Research Project: Ultralow power and ultra-wideband spintronics near thermodynamic limits
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Contributors
Funders
ID
EC.00141
Authors
Onbaşlı, Mehmet Cengiz
Faculty Member
Publications
Stabilization and adiabatic control of antiferromagnetically coupled skyrmions without the topological hall effect
(Royal Soc Chemistry, 2023) Cheghabouri, Arash Mousavi; Onbaşlı, Mehmet Cengiz; Yağan, Rawana; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Synthetic antiferromagnetically coupled (SAF) multilayers provide different physics of stabilizing skyrmions while eliminating the topological Hall effect (THE), enabling efficient and stable control. The effects of material parameters, external current drive, and a magnetic field on the skyrmion equilibrium and propagation characteristics are largely unresolved. Here, we present a computational and theoretical demonstration of the large window of material parameters that stabilize SAF skyrmions determined by saturation magnetization, uniaxial anisotropy, and Dzyaloshinskii-Moriya interaction. Current-driven SAF skyrmion velocities reach & SIM;200 m s(-1) without the THE. The SAF velocities are about 3-10 times greater than the typical ferromagnetic skyrmion velocities. The current densities needed for driving SAF skyrmions could be reduced to 10(8) A m(-2), while 10(11) A m(-2) or above is needed for ferromagnetic skyrmions. By reducing the SAF skyrmion drive current by 3 orders, Joule heating is reduced by 6 orders of magnitude. These results pave the way for new SAF interfaces with improved equilibrium, dynamics, and power savings in THE-free skyrmionics.
Interface-induced stability of nontrivial topological spin textures: unveiling room-temperature hopfions and skyrmions
(Wiley-V C H Verlag Gmbh, 2025) Yağan, Rawana; Cheghabouri, Arash Mousavi; Onbaşlı, Mehmet Cengiz; Cheghabouri, Arash Mousavi; Yağan, Rawana; Katmis, Ferhat; Lauter, Valeria; Brandt, Iuri S.; Zhou, Hua; Freeland, John W.; de Araujo, Clodoaldo I. L.; Jamer, Michelle E.; Heiman, Don; Moodera, Jagadeesh S.; Department of Electrical and Electronics Engineering; Department of Physics; Yes; College of Engineering; College of Sciences
Topological spin configurations, such as soliton-like spin texture and Dirac electron assemblies, have recently emerged in fundamental science and technology. Achieving stable topological spin textures at room temperature is crucial for their use as long-range information carriers. However, their creation and manipulation are hindered by multi-step field training and competing interactions. Thus, a spontaneous ground state for multidimensional topological spin textures is desirable, with skyrmions forming swirling, hedgehog-like spin structures in two dimensions and hopfions as their twisted 3D counterparts. Here, the first observation of robust and reproducible topological spin textures of hopfions and skyrmions observed at room temperature and in zero magnetic field is reported, which are stabilized by geometric confinement and protected by interfacial magnetism in a ferromagnet/topological insulator/ferromagnet trilayer heterostructure. These skyrmion-hopfion configurations are directly observed at room temperature with Lorenz transmission electron microscopy. Using micromagnetic modeling, the experimental observations of hopfion-skyrmion assemblies are reproduced. This model reveals a complete picture of how spontaneously organized skyrmion lattices encircled by hopfion rings are controlled by surface electrons, uniaxial anisotropy, and Dzyaloshinskii-Moriya interaction. This study provides evidence that topological chiral spin textures can facilitate the development of magnetic topological carriers, paving the way for ultralow-power and high-density information processing.
Cascadable direct current driven skyrmion logic inverter gate
(American Physical Society (APS), 2022) Onbaşlı, Mehmet Cengiz; Cheghabouri, Arash Mousavi; Katmış, Ferhat; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Nanoscale skyrmions enable ultralow-power nonvolatile logic gate designs due to their current-driven motion and topological protection. A key building block in skyrmion-based digital spintronics is the logic inverter (NOT) gate. Despite recent computational and practical demonstrations, a skyrmion-based low-power, wideband, and cascadable inverter gate is still a long way off. For skyrmion-based logic circuits, a systematic design and analysis of an inverter gate is essential. Here we present a skyrmion logic inverter design and analyze its full operation using micromagnetic modeling. Because of the substrate thermal conductivity, our investigations reveal that the all-metallic inverter gate can function with direct current drive, wide bandwidth, submicron footprint, no or low external magnetic field, cascadability, and with room-temperature thermal stability despite Joule heating. Using magnetic insulators for eliminating Joule heating and lowering the exchange stiffness, magnetic moment and other factors might further assist in reducing power consumption by more than four orders of magnitude.
Quantifying polycrystallinity effects on skyrmion dynamics and device performance
(Royal Society of Chemistry, 2025) Cheghabouri, Arash Mousavi; Onbaşlı, Mehmet Cengiz; Cheghabouri, Arash Mousavi; Trabzon, Ahmet Bahadır; Department of Physics; Department of Electrical and Electronics Engineering; Yes; College of Sciences; College of Engineering
Skyrmion-based devices promise energy-efficient spintronic functionalities, but polycrystalline magnetic films can degrade performance by inducing skyrmion pinning. Here, we use micromagnetic modeling to quantify the impact of polycrystallinity-induced variability in key material parameters such as saturation magnetization, Dzyaloshinskii–Moriya interaction, and uniaxial anisotropy on skyrmion stability, dynamics, and hysteresis loops in Co/Pt films and device geometries. We demonstrate that variations exceeding 5% in these parameters across grains significantly increase the likelihood of pinning, with the effects depending on both grain size and distribution. Our findings establish quantitative tolerance thresholds and highlight the importance of fabricating films with narrow grain size distributions and stringent control over material uniformity to enable robust, pinning-free operation in skyrmion-based spintronic devices.
Universal skyrmion logic gates and circuits based on antiferromagnetically coupled skyrmions without a topological Hall effect
(Royal Society of Chemistry, 2024) Onbaşlı, Mehmet Cengiz; Yağan, Rawana; Cheghabouri, Arash Mousavi; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Nanoscale skyrmions are spin-based quasiparticles that are promising for nonvolatile logic applications. However, the presence of the skyrmion Hall effect (SkHE) in ferromagnetic skyrmions limits their performance in logic devices. Here, we present a detailed micromagnetic modeling study on low-energy skyrmion logic gate circuits based on skyrmions in synthetic antiferromagnetically coupled (SAF) metallic ferromagnetic layers to eliminate the SkHE while reducing current requirements. First, we demonstrate the functionalities of the SAF skyrmion logic inverter gate and other Boolean gates such as NOR, OR, AND, and NAND using the inverter gate block and show the improved performance over their ferromagnetic skyrmion gate counterparts. We analyzed the operation and energy consumption at different stages of the SAF skyrmion logic operation and found that the SAF gates can operate at lower current densities. We designed a multiplexer circuit as a test case and obtained a fast response and low Joule heating. The skyrmion motion through the gates is shown to be stable and efficient in different regions, and cascading the gates creates longer linear motion without the unwanted transverse SkHE. Overall, the results indicate the feasibility of antiferromagnetically coupled skyrmions for low-energy logic with improved performance over ferromagnetic skyrmionics.
