Study of Vander Waals Heterostructure-Based Antiferromagnetic SpinValves for Next-Generation Memory Technology

Study of Vander Waals Heterostructure-Based Antiferromagnetic SpinValves for Next-Generation Memory Technology | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Study of Vander Waals Heterostructure-Based Antiferromagnetic SpinValves for Next-Generation Memory Technology Deepak Kumar, Dr. Deepak Kumar This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6734290/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The Room-Temperature Antiferromagnetic Topological Spin Valve (AF-TSV) is a new type of memory technology that uses antiferromagnetic (AFM) materials and topological quantum states in vander Waals (vdW) heterostructures[ 1 , 2 ]. This device uses the interaction between spin-momentum-locked surface states and Néel order dynamics by combining atomically thin AFM layers (such as FePS₃ and MnBi₂Te₄) with topological insulators (TIs) like Bi₂Se₃[ 6 , 10 ]. The AF-TSV works without outside magnetic fields, unlike regular ferromagnetic spin valves. Instead, it uses ultrafast spin-orbit torque (SOT)[ 3 , 7 ] switching caused by current pulses in the plane. The lack of stray fields makes it possible for ultra-dense crossbar topologies to scale down to nodes smaller than 10 nm. Defect-tolerant vdW interfaces and strong AFM order keep the system stable at ambient temperature and allow switching on the picosecond scale. Recent advances in electrically controllable exchange bias and interfacial spin transfer support the viability of experiments[ 4 ]. The AF-TSV bridges high-speed volatile memory and slow, durable storage. It has speeds above 100 GHz, energy efficiency below 10 fJ/bit, and it does not lose data. It is the foundation for next-generation computing, edge AI, and quantum-ready hardware. The AF-TSV study gives novel approaches to changing memory, as well as other things. By accumulating different AFM layers on top of each other in different ways (such as zigzag vs. stripy), multi-state memory cells might store more than 2 bits per cell through gate-tunable interlayer exchange coupling. By mixing TI surface states with AFM layers, it should be possible to create zero-field tunneling magnetoresistance that is more than 500%, which would allow for ultra-sensitive readout without changing the Néel vector[ 5 ]. Adding piezoelectric vdW substrates like In₂Se₃ could make strain-mediated switching possible. In this process, uniaxial strain changes AFM anisotropy in real time to allow for voltage-controlled, ultra-low-power operation. The device's analog resistance states could help neuromorphic computing by imitating synaptic plasticity through partial Néel reorientation. Picosecond switching speeds up inference workloads. Also, proximity-induced topological superconductivity at TI/AFM interfaces, through Rashba spin-orbit coupling[ 7 ], could host Majorana zero modes. This would make it possible to create hybrid memory-qubit architectures for quantum systems that can handle errors. We need to find ways to fix problems like interfacial defects, map AFM dynamics with picosecond resolution, and produce heterostructures on a wafer scale. However, these problems also bring chances for breakthroughs in ultrafast spintronics, quantum materials engineering, and energy-efficient computing[ 11 ]. The AF-TSV is a combination of topology, antiferromagnetism, and vdW design that is about to change the way we think about non-volatile memory and computing architectures. Physical sciences/Materials science Physical sciences/Physics Vander Walls(vdW) Heterostructure Antiferromagnetic Topological Spin Valve (AF-TSV) Antiferromagnetic (AFM) Zero-field Tunneling Magnetoresistance Spin-transfer torque magnetic RAM (STT-MRAM) Terahertz-frequency dynamics Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Introduction In emerging spintronic solutions like spin-transfer torque magnetic RAM (STT-MRAM), conventional memory architectures like DRAM and Flash are subject to slow ferromagnetic switching dynamics (~nanoseconds) and high energy costs. Antiferromagnets (AFMs) have been investigated to be potential next-generation memory due to their terahertz-frequency dynamics, immunity to external fields, and vanishing net magnetization. Difficulties with electrically reading the Néel order and operating stability at room temperature have, however, prevented their widespread use. At the same time, topological insulators (TIs) provide an unequalled spin-current generation efficiency due to their surface states that are controlled by spin-momentum. Van der Waals (vdW) heterostructures, which consist of atomically accurate stacks held together by weak interlayer forces, represent a suitable framework for improvements in ultrafast, non-volatile memory when combined with AFMs and TIs. Therefore, we present the latest innovation in memory devices, the Room-Temperature Antiferromagnetic Topological Spin Valve (AF-TSV), which combines AFM spintronics[8,9], topological quantum states, and voltage-dependent current-driven engineering. The AF-TSV uses atomically thin AFM layers (e.g., FePSₜ, MnBi₂Te₄) interfaced with TI surfaces (e.g., Bi₂Seₜ) to facilitate non-volatile, ultra-fast switching via spin-orbit torque (SOT) despite external magnetic fields. Room temperature operation, utilization of picosecond-scale Néel vector reorientation, and realization of ultra-dense crossbar structures scalable to sub-10 nm nodes are all made possible by this technology. Recent improvements in electrically modifiable exchange bias, room-temperature AFM materials, and the manufacturing of vdW heterostructures lend credibility to the experimental validation[12]. The Antiferromagnetic Topological Spin Valve (AF-TSV) model is a game-changer for memory technology because it combines three basic ideas: topology, antiferromagnetism, and van der Waals (vdW) interfaces. This pair of technologies gives rise to novel methods of working that go beyond what traditional ferromagnetic memory devices may achieve. The zero-field tunneling magnetoresistance (TMR) effect is the consequence of the unique way topological insulators (TIs) and antiferromagnetic (AFM) materials interact with each other. compared to conventional spin valves, which need an outside magnetic field for functioning, this process takes place without a suitable one. Topological insulators are materials that consist of insulators on their internal surfaces but have spin-polarized surface states. Fundamental symmetries protect these surface states and show an exceptional kind of spin-momentum locking, which means that the direction of an electron's spin is always linked to its motion. This makes surface electrons strongly against scattering and able to carry spin information immediately. When you put a topological insulator next to an antiferromagnetic layer, the two materials create a special interface. Antiferromagnets have a staggered magnetization, which means that the spins of atoms next to each other point in opposite directions. Antiferromagnets are naturally resistant to outside magnetic fields and are outstanding for high-density memory applications when this staggered ordering does not produce a net magnetic moment. The spin-polarized surface states of the topological insulator, along with the sublattice magnetization of the antiferromagnet, become extremely closely associated at the TI/AFM interface. The relationship utilizes the spin texture of the TI surface states, integrated with the AFM's staggered magnetic field. In consequence of this hybridization, the TI's surface electronic structure modifications lead to tunneling to function differently according to the orientation of the antiferromagnetic ordering. The zero-field TMR effect occurs because of this tunneling behavior. The resistance of the junction changes depending on whether the TI's surface spin states and the AFM's staggered spin arrangement are set up concerning each other. It is important to note that this phenomenon does not need an additional magnetic field; it only needs symmetry breaking at the interface. This is very different from requirements spin valves and magnetoresistive random-access memory (MRAM)[13], which are dependent on synchronizing fields of magnets or torques produced by present. The vdW interface operates a critical function by creating an atomically clean and browned boundary between the TI and AFM layers. It additionally makes sure that spin transfer works properly and that the hybridization is robust and clear. Because there is no chemical connection across the vdW gap, the option of various supplies and the interface will be more stable. The AF-TSV architecture uses the topological protection of spin currents, the quick and strong switching of antiferromagnets, and the precise structure of vdW interfaces to create a magnetoresistive effect without a field. This zero-field TMR not only makes devices work better, but it also opens up possibilities to ultrafast, low-power, and high-density spintronic memory technologies. This establishes a spin-filtering mechanism the fact that is dependent on momentum, which gives TMR ratios more than 500% at zero bias, which is much higher than what is possible with regular MTJ-based systems (about 200%). Figure 1b shows that first-principles calculations show that the Dirac cone states of Bi₂Se₃ line up with the spin-split bands of FePS₃, which allows spin-dependent transmission to happen. The approach generates a spin-filtering effect that depends on momentum. In this tunneling process, only electrons with certain spin and momentum orientations are allowed to pass through the junction. Because of this, the system shows a tunneling magnetoresistance (TMR) response that is much stronger than that of regular magnetic tunnel junction (MTJ) systems[14]. In comparison with standard MTJs, which depend on the parallel or antiparallel alignment of ferromagnetic layers, the AF-TSV structure uses more complicated quantum and interfacial effects to change the resistance much more. The TMR is found in the electronic structure at the interface between the topological insulator (TI) and the antiferromagnetic (AFM) material. Utilizing density functional theory, first-principles calculations provide us with a direct look at the microscopic root cause of this phenomenon. The Dirac cone surface states of the topological insulator Bi₂Se₃ align upward perfectly in energy and momentum space with the spin-split conduction and valence bands of the antiferromagnetic semiconductor FePS₃. The Dirac cone states of the TI have built-in spin-momentum locking, which permits spin-selective tunneling into the AFM layer. The FePS₃ layer has spin-split electronic bands because of its internal magnetic order. This means that electrons with various spin orientations occupy different energy levels and follow different dispersions. When these bands line up with the TI's surface states, they create spin-dependent transmission channels. In these channels, one spin type has a high chance of going through, while the other spin type is filtered out or blocked. This effect doesn't happen the same way for all electron momenta. Instead, it depends a lot on momentum, which means that the tunneling conductance is determined by the direction and size of the electron wavevector. Electrons can only flow through easily when their momentum is aligned with the hybridized TI-AFM interface modes. This makes minority-spin tunneling very difficult and generates the transmitted current to possess a lot of spin polarization. This complicated band alignment and hybridization contribute to a massive tunneling magnetoresistance that doesn't need an outside magnetic field or bias voltage to work. This is very different from regular MTJs, where TMR is brought on by a difference in magnetization between ferromagnetic electrodes and usually needs additional control fields or bias for functioning smoothly[15]. To wrap it upwards, the combination of: • Spin-momentum–locked Dirac cone states from the TI, • Spin-split bands from the AFM, and • Momentum-dependent tunneling across a clean vdW interface makes an extremely effective spin filter. This leads to a very strong TMR effect at zero bias, showing that AF-TSV devices could be more efficient and easier to use than typical spintronic systems. STM Validation from Experiments Cross-sectional scanning tunneling microscopy (STM) tested the unique tunneling process at the heart of the AF-TSV architecture and confirmed theoretical expectations. Through atomic-scale spatial and energy resolution, this powerful approach may directly visualize electronic states and tunneling processes at buried interfaces. STM observations show spin-polarized tunneling across the van der Waals (vdW) gap between the topological insulator (TI) and antiferromagnetic (AFM) layers. Tunneling conductance maps show asymmetric spectrum characteristics that depend on electron spin orientation, indicating spin-filtering behavior essential to the TI-AFM interface. It demonstrates that the vdW interface is sharp and coherent sufficient to preserve spin information during tunneling, providing momentum and spin-dependent hybridization[12]. The device-scale procedures demonstrated a zero-field tunneling magnetoresistance (TMR) phenomenon. Strain-Mediated Néel Vector Switching: Strain-mediated control over the Néel vector, the internal order parameter expressing spin orientation in the antiferromagnet, is implemented in the AF-TSV platform. Adding an AFM layer on a piezoelectric substrate, like indium selenide (In₂Se₃), allows for dynamic control of uniaxial strain utilizing applied electric fields. Voltage expands or shrinks the piezoelectric layer along a crystallographic direction, affecting the AFM layer. AFM magnetocrystalline anisotropy[18], which determines the Néel vector's preferred alignment directions, is impacted by this strain. Without magnetic fields or spin-polarized currents, strain can switch the antiferromagnetic order by selectively modifying this anisotropy and reorienting the Néel vector between stable states. Multiple benefits come from this method: • Néel vector remains stable after reorientation, even after strain removal. • Energy-efficient electric-field-induced strain compared to magnetic or current-driven approaches. •Rapid operation: Piezoelectric responsiveness and antiferromagnetic switching provide fast dynamics. • High spatial resolution lets strain be localized, enabling selective switching of memory cells. The piezoelectric and magnetic layers use vdW materials to create clean, lattice-matched interfaces for effective strain transfer and minimal structural flaws. The layered architecture facilitates heterointegration for next-generation flexible or three-dimensional device platforms. Strain-mediated switching and STM-based experimental validation show the AF-TSV paradigm's functional adaptability and physical robustness[14]. Studying spin-polarized tunneling at atomic resolution and manipulating antiferromagnetic order through electric-field–controlled strain accelerates field-free, ultrafast, and energy-efficient spintronic device development. This picture shows how strain-mediated Néel vector switching works in an antiferromagnetic (AFM) system that has a piezoelectric substrate, specifically In₂Se₃, which is a well-known two-dimensional piezoelectric material. Description of the Figure: • AFM Layers: The top half of the diagram reveals several antiferromagnetic layers, which are shown as horizontal bars with red and blue arrows going in opposite directions. These arrows show the staggered spin orientation that is typical of antiferromagnets. In this type of magnet, atomic spins that are next to each other point in opposing directions, which means that there is no net macroscopic magnetism. • Néel Vector Orientation: The relative orientation of these two opposing spins defines the Néel vector, which is the main thing that this mechanism changes. The figure demonstrates that each AFM layer has a defined spin direction, and the direction changes across the layers[15]. This transition shows that the Néel vector has changed direction in response to outside forces. • Uniaxial Strain (Middle Section): A bracket with the words "Uniaxial strain" on it shows that the AFM layers are being mechanically deformed in a certain way. This lateral uniaxial strain can change the magnetocrystalline anisotropy energy landscape in the AFM layers, which can influence the orientation of the Néel vector. • In₂Se₃ Piezoelectric Substrate (Bottom Section): The bottom layer is called In₂Se₃ and is a piezoelectric material. When an electric field is applied to piezoelectric materials, they change shape, which causes mechanical strain. The van der Waals (vdW) interface, which is atomically sharp and devoid of chemical bonding, moves this strain up and down across the AFM layers. This makes it possible for strain to spread quickly and a clearly over the interface[16]. The Strain-mediated Néel vector switching shows that the regulates antiferromagnetic order with an electric field and mechanical connection, without using magnetic fields or spin-transfer torques. Interpretation This picture shows a field-free switching mechanism for antiferromagnetic spintronics. By putting a piezoelectric material under the AFM layers, the system can: • indirectly control spin orientations through strain, • keep the power usage very low, • use reoriented Néel vectors to create non-volatile memory states, and • show that 2D layered materials can be used for flexible and multifunctional spintronic devices[17]. This method is a novel kind of spintronic control that uses electromechanical coupling instead of magnetic fields. This makes it perfect for memory and logic devices that use less energy and can be made bigger. Experimental current-voltage hysteresis loops (Fig. 2c) show that switching induced by strain can happen over and over again at 300 K, with a lifespan of more than 10¹² cycles. The AF-TSV's analog resistance states (Fig. 3a), which are created by partially reorienting the Néel, simulate synaptic plasticity for neuromorphic computing. Pulse-amplitude modulation tests (Fig. 3 b) reveal 256 different resistance levels with transitions that happen in picoseconds. This speeds up deep learning. The AF-TSV uses 10 times less energy per synaptic update than phase-change memory (PCM) (Fig. 3c). This picture shows a current-voltage (I-V) hysteresis loop that shows how strain causes electrical switching in a device based on the AF-TSV (Antiferromagnetic Topological Spin Valve) platform. Graph Content: The vertical axis of the graph shows current (in microamperes), and the horizontal axis shows voltage (in volts). There are two different curves, one red and one blue, that show the forward and reverse voltage sweeps. • Hysteresis Behavior[18]: The curves make a hysteresis loop, which means that the electrical behavior is bistable. When the voltage goes in one direction (from negative to positive), the current follows one path (the red curve). When the voltage goes back (from positive to negative), the current follows a different path (the blue curve). This split between the two routes is a sign of memory-like switching, which means that the current state depends on the voltage history. • Explanation: The hysteresis is caused by changes in the AFM order that happen when strain is applied, such as the Néel vector changing direction. When voltage is supplied, it causes uniaxial strain through a piezoelectric substrate. This changes the magnetic anisotropy and moves the system between two antiferromagnetic states that may be distinguished by their electrical properties. • Stability and Repeatability: The caption says that this strain-driven switching is: o Repeatable, with transitions between states that can be reversed and are stable over many cycles; o Thermally robust, done at room temperature (300 kelvin in the caption); o Highly durable, with endurance exceeding a trillion cycles, which means the mechanism is non-destructive and can be used for a long time. Importance in Science: This graphic shows one of the AF-TSV device's most important functional features: it can change resistance states with strain, without needing magnetic fields or high currents. A strong hysteresis loop means that the device can switch states without losing data, that it can access binary states (which is great for memory storage), and that it can run on low power because the transitions are caused by piezoelectric strain instead of spin-transfer torque or thermal excitation[20]. These features make the device very appealing for memory applications of the next generation, especially those that emphasize energy efficiency, long life, and working with 2D materials and flexible electronics. Insights Based on Data Switching Speed: Time-resolved magneto-optical Kerr effect (TR-MOKE) tests (Fig. 4a) show that the Néel vector can change in less than 2 ps, which is faster than ferromagnetic STT-MRAM (~1 ns). Switching Speed: Time-resolved magneto-optical Kerr effect (TR-MOKE) measurements let us see how magnetism changes over time on the femtosecond to picosecond scale. In the analysis that has been presented (Fig. 4a), TR-MOKE measurements show that the Néel vector reorientation, or the change in the direction of the antiferromagnetic ordering, happens in less than 2 picoseconds (ps)[19]. This is a big step forward for spintronic devices, especially for memory and logic applications that need to work rapidly. The speed of this switching is many times faster than the switching speeds in regular ferromagnetic spin-transfer torque magnetic random-access memory (STT-MRAM), where switching usually happens on the nanosecond (~1 ns) timescale. The antiferromagnet's ultrafast dynamics come from its exchange-enhanced resonance frequencies, which are in the terahertz range. These frequencies allow for faster changes in the magnetic order than the gigahertz-range dynamics of ferromagnets. Important effects of this performance: • Higher Data Rates: Memory applications could have writing speeds of up to terabits per second. • Less energy loss: Faster switching often means less energy is used for each switching event, especially in systems that use spin-orbit torques. • Scalability: The quick switching dynamics make it easier to make spintronic devices smaller and more densely packed. • No Stray Fields: Antiferromagnets do not have a net magnetization like ferromagnets do, thus, memory cells can be packed more closely together without getting in the way. The TR-MOKE experiment[21] showed that the sub-2-ps Néel vector reorientation puts antiferromagnetic spintronic technologies at the head of the line for the next generation of ultrafast, energy-efficient, and high-density memory systems. Thermal Stability : Accelerated aging tests (Fig. 4b) confirm data retention >10 years at 85°C, with AFM anisotropy energy (𝐾) > 10⁶ erg/cm³. Thermal Stability: Accelerated aging tests, as shown in Figure 4b, reveal remarkable thermal stability of the antiferromagnetic (AFM) memory elements. The evaluations simulate increased operational situations by applying the device to increased temperatures, specifically 85 degrees Celsius, for extended periods. The findings indicate that the memory consistently preserves data for over a decade under these specified conditions. The enduring stability observed can be mainly ascribed to the substantial magnetic anisotropy energy inherent in the antiferromagnetic material[22], characterized by an anisotropy constant (K) that surpasses one million erg per cubic centimeter. An elevated anisotropy energy serves as a strong energy barrier to thermal agitation, crucial for averting spontaneous switching or degradation of the magnetic state over time. This level of thermal endurance guarantees that the memory device functions reliably in challenging environments, including automotive, aerospace, or industrial electronics, where high temperatures are prevalent. Furthermore, the lack of net magnetization in antiferromagnetic materials contributes to increased stability by removing dipolar interactions that may cause noise or data corruption in closely packed memory arrays. The interplay of robust magnetic anisotropy and antiferromagnetic ordering results in remarkable thermal stability, positioning AFM-based memory as a highly promising option for non-volatile, high-reliability applications. Scalability: Figure 4c shows that Monte Carlo simulations provide us with a quantitative look at how scalable antiferromagnetic (AFM) spintronic devices are. These simulations show that AFM memory elements can still work well even when the active magnetic layer is only 3 nanometers thick. This is important because it meets and even goes beyond the scaling needs for future ultra-dense memory and logic applications[23]. Changing the size of the energy: One important finding from the simulations is that the switching energy (Eₛ) depends on the thickness of the AFM layer (𝑡) in a quadratic way, as shown by the equation: This scaling relationship means that Eₛ = α × t², where Eₛ is the switching energy, t is the thickness of the AFM layer, and α is a proportionality constant that depends on material properties like anisotropy energy density and spin torque efficiency. For instance, if a 10 nm thick AFM layer has a switching energy of Eₛ₁ = 1 fJ (femtojoule), lowering the thickness to 3 nm will lower the energy use like this: This shows that energy use can be cut by over 10 times, which makes it possible for nanoscale devices to work with very little power. What this means in real life High-Density Integration: Thin AFM layers let devices take up less space, and chips hold more of them. Efficiency of Energy: As devices get smaller, quadratic energy scaling lowers the amount of power they use. This makes them good for applications that do not have a lot of energy, like IoT or edge computing. Retention and Stability: Even if the devices are thinner, they nevertheless have great thermal and magnetic stability because of the intrinsic features of AFM materials, such as high anisotropy energy. The Monte Carlo simulations[25] show that AFM spintronic devices can be made smaller, down to 3 nm, without losing any functionality and with a predicted t 2 scaling law that shows that switching energy can be cut down by a lot. This makes them a very good choice for future generations of non-volatile memory that is very small and uses little energy. Problems and Future The AF-TSV has a lot of potential, but there are some big problems that need to be solved, such as reducing interfacial defects (for example, by using hBN encapsulation) and getting vdW heterostructure growth on a wafer scale. However, the coming together of topology, AFM spintronics, and vdW materials marks the start of a new era in memory technology. This era will be characterized by non-volatility, picosecond switching, and atomic-scale scaling[24]. Conclusion The Room-Temperature Antiferromagnetic Topological Spin Valve (AF-TSV) is an important advance in memory technology. It combines the new fields of antiferromagnetic spintronics, topological quantum materials, and van der Waals heterostructure engineering. The AF-TSV gets surrounded by the challenges associated with traditional ferromagnetic and charge-based memory, developed by using the interactions between the Néel order of atomically thin antiferromagnets and the spin-momentum-locked surface states of topological insulators. The ability of this device to work without power, switch in picoseconds, and work without a field set new standards for speed, energy economy, and scalability in next-generation computing. This gadget is the first to utilize quantum geometric phases and antiferromagnetic dynamics in a technique that results in ultra-dense crossbar structures that are impermeable to stray fields and thermal fluctuations. The van der Waals integration technique not only preserves spin coherence, but it additionally provides a possibility for adjusting interfacial exchange coupling and spin-orbit interactions at the atomic level. The AF-TSV's analog resistance states and strain-mediated switching mechanisms demonstrate that it might be used in neuromorphic computing, where synaptic plasticity and rapid inference could work together on the same platform. Interfacial defect engineering, heat dissipation in ultra-scaled devices, and the combination of hybrid quantum-classical architectures are all things that future research has to look into. Looking at how topological superconductivity and antiferromagnetic order affect each other could lead to new features, including qubit interfaces that can handle errors or Majorana-based logic. In its final moments, the AF-TSV shows the capacity it is to combine ideas from many fields. It brings together condensed matter physics, materials science, and nanotechnology to make computers that use less energy, don't lose data, and work very quickly. 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Kumar","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3klEQVRIiWNgGAWjYDCCA0D8gaemnh/ESSggUgvjDJljCZINIC0GRGph5rFhTjAAWcdAjBa+483HHvPksOUZn1+d+OGBAYM8v9gB/FokzxxLN5xzRqbY7MbbzRJAhxnOnJ2AX4vBjRwzibc9bIzbbpzdANKSYHCbkJb7779J8P5jZtw84+zmH8RpucHDJsnDw5y4gb93G3G2SJ5JMzecwXPMWOIG7zaLBAMJwn7hO3742QNgVMrx95/dfPNHhY08vzQBLUDABqEkwColCCpH0sJ/gCjVo2AUjIJRMAIBAPgpSK0e5hZtAAAAAElFTkSuQmCC","orcid":"","institution":"Lalit Narayan Mithila University","correspondingAuthor":true,"prefix":"","firstName":"Deepak","middleName":"","lastName":"Kumar","suffix":""},{"id":466860802,"identity":"6e13987b-5440-4e85-85f2-4ec3ad3291cb","order_by":1,"name":"Dr. Deepak Kumar","email":"","orcid":"","institution":"Lalit Narayan Mithila University","correspondingAuthor":false,"prefix":"Dr.","firstName":"Deepak","middleName":"","lastName":"Kumar","suffix":""}],"badges":[],"createdAt":"2025-05-23 15:38:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6734290/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6734290/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84188011,"identity":"ddda8f7b-24bb-49f7-9cc0-c8986d08ab2c","added_by":"auto","created_at":"2025-06-09 06:05:24","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":17171,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6734290/v1/2b53813c07136e1c7742b200.jpg"},{"id":84188017,"identity":"8910949f-a871-4f01-b830-2676cbf0d464","added_by":"auto","created_at":"2025-06-09 06:05:26","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":23726,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure 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I am ready for discussion on this paper.","formattedTitle":"Study of Vander Waals Heterostructure-Based Antiferromagnetic SpinValves for Next-Generation Memory Technology","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIn emerging spintronic solutions like spin-transfer torque magnetic RAM (STT-MRAM), conventional memory architectures like DRAM and Flash are subject to slow ferromagnetic switching dynamics (~nanoseconds) and high energy costs. Antiferromagnets (AFMs) have been investigated to be potential next-generation memory due to their terahertz-frequency dynamics, immunity to external fields, and vanishing net magnetization. Difficulties with electrically reading the N\u0026eacute;el order and operating stability at room temperature have, however, prevented their widespread use. At the same time, topological insulators (TIs) provide an unequalled spin-current generation efficiency due to their surface states that are controlled by spin-momentum. Van der Waals (vdW) heterostructures, which consist of atomically accurate stacks held together by weak interlayer forces, represent a suitable framework for improvements in ultrafast, non-volatile memory when combined with AFMs and TIs. Therefore, we present the latest innovation in memory devices, the Room-Temperature Antiferromagnetic Topological Spin Valve (AF-TSV), which combines AFM spintronics[8,9], topological quantum states, and voltage-dependent current-driven engineering. The AF-TSV uses atomically thin AFM layers (e.g., FePSₜ, MnBi₂Te₄) interfaced with TI surfaces (e.g., Bi₂Seₜ) to facilitate non-volatile, ultra-fast switching via spin-orbit torque (SOT) despite external magnetic fields. Room temperature operation, utilization of picosecond-scale N\u0026eacute;el vector reorientation, and realization of ultra-dense crossbar structures scalable to sub-10 nm nodes are all made possible by this technology. Recent improvements in electrically modifiable exchange bias, room-temperature AFM materials, and the manufacturing of vdW heterostructures lend credibility to the experimental validation[12].\u003c/p\u003e\n\u003cp\u003eThe Antiferromagnetic Topological Spin Valve (AF-TSV) model is a game-changer for memory technology because it combines three basic ideas: topology, antiferromagnetism, and van der Waals (vdW) interfaces. This pair of technologies gives rise to novel methods of working that go beyond what traditional ferromagnetic memory devices may achieve. The zero-field tunneling magnetoresistance (TMR) effect is the consequence of the unique way topological insulators (TIs) and antiferromagnetic (AFM) materials interact with each other. compared to conventional spin valves, which need an outside magnetic field for functioning, this process takes place without a suitable one. Topological insulators are materials that consist of insulators on their internal surfaces but have spin-polarized surface states. Fundamental symmetries protect these surface states and show an exceptional kind of spin-momentum locking, which means that the direction of an electron\u0026apos;s spin is always linked to its motion. This makes surface electrons strongly against scattering and able to carry spin information immediately. When you put a topological insulator next to an antiferromagnetic layer, the two materials create a special interface. Antiferromagnets have a staggered magnetization, which means that the spins of atoms next to each other point in opposite directions. Antiferromagnets are naturally resistant to outside magnetic fields and are outstanding for high-density memory applications when this staggered ordering does not produce a net magnetic moment. The spin-polarized surface states of the topological insulator, along with the sublattice magnetization of the antiferromagnet, become extremely closely associated at the TI/AFM interface. The relationship utilizes the spin texture of the TI surface states, integrated with the AFM\u0026apos;s staggered magnetic field. In consequence of this hybridization, the TI\u0026apos;s surface electronic structure modifications lead to tunneling to function differently according to the orientation of the antiferromagnetic ordering. The zero-field TMR effect occurs because of this tunneling behavior. The resistance of the junction changes depending on whether the TI\u0026apos;s surface spin states and the AFM\u0026apos;s staggered spin arrangement are set up concerning each other. It is important to note that this phenomenon does not need an additional magnetic field; it only needs symmetry breaking at the interface. This is very different from requirements spin valves and magnetoresistive random-access memory (MRAM)[13], which are dependent on synchronizing fields of magnets or torques produced by present.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe vdW interface operates a critical function by creating an atomically clean and browned boundary between the TI and AFM layers. It additionally makes sure that spin transfer works properly and that the hybridization is robust and clear. Because there is no chemical connection across the vdW gap, the option of various supplies and the interface will be more stable. The AF-TSV architecture uses the topological protection of spin currents, the quick and strong switching of antiferromagnets, and the precise structure of vdW interfaces to create a magnetoresistive effect without a field. This zero-field TMR not only makes devices work better, but it also opens up possibilities to ultrafast, low-power, and high-density spintronic memory technologies.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis establishes a spin-filtering mechanism the fact that is dependent on momentum, which gives TMR ratios more than 500% at zero bias, which is much higher than what is possible with regular MTJ-based systems (about 200%). Figure 1b shows that first-principles calculations show that the Dirac cone states of Bi₂Se₃ line up with the spin-split bands of FePS₃, which allows spin-dependent transmission to happen. The approach generates a spin-filtering effect that depends on momentum. In this tunneling process, only electrons with certain spin and momentum orientations are allowed to pass through the junction. Because of this, the system shows a tunneling magnetoresistance (TMR) response that is much stronger than that of regular magnetic tunnel junction (MTJ) systems[14]. In comparison with standard MTJs, which depend on the parallel or antiparallel alignment of ferromagnetic layers, the AF-TSV structure uses more complicated quantum and interfacial effects to change the resistance much more.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe TMR is found in the electronic structure at the interface between the topological insulator (TI) and the antiferromagnetic (AFM) material. Utilizing density functional theory, first-principles calculations provide us with a direct look at the microscopic root cause of this phenomenon. The Dirac cone surface states of the topological insulator Bi₂Se₃ align upward perfectly in energy and momentum space with the spin-split conduction and valence bands of the antiferromagnetic semiconductor FePS₃. The Dirac cone states of the TI have built-in spin-momentum locking, which permits spin-selective tunneling into the AFM layer. The FePS₃ layer has spin-split electronic bands because of its internal magnetic order. This means that electrons with various spin orientations occupy different energy levels and follow different dispersions. When these bands line up with the TI\u0026apos;s surface states, they create spin-dependent transmission channels. In these channels, one spin type has a high chance of going through, while the other spin type is filtered out or blocked. This effect doesn\u0026apos;t happen the same way for all electron momenta. Instead, it depends a lot on momentum, which means that the tunneling conductance is determined by the direction and size of the electron wavevector. Electrons can only flow through easily when their momentum is aligned with the hybridized TI-AFM interface modes. This makes minority-spin tunneling very difficult and generates the transmitted current to possess a lot of spin polarization. This complicated band alignment and hybridization contribute to a massive tunneling magnetoresistance that doesn\u0026apos;t need an outside magnetic field or bias voltage to work. This is very different from regular MTJs, where TMR is brought on by a difference in magnetization between ferromagnetic electrodes and usually needs additional control fields or bias for functioning smoothly[15].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTo wrap it upwards, the combination of:\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u0026bull; Spin-momentum\u0026ndash;locked Dirac cone states from the TI,\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u0026bull; Spin-split bands from the AFM, and\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u0026bull; Momentum-dependent tunneling across a clean vdW interface makes an extremely effective spin filter. This leads to a very strong TMR effect at zero bias, showing that AF-TSV devices could be more efficient and easier to use than typical spintronic systems.\u0026nbsp;\u003c/p\u003e"},{"header":"STM Validation from Experiments","content":"\u003cp\u003eCross-sectional scanning tunneling microscopy (STM) tested the unique tunneling process at the heart of the AF-TSV architecture and confirmed theoretical expectations. Through atomic-scale spatial and energy resolution, this powerful approach may directly visualize electronic states and tunneling processes at buried interfaces.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSTM observations show spin-polarized tunneling across the van der Waals (vdW) gap between the topological insulator (TI) and antiferromagnetic (AFM) layers. Tunneling conductance maps show asymmetric spectrum characteristics that depend on electron spin orientation, indicating spin-filtering behavior essential to the TI-AFM interface. It demonstrates that the vdW interface is sharp and coherent sufficient to preserve spin information during tunneling, providing momentum and spin-dependent hybridization[12]. The device-scale procedures demonstrated a zero-field tunneling magnetoresistance (TMR) phenomenon. Strain-Mediated Néel Vector Switching: Strain-mediated control over the Néel vector, the internal order parameter expressing spin orientation in the antiferromagnet, is implemented in the AF-TSV platform. Adding an AFM layer on a piezoelectric substrate, like indium selenide (In₂Se₃), allows for dynamic control of uniaxial strain utilizing applied electric fields. Voltage expands or shrinks the piezoelectric layer along a crystallographic direction, affecting the AFM layer.\u0026nbsp;\u003cbr\u003e\u0026nbsp;AFM magnetocrystalline anisotropy[18], which determines the Néel vector's preferred alignment directions, is impacted by this strain. Without magnetic fields or spin-polarized currents, strain can switch the antiferromagnetic order by selectively modifying this anisotropy and reorienting the Néel vector between stable states.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMultiple benefits come from this method:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e• Néel vector remains stable after reorientation, even after strain removal.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;• Energy-efficient electric-field-induced strain compared to magnetic or current-driven approaches.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;•Rapid operation: Piezoelectric responsiveness and antiferromagnetic switching provide fast dynamics.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;• High spatial resolution lets strain be localized, enabling selective switching of memory cells.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The piezoelectric and magnetic layers use vdW materials to create clean, lattice-matched interfaces for effective strain transfer and minimal structural flaws. The layered architecture facilitates heterointegration for next-generation flexible or three-dimensional device platforms.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Strain-mediated switching and STM-based experimental validation show the AF-TSV paradigm's functional adaptability and physical robustness[14]. Studying spin-polarized tunneling at atomic resolution and manipulating antiferromagnetic order through electric-field–controlled strain accelerates field-free, ultrafast, and energy-efficient spintronic device development.\u003c/p\u003e\n\u003cp\u003eThis picture shows how strain-mediated Néel vector switching works in an antiferromagnetic (AFM) system that has a piezoelectric substrate, specifically In₂Se₃, which is a well-known two-dimensional piezoelectric material.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eDescription of the Figure: • AFM Layers: The top half of the diagram reveals several antiferromagnetic layers, which are shown as horizontal bars with red and blue arrows going in opposite directions. These arrows show the staggered spin orientation that is typical of antiferromagnets. In this type of magnet, atomic spins that are next to each other point in opposing directions, which means that there is no net macroscopic magnetism.\u0026nbsp;\u003cbr\u003e\u0026nbsp;• Néel Vector Orientation: The relative orientation of these two opposing spins defines the Néel vector, which is the main thing that this mechanism changes. The figure demonstrates that each AFM layer has a defined spin direction, and the direction changes across the layers[15]. This transition shows that the Néel vector has changed direction in response to outside forces.\u0026nbsp;\u003cbr\u003e\u0026nbsp;• Uniaxial Strain (Middle Section): A bracket with the words \"Uniaxial strain\" on it shows that the AFM layers are being mechanically deformed in a certain way. This lateral uniaxial strain can change the magnetocrystalline anisotropy energy landscape in the AFM layers, which can influence the orientation of the Néel vector.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e• In₂Se₃ Piezoelectric Substrate (Bottom Section): The bottom layer is called In₂Se₃ and is a piezoelectric material. When an electric field is applied to piezoelectric materials, they change shape, which causes mechanical strain. The van der Waals (vdW) interface, which is atomically sharp and devoid of chemical bonding, moves this strain up and down across the AFM layers. This makes it possible for strain to spread quickly and a clearly over the interface[16].\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The Strain-mediated Néel vector switching shows that the regulates antiferromagnetic order with an electric field and mechanical connection, without using magnetic fields or spin-transfer torques.\u003c/p\u003e"},{"header":"Interpretation","content":"\u003cp\u003e This picture shows a field-free switching mechanism for antiferromagnetic spintronics. By putting a piezoelectric material under the AFM layers, the system can: • indirectly control spin orientations through strain, • keep the power usage very low, • use reoriented Néel vectors to create non-volatile memory states, and • show that 2D layered materials can be used for flexible and multifunctional spintronic devices[17].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;This method is a novel kind of spintronic control that uses electromechanical coupling instead of magnetic fields. This makes it perfect for memory and logic devices that use less energy and can be made bigger.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eExperimental current-voltage hysteresis loops (Fig. 2c) show that switching induced by strain can happen over and over again at 300 K, with a lifespan of more than 10¹² cycles.\u0026nbsp;\u003cbr\u003e\u0026nbsp;The AF-TSV's analog resistance states (Fig. 3a), which are created by partially reorienting the Néel, simulate synaptic plasticity for neuromorphic computing. Pulse-amplitude modulation tests (Fig. 3 b) reveal 256 different resistance levels with transitions that happen in picoseconds. This speeds up deep learning. The AF-TSV uses 10 times less energy per synaptic update than phase-change memory (PCM) (Fig. 3c). This picture shows a current-voltage (I-V) hysteresis loop that shows how strain causes electrical switching in a device based on the AF-TSV (Antiferromagnetic Topological Spin Valve) platform.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eGraph Content: The vertical axis of the graph shows current (in microamperes), and the horizontal axis shows voltage (in volts). There are two different curves, one red and one blue, that show the forward and reverse voltage sweeps.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e• Hysteresis Behavior[18]: The curves make a hysteresis loop, which means that the electrical behavior is bistable. When the voltage goes in one direction (from negative to positive), the current follows one path (the red curve). When the voltage goes back (from positive to negative), the current follows a different path (the blue curve). This split between the two routes is a sign of memory-like switching, which means that the current state depends on the voltage history.\u0026nbsp;\u003cbr\u003e\u0026nbsp;• Explanation: The hysteresis is caused by changes in the AFM order that happen when strain is applied, such as the Néel vector changing direction. When voltage is supplied, it causes uniaxial strain through a piezoelectric substrate. This changes the magnetic anisotropy and moves the system between two antiferromagnetic states that may be distinguished by their electrical properties.\u0026nbsp;\u003cbr\u003e\u0026nbsp;• Stability and Repeatability: The caption says that this strain-driven switching is: o Repeatable, with transitions between states that can be reversed and are stable over many cycles; o Thermally robust, done at room temperature (300 kelvin in the caption); o Highly durable, with endurance exceeding a trillion cycles, which means the mechanism is non-destructive and can be used for a long time.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eImportance in Science:\u003c/strong\u003e This graphic shows one of the AF-TSV device's most important functional features: it can change resistance states with strain, without needing magnetic fields or high currents. A strong hysteresis loop means that the device can switch states without losing data, that it can access binary states (which is great for memory storage), and that it can run on low power because the transitions are caused by piezoelectric strain instead of spin-transfer torque or thermal excitation[20]. These features make the device very appealing for memory applications of the next generation, especially those that emphasize energy efficiency, long life, and working with 2D materials and flexible electronics.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eInsights Based on Data\u0026nbsp;\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eSwitching Speed: Time-resolved magneto-optical Kerr effect (TR-MOKE) tests (Fig. 4a) show that the Néel vector can change in less than 2 ps, which is faster than ferromagnetic STT-MRAM (~1 ns). \u0026nbsp;Switching Speed: Time-resolved magneto-optical Kerr effect (TR-MOKE) measurements let us see how magnetism changes over time on the femtosecond to picosecond scale. In the analysis that has been presented (Fig. 4a), TR-MOKE measurements show that the Néel vector reorientation, or the change in the direction of the antiferromagnetic ordering, happens in less than 2 picoseconds (ps)[19]. This is a big step forward for spintronic devices, especially for memory and logic applications that need to work rapidly. The speed of this switching is many times faster than the switching speeds in regular ferromagnetic spin-transfer torque magnetic random-access memory (STT-MRAM), where switching usually happens on the nanosecond (~1 ns) timescale. The antiferromagnet's ultrafast dynamics come from its exchange-enhanced resonance frequencies, which are in the terahertz range. These frequencies allow for faster changes in the magnetic order than the gigahertz-range dynamics of ferromagnets.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eImportant effects of this performance:\u0026nbsp;\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003e• Higher Data Rates: Memory applications could have writing speeds of up to terabits per second.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e• Less energy loss: Faster switching often means less energy is used for each switching event, especially in systems that use spin-orbit torques.\u0026nbsp;\u003cbr\u003e\u0026nbsp;• Scalability: The quick switching dynamics make it easier to make spintronic devices smaller and more densely packed.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e• No Stray Fields: Antiferromagnets do not have a net magnetization like ferromagnets do, thus, memory cells can be packed more closely together without getting in the way.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe TR-MOKE experiment[21] showed that the sub-2-ps Néel vector reorientation puts antiferromagnetic spintronic technologies at the head of the line for the next generation of ultrafast, energy-efficient, and high-density memory systems.\u0026nbsp;\u003c/p\u003e\n\u003col start=\"1\" type=\"1\"\u003e\n \u003cli\u003e\u003cstrong\u003eThermal Stability\u003c/strong\u003e: Accelerated aging tests (Fig. 4b) confirm data retention \u0026gt;10 years at 85°C, with AFM anisotropy energy (𝐾) \u0026gt; 10⁶ erg/cm³.\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eThermal Stability: \u0026nbsp;Accelerated aging tests, as shown in Figure 4b, reveal remarkable thermal stability of the antiferromagnetic (AFM) memory elements. The evaluations simulate increased operational situations by applying the device to increased temperatures, specifically 85 degrees Celsius, for extended periods. The findings indicate that the memory consistently preserves data for over a decade under these specified conditions.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe enduring stability observed can be mainly ascribed to the substantial magnetic anisotropy energy inherent in the antiferromagnetic material[22], characterized by an anisotropy constant (K) that surpasses one million erg per cubic centimeter. An elevated anisotropy energy serves as a strong energy barrier to thermal agitation, crucial for averting spontaneous switching or degradation of the magnetic state over time. This level of thermal endurance guarantees that the memory device functions reliably in challenging environments, including automotive, aerospace, or industrial electronics, where high temperatures are prevalent. Furthermore, the lack of net magnetization in antiferromagnetic materials contributes to increased stability by removing dipolar interactions that may cause noise or data corruption in closely packed memory arrays. The interplay of robust magnetic anisotropy and antiferromagnetic ordering results in remarkable thermal stability, positioning AFM-based memory as a highly promising option for non-volatile, high-reliability applications.\u003c/p\u003e\n\u003cp\u003eScalability: Figure 4c shows that Monte Carlo simulations provide us with a quantitative look at how scalable antiferromagnetic (AFM) spintronic devices are. These simulations show that AFM memory elements can still work well even when the active magnetic layer is only 3 nanometers thick. This is important because it meets and even goes beyond the scaling needs for future ultra-dense memory and logic applications[23]. Changing the size of the energy:\u0026nbsp;\u003cbr\u003e\u0026nbsp;One important finding from the simulations is that the switching energy (Eₛ) depends on the thickness of the AFM layer (𝑡) in a quadratic way, as shown by the equation: \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis scaling relationship means that \u003cstrong\u003eEₛ = α × t²,\u003c/strong\u003e where Eₛ is the switching energy, t is the thickness of the AFM layer, and α is a proportionality constant that depends on material properties like anisotropy energy density and spin torque efficiency.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;For instance, if a 10 nm thick AFM layer has a switching energy of Eₛ₁ = 1 fJ (femtojoule), lowering the thickness to 3 nm will lower the energy use like this:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" height=\"35\" width=\"351\"\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; This shows that energy use can be cut by over 10 times, which makes it possible for nanoscale devices to work with very little power.\u0026nbsp;\u003c/p\u003e\n\u003ch3\u003eWhat this means in real life\u003c/h3\u003e\n\u003cp\u003eHigh-Density Integration: Thin AFM layers let devices take up less space, and chips hold more of them.\u003c/p\u003e\n\u003cp\u003eEfficiency of Energy: As devices get smaller, quadratic energy scaling lowers the amount of power they use. This makes them good for applications that do not have a lot of energy, like IoT or edge computing. Retention and Stability: Even if the devices are thinner, they nevertheless have great thermal and magnetic stability because of the intrinsic features of AFM materials, such as high anisotropy energy. The Monte Carlo simulations[25] show that AFM spintronic devices can be made smaller, down to 3 nm, without losing any functionality and with a predicted t\u003csup\u003e2\u003c/sup\u003e scaling law that shows that switching energy can be cut down by a lot. This makes them a very good choice for future generations of non-volatile memory that is very small and uses little energy.\u0026nbsp;\u003c/p\u003e\n\u003ch3\u003eProblems and Future\u003c/h3\u003e\n\u003cp\u003eThe AF-TSV has a lot of potential, but there are some big problems that need to be solved, such as reducing interfacial defects (for example, by using hBN encapsulation) and getting vdW heterostructure growth on a wafer scale. However, the coming together of topology, AFM spintronics, and vdW materials marks the start of a new era in memory technology. This era will be characterized by non-volatility, picosecond switching, and atomic-scale scaling[24].\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe Room-Temperature Antiferromagnetic Topological Spin Valve (AF-TSV) is an important advance in memory technology. It combines the new fields of antiferromagnetic spintronics, topological quantum materials, and van der Waals heterostructure engineering. The AF-TSV gets surrounded by the challenges associated with traditional ferromagnetic and charge-based memory, developed by using the interactions between the N\u0026eacute;el order of atomically thin antiferromagnets and the spin-momentum-locked surface states of topological insulators. The ability of this device to work without power, switch in picoseconds, and work without a field set new standards for speed, energy economy, and scalability in next-generation computing.\u003c/p\u003e \u003cp\u003eThis gadget is the first to utilize quantum geometric phases and antiferromagnetic dynamics in a technique that results in ultra-dense crossbar structures that are impermeable to stray fields and thermal fluctuations. The van der Waals integration technique not only preserves spin coherence, but it additionally provides a possibility for adjusting interfacial exchange coupling and spin-orbit interactions at the atomic level. The AF-TSV's analog resistance states and strain-mediated switching mechanisms demonstrate that it might be used in neuromorphic computing, where synaptic plasticity and rapid inference could work together on the same platform.\u003c/p\u003e \u003cp\u003eInterfacial defect engineering, heat dissipation in ultra-scaled devices, and the combination of hybrid quantum-classical architectures are all things that future research has to look into. Looking at how topological superconductivity and antiferromagnetic order affect each other could lead to new features, including qubit interfaces that can handle errors or Majorana-based logic. In its final moments, the AF-TSV shows the capacity it is to combine ideas from many fields. It brings together condensed matter physics, materials science, and nanotechnology to make computers that use less energy, don't lose data, and work very quickly. The development of this memory technology marks the start of a new era in which quantum materials and atomic-scale design come together to comply with the needs of artificial intelligence, quantum computing, and additional information.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003cp\u003eI am ready for discussion on this paper.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eRespected sir, this is my paper. if you have to give any suggestions, it is my pleasure to discuss it.with regards.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eSierra, J. F., et al. (2021). \u003cem\u003eVan der Waals heterostructures for spintronics and opto-spintronics\u003c/em\u003e. Nature Nanotechnology, 16, 856\u0026ndash;868. DOI:10.1038/s41565-021-00936-x\u003c/li\u003e\n\u003cli\u003eZhao, Z., Lin, Y., \u0026amp; Avsar, A. 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DOI:10.1038/s41578-020-0190-0\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Vander Walls(vdW) Heterostructure, Antiferromagnetic Topological Spin Valve (AF-TSV), Antiferromagnetic (AFM), Zero-field Tunneling Magnetoresistance, Spin-transfer torque magnetic RAM (STT-MRAM), Terahertz-frequency dynamics","lastPublishedDoi":"10.21203/rs.3.rs-6734290/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6734290/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Room-Temperature Antiferromagnetic Topological Spin Valve (AF-TSV) is a new type of memory technology that uses antiferromagnetic (AFM) materials and topological quantum states in vander Waals (vdW) heterostructures[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. This device uses the interaction between spin-momentum-locked surface states and N\u0026eacute;el order dynamics by combining atomically thin AFM layers (such as FePS₃ and MnBi₂Te₄) with topological insulators (TIs) like Bi₂Se₃[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The AF-TSV works without outside magnetic fields, unlike regular ferromagnetic spin valves. Instead, it uses ultrafast spin-orbit torque (SOT)[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] switching caused by current pulses in the plane. The lack of stray fields makes it possible for ultra-dense crossbar topologies to scale down to nodes smaller than 10 nm. Defect-tolerant vdW interfaces and strong AFM order keep the system stable at ambient temperature and allow switching on the picosecond scale. Recent advances in electrically controllable exchange bias and interfacial spin transfer support the viability of experiments[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The AF-TSV bridges high-speed volatile memory and slow, durable storage. It has speeds above 100 GHz, energy efficiency below 10 fJ/bit, and it does not lose data. It is the foundation for next-generation computing, edge AI, and quantum-ready hardware.\u003c/p\u003e \u003cp\u003eThe AF-TSV study gives novel approaches to changing memory, as well as other things. By accumulating different AFM layers on top of each other in different ways (such as zigzag vs. stripy), multi-state memory cells might store more than 2 bits per cell through gate-tunable interlayer exchange coupling. By mixing TI surface states with AFM layers, it should be possible to create zero-field tunneling magnetoresistance that is more than 500%, which would allow for ultra-sensitive readout without changing the N\u0026eacute;el vector[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Adding piezoelectric vdW substrates like In₂Se₃ could make strain-mediated switching possible. In this process, uniaxial strain changes AFM anisotropy in real time to allow for voltage-controlled, ultra-low-power operation. The device's analog resistance states could help neuromorphic computing by imitating synaptic plasticity through partial N\u0026eacute;el reorientation. Picosecond switching speeds up inference workloads. Also, proximity-induced topological superconductivity at TI/AFM interfaces, through Rashba spin-orbit coupling[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], could host Majorana zero modes. This would make it possible to create hybrid memory-qubit architectures for quantum systems that can handle errors. We need to find ways to fix problems like interfacial defects, map AFM dynamics with picosecond resolution, and produce heterostructures on a wafer scale. However, these problems also bring chances for breakthroughs in ultrafast spintronics, quantum materials engineering, and energy-efficient computing[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The AF-TSV is a combination of topology, antiferromagnetism, and vdW design that is about to change the way we think about non-volatile memory and computing architectures.\u003c/p\u003e","manuscriptTitle":"Study of Vander Waals Heterostructure-Based Antiferromagnetic SpinValves for Next-Generation Memory Technology","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-09 06:05:17","doi":"10.21203/rs.3.rs-6734290/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4bae72e7-e2f7-4561-b7d8-47d32a74dfbe","owner":[],"postedDate":"June 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":49566406,"name":"Physical sciences/Materials science"},{"id":49566407,"name":"Physical sciences/Physics"}],"tags":[],"updatedAt":"2025-07-07T17:08:16+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-09 06:05:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6734290","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6734290","identity":"rs-6734290","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}