTe2 for Reliable Magnetic Memory Applications

AbstractTo harness the intriguing properties of 2D van der Waals (vdW) ferromagnets (FMs) for versatile applications, the key challenge lies in the reliable material synthesis for scalable device production. Here, the epitaxial growth of single‐crystalline 1T‐CrTe2 thin films on 2‐inch sapphire substrates are demonstrated. Benefiting from the uniform surface energy of the dangling bond‐free Al2O3(0001) surface, the layer‐by‐layer vdW growth mode is observed right from the initial growth stage, which warrants precise control of the sample thickness beyond three monolayer and homogeneous surface morphology across the entire wafer. Moreover, the presence of the Coulomb interaction at the CrTe2/Al2O3 interface plays an important role in tailoring the anomalous Hall response, and the structural optimization of the CrTe2‐based spin‐orbit torque device leads to a substantial switching power reduction by 54%. The results may lay out a general framework for the design of energy‐efficient spintronics based on configurable vdW FMs.

Voltage-gated field-free spin–orbit torque switching in Pt/Co/Ir/MgO wedged structures

The ability to efficiently manipulate magnetization is of great significance for practical applications of spin–orbit torque (SOT) devices. In this study, we report the voltage-controlled, field-free SOT switching in perpendicular magnetized Pt/Co/Ir/MgO structures with wedge iridium interlayers. The insertion of a thin iridium interlayer at ferromagnet/oxide can significantly reduce the perpendicular magnetic anisotropy depending on the Ir thickness. The wedging of the iridium layer breaks lateral structural symmetry, resulting in deterministic switching without the assistance of in-plane magnetic fields. In such a structure, the SOT critical switching currents are remarkably decreased by 29% when a positive 6 V gate voltage is applied. Further quantitative analysis shows that multiple factors contribute to the decrease in switching currents, including a 23% reduction in magnetic anisotropy energy, a reduction in nucleation field, and a minor enhancement in damping-like torque under gate voltage. Moreover, the probabilistic hindrance that gate voltage poses to field-free switching is revealed by the decrease in current-induced perpendicular effective fields from symmetry-breaking. Our research shows that energy-efficient SOT switching can be controlled by gating and offers insight into the mechanism behind voltage-gated SOT switching.

Robust negative longitudinal magnetoresistance and spin–orbit torque in sputtered Pt3Sn and Pt3SnxFe1-x topological semimetal

Contrary to topological insulators, topological semimetals possess a nontrivial chiral anomaly that leads to negative magnetoresistance and are hosts to both conductive bulk states and topological surface states with intriguing transport properties for spintronics. Here, we fabricate highly-ordered metallic Pt3Sn and Pt3SnxFe1-x thin films via sputtering technology. Systematic angular dependence (both in-plane and out-of-plane) study of magnetoresistance presents surprisingly robust quadratic and linear negative longitudinal magnetoresistance features for Pt3Sn and Pt3SnxFe1-x, respectively. We attribute the anomalous negative longitudinal magnetoresistance to the type-II Dirac semimetal phase (pristine Pt3Sn) and/or the formation of tunable Weyl semimetal phases through symmetry breaking processes, such as magnetic-atom doping, as confirmed by first-principles calculations. Furthermore, Pt3Sn and Pt3SnxFe1-x show the promising performance for facilitating the development of advanced spin-orbit torque devices. These results extend our understanding of chiral anomaly of topological semimetals and can pave the way for exploring novel topological materials for spintronic devices.

Optical Verification of Physically Unclonable Function Devices Based on Spin‐Orbit Torque Switching

AbstractPhysically unclonable functions (PUFs) are used for various applications such as anticounterfeiting, authentication, and secret key generation. They are generally evaluated through electrical measurements, requiring much time and effort due to the many electrical connections required. This study proposes an optical verification of spin‐orbit torque (SOT) devices for PUF design. SOT devices have gained much attention because they resist degradation and thermal changes and can generate secret keys with high reproducibility. A simple optical method based on the magneto‐optical Kerr effect is introduced to verify the authenticity of the proposed SOT PUF device. Furthermore, this study assesses the feasibility of using a W/CoFeB/MgO/Ta structure as a PUF. The 24‐bit device shows a reliability of 97.8 ± 1.03%, making it a promising candidate for use as a spintronics‐based PUFs.

High-throughput screening giant bulk spin-split materials

Current-induced spin polarization or electric-field-controlled energy splitting shows great potential in the application of spintronic devices, such as spin–orbit torque devices, spin transistors, and so on. These mechanisms are often found in spin-split materials with strong spin-orbital coupling (SOC), which jointly trigger the Rashba, Dresselhaus, or Zeeman effect. The essential criterion to evaluate the strength of SOC is the spin-split energy. Thus, searching for bulk materials with large spin-split energy has attracted great interest. In this work, a high-throughput workflow was designed with the proposed three-point-spin-texture method, and 440 Rashba, 411 Dresselhaus, and 469 Zeeman-type candidate materials with large spin-split energy were screened out. Moreover, the spin-split energy of Rashba material KSnSb, Dresselhaus material TaSi2, and Zeeman-type material PtN2 achieve 0.19 eV, 0.82 eV, and 0.55 eV, respectively. This work significantly expands the materials database for spintronic devices and paves the way for further experimental research.

An in vitro study evaluating the efficacy of a novel mount with torque control designed to tighten Osstell® transducers.

To evaluate the efficacy of a novel mount with torque control for tightening of Osstell® transducers and to determine the reliability of recorded ISQ measurements from implants placed in various bone densities. MATERIALAND METHODS: Fifty-six implants, comprising seven different implant types, were placed in eightpolyurethane blocks representing D1, D2, D3, and D4 bone densities. Resonance frequency analysis (RFA) transducers were attached to each implant in four different ways: (a) hand tightening, (b) hand tightening with a SmartPeg Mount™, (c) hand tightening using the novel mount with torque control (SafeMount) and (d) tightening to 6 Ncm with a calibrated torque device. ISQ measurements were taken and a second operator repeated the measurements. Intraclass correlation coefficient (ICC) was calculated to assess the reliability of the measurements and linear mixed effects regression was employed to determine the effect explanatory variables had on ISQ values. There was a statistically significant difference in ISQ values obtained by hand tightening transducers compared to the calibrated torque device p < .001, 95%(-2.89, -1.21) but not between any other tightening methods. There was excellent agreement between the two RFA devices (ICC 0.986) and between buccal and mesial measurements (ICC 0.977). For all transducer tightening methods there was excellent inter-operator agreement in D1 and D2 (ICC > 0.8) but very poor agreement in D4 (ICC < 0.24). Bone density accounted for 36% of the variation in ISQ values, the implant for 11% and the operator for 6%. SafeMount, did not significantly improve the reliability of the RFA measurements when compared to the standard mount, but calibrated torque devices seem to have benefits when compared to tightening the transducers by hand. Results also indicate that the ISQ values should be interpreted with caution when measuring implant stability in poor quality bone regardless of the implant geometry.

Origin of the anomalous Hall effect at the magnetic insulator/heavy metals interface

Ferrimagnetic insulators (FIMIs) are considered to be promising candidates in spin–orbit torque (SOT) devices due to their ability to propagate a spin current by magnons without Ohmic losses owing to the absence of electronic scattering. Moreover, any electrical current shunt is avoided in magnetic insulating materials. On the other hand, SOT-induced magnetization switching is generally measured through the anomalous Hall effect (AHE) in FIMI/heavy metal (HM) systems. However, the origin of AHE in FIMI/HM remains elusive since charges flow only in the HM. Here, we experimentally demonstrate that the AHE has the same origin as the spin Hall magnetoresistance (SMR). To this end, we have studied two bilayer heterostructures, Tm3Fe5O12(TmIG)/W and TmIG/Pt, where we ensure opposite spin Hall effect (SHE) signs for two heavy metals (W and Pt). The magnitudes of AHE and SMR are found to be larger for TmIG/W than TmIG/Pt. We have also evidenced the identical polarity of AHE hysteresis in both systems revealing a square dependency on the spin Hall angle whereas the current-induced magnetization switching polarity in TmIG/W is opposite to that of TmIG/Pt as expected for opposite spin Hall angle signs. Our results establish that the AHE and the spin-Hall magnetoresistance in TmIG insulating ferromagnets and heavy metal bilayers originate from the same mechanism.

A Drift-Diffusion Based Modeling and Optimization Framework for Nanoscale Spin-Orbit Torque Devices

We present a comprehensive set of experimentally validated/calibrated models that capture the physics of the nanoscale spin-orbit torque (SOT) devices. We consider various effects that are prominent at nanoscale including incomplete current redistribution, interface spin mixing, and nonuniform resistivity that were ignored in the prior modeling efforts. We develop a formalism based on drift-diffusion equations and the transfer matrix method to accurately estimate spin current distribution. We utilize finite element simulations to accurately calculate electric current density and field, and see considerable differences to the results from the simplified lumped model commonly used. For example, we calculate ~20% smaller spin current in a 15-nm-wide ferromagnet with a 4-nm-thick <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -W SOT channel. We further account for the effect of interface scattering on resistivity. Finally, we quantify the optimal SOT-layer thickness that minimizes the write energy as a function of spin diffusion length and conductivity of SOT materials. We show that the optimal thickness increases with the spin diffusion length and decreases with the conductivity.

Perspectives on field-free spin–orbit torque devices for memory and computing applications

The emergence of embedded magnetic random-access memory (MRAM) and its integration in mainstream semiconductor manufacturing technology have created an unprecedented opportunity for engineering computing systems with improved performance, energy efficiency, lower cost, and unconventional computing capabilities. While the initial interest in the existing generation of MRAM—which is based on the spin-transfer torque (STT) effect in ferromagnetic tunnel junctions—was driven by its nonvolatile data retention and lower cost of integration compared to embedded Flash (eFlash), the focus of MRAM research and development efforts is increasingly shifting toward alternative write mechanisms (beyond STT) and new materials (beyond ferromagnets) in recent years. This has been driven by the need for better speed vs density and speed vs endurance trade-offs to make MRAM applicable to a wider range of memory markets, as well as to utilize the potential of MRAM in various unconventional computing architectures that utilize the physics of nanoscale magnets. In this Perspective, we offer an overview of spin–orbit torque (SOT) as one of these beyond-STT write mechanisms for the MRAM devices. We discuss, specifically, the progress in developing SOT-MRAM devices with perpendicular magnetization. Starting from basic symmetry considerations, we discuss the requirement for an in-plane bias magnetic field which has hindered progress in developing practical SOT-MRAM devices. We then discuss several approaches based on structural, magnetic, and chiral symmetry-breaking that have been explored to overcome this limitation and realize bias-field-free SOT-MRAM devices with perpendicular magnetization. We also review the corresponding material- and device-level challenges in each case. We then present a perspective of the potential of these devices for computing and security applications beyond their use in the conventional memory hierarchy.

Interfacial Engineering Strategies for Efficient Spin–Orbit Torque Devices with Pt Alloys

To make spin–orbit torque magnetic random-access memories (SOT-MRAMs) become competitive enough to replace the contemporary memory architecture, it is of great importance to utilize conductive SOT materials that possess large damping-like spin–orbit torque (DL-SOT) efficiencies and back-end-of-line (BEOL) compatibility. In this work, we report a BEOL-compatible CoFeB/MgO-based heterostructure with the Pt–Cr alloy as the spin current source (SCS) and inserted a Pt/Co/Pt composite layer to achieve texture decoupling and ferromagnetic coupling. A thermally robust perpendicular magnetic anisotropy (PMA) of the hybrid heterostructure can be retained after annealing at 400 °C for 1 h, while maintaining large DL-SOT efficiencies of the annealed Pt–Cr alloys (ξDL ∼ 0.34 for Pt0.70Cr0.30). Additionally, by optimizing the current distribution with a resistive Pt spacer layer, it is possible to simultaneously enhance the current-to-effective field conversion ratio (Hzeff/I) and retain the apparent ξDL (ξDL ∼ 0.37 for Pt0.79Cr0.21). Moreover, the critical switching current density can be reduced from JcPt ∼ 2.0 × 107 A·cm–2 for Pt to JcPt0.70Cr0.30 ∼ 4.9 × 106 A·cm–2 for Pt0.70Cr0.30 without tampering the thermal stability of the annealed heterostructure. These interfacial engineering strategies provide directions to integrate Pt-based SCSs with large ξDL into a BEOL-compatible platform for future SOT-MRAM devices with PMA.

Research progress of novel quantum states and charge-spin interconversion in transition metal oxides

For efficient storage and processing of massive data in the information technology era, spintronic device attracts tremendous attention due to its low power consumption and non-volatile feature. Spin source material, which can efficiently generates spin current, is an important constituent of novel spin-orbit torque device. The efficiency of spin current generation in spin source material directly determines the performances of various spintronic devices. In the past two decades, great progress has been made in exploring high-efficient spin source material systems and understanding the relevant physical mechanisms. A wide variety of materials are explored, ranging from traditional heavy metals and semiconductors to topological insulators and two-dimensional (2D) materials. Recently, the material family of transition metal oxides attracts tremendous attention due to its efficient and highly tunable charge-spin conversion intimately related to its emerging novel quantum states and electronic structure. The mechanism of charge-spin conversion generally has two contributions: the bulk spin Hall effect and the spin-momentum locked interface with inversion symmetry breaking. Novel electronic structures such as topological band structures and spin-momentum locked surface states can realize efficient charge-spin conversion. For example, the Weyl points in SrRuO&lt;sub&gt;3&lt;/sub&gt; and the topological Dirac nodal line in SrIrO&lt;sub&gt;3&lt;/sub&gt; are predicted to give rise to a large Berry curvature and corresponding spin Hall conductance; the topological surface states can generate spin accumulation due to spin-momentum locking; the Rashba states at the oxide interface such as the 2D electron gas in SrTiO&lt;sub&gt;3&lt;/sub&gt; and KTaO&lt;sub&gt;3&lt;/sub&gt; can generate spin current by Rashba-Edelstein effect. Furthermore, the entanglement of various degrees of freedom, including spin, charge, lattice and orbit in transition metal oxides lead to the electronic structure being highly tunable by various methods including gate voltage, substrate constraint, thickness, interface engineering, etc. Therefore, charge-spin conversion in transition metal oxides is of great significance for both modulating of novel electronic structure in fundamental research and exploring its promising potential in future spintronic devices. In this review, we focus on introducing aspects of exotic electronic structures, spin transport mechanism, charge-spin interconversion characterization, efficiency and manipulation in transition metal oxides, and giving a prospect on the future development trend.

Spin-orbit torque efficiency improved by BiSePt alloy

In order to achieve high-efficiency spin-orbit torque devices, higher charge-spin conversion efficiency, and lower resistivity are required in the strong spin-orbit coupling layer that provides the spin current. In this work we prepare BiSePt alloy/Co heterostructures with in-plane magnetic anisotropy by magnetron sputtering deposition. The alloy layer is deposited via one of two procedures, either co-sputtering or alternative-sputtering. We study the BiSePt alloy samples and find that the spin orbit torque (SOT) efficiency decreases with the increase of Pt component, which is attributed to the change of topological order of Bi&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; amorphous surface, caused by Pt doping. And the resistivity decreases with the increase of Pt component, which depends on the increase of metallic property. Due to the balance of these two competing mechanisms, the spin Hall conductivity of the alloy layer varies non-monotonically with the concentration ratio, and reach an optimal value at a ratio of 67% of Bi&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; component. With the increase of the Bi&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt; component, the SOT efficiency, electrical resistivity and spin Hall conductance of the alloy layer show different trends. At about 20%–70%, they increase/decrease tardily. At about 70%–100%, the resistivity ascends more prominently than the SOT efficiency, which leads the spin Hall conductance to decrease. Comparing with using the co-sputtering deposition, the electrical conductivity and spin Hall angle of the alloy layer obtained using alternating sputtering deposition are small, which is attributed to the enhancing of interfacial scattering and the filter effect of Pt on the spin flow. In contrast to traditional pure heavy metal materials (such as Pt, Ta) and topological insulator materials like Bi&lt;sub&gt;2&lt;/sub&gt;Se&lt;sub&gt;3&lt;/sub&gt;, our BiSePt alloy devices obtained by co-sputtering deposition achieve industry-matched preparation conditions, greater SOT efficiency, and considerable electrical conductivity of the alloy layer, thus making further applications of SOT devices possible.

Analysis of spin-orbit torque magnetic tunnel junction model without external magnetic field assistance based on antiferromagnetism

The effect of spin-orbit torque (SOT) provides a new method of implementing ultra-low power spintronic devices. The in-plane exchange bias (EB) field in antiferromagnetic material can effectively assist SOT magnetization switching. Meanwhile, the utilization of voltage-controlled magnetic anisotropy (VCMA) can effectively reduce the switching barrier. Taking advantage of the EB and VCMA effect, it is possible to realize SOT magnetic tunnel junctions without external field assistance. In this work, a spin-orbit torque magnetic tunnel junction model composed of antiferromagnetic/ferromagnetism/oxides without external magnetic field is developed by solving the modified Landau-Lifshitz-Gilbert (LLG) modular equation, and its magnetization dynamics is analyzed and studied. The effective fields in the model include the demagnetization field, thermal noise field, perpendicular magnetic anisotropy field with VCMA effect, and exchange bias field. Taking IrMn/CoFeB/MgO material system for example, the factors affecting the precession of magnetization are investigated, such as the effect of the exchange bias field, the VCMA effect and the mechanism of SOT field-like torque. Considering the practical applications, the effect of the deviation of the fabrication process of magnetic tunnel junctions is also analyzed. The simulation results demonstrate that the combined effect of &lt;inline-formula&gt;&lt;tex-math id="M5"&gt;\begin{document}$ {{\boldsymbol{H}}_{{\text{EB}}}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M5.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M5.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; with VCMA effect can greatly reduce the critical &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;SOT&lt;/sub&gt;, thus assisting and realizing the complete field-free magnetization reversal; the SOT field-like torque plays a dominant role in realizing the magnetization reversal, and by adjusting the ratio of the SOT field-like torque to the damping-like torque, field free switching can be realized in the device at the ps grade ; and the MTJ can realize effective switching when the deviation of oxide thickness &lt;inline-formula&gt;&lt;tex-math id="M6"&gt;\begin{document}$ {\gamma _{{\text{tf}}}} \leqslant 10{\text{%}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M6.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M6.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; or the deviation of free layer thickness &lt;inline-formula&gt;&lt;tex-math id="M7"&gt;\begin{document}$ {\gamma _{{\text{tox}}}} \leqslant 13{\text{%}}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M7.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="19-20230901_M7.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;. Spin-orbit torque devices based on the antiferromagnetic without external magnetic field will provide highly promising solutions for a new-generation ultra-low power, ultra-high speed, and ultra-high integration devices and circuits.