| 1. |
- Chumak, A. V., et al.
(author)
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Advances in Magnetics Roadmap on Spin-Wave Computing
- 2022
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In: IEEE Transactions on Magnetics. - 0018-9464. ; 58:6
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Journal article (peer-reviewed)abstract
- Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction. Author
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| 2. |
- Behera, Nilamani, et al.
(author)
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Energy-Efficient W100-xTax/ Co-Fe-B/MgO Spin Hall Nano-Oscillators
- 2022
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In: Physical Review Applied. - 2331-7019. ; 18:2
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Journal article (peer-reviewed)abstract
- We investigate a W-Ta alloying route to reduce the auto-oscillation threshold current densities and the power consumption of nanoconstriction based spin Hall nano-oscillators. Using spin-torque ferromagnetic resonance measurements on microbars of W100-xTax(5 nm)/Co-Fe-B(t)/MgO stacks with t=1.4, 1.8, and 2.0 nm, we measure a substantial improvement in both the spin-orbit torque efficiency and the spin Hall conductivity. We demonstrate a 34% reduction in auto-oscillation threshold current density, which translates into a 64% reduction in power consumption as compared with pure W-based spin Hall nano-oscillators. Our work demonstrates the promising aspects of W-Ta alloying for the energy-efficient operation of emerging spintronic devices.
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| 3. |
- Fulara, Himanshu, et al.
(author)
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Giant voltage-controlled modulation of spin Hall nano-oscillator damping
- 2020
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Journal article (peer-reviewed)abstract
- Spin Hall nano-oscillators (SHNOs) are emerging spintronic devices for microwave signal generation and oscillator-based neuromorphic computing combining nano-scale footprint, fast and ultra-wide microwave frequency tunability, CMOS compatibility, and strong non-linear properties providing robust large-scale mutual synchronization in chains and two-dimensional arrays. While SHNOs can be tuned via magnetic fields and the drive current, neither approach is conducive to individual SHNO control in large arrays. Here, we demonstrate electrically gated W/CoFeB/MgO nano-constrictions in which the voltage-dependent perpendicular magnetic anisotropy tunes the frequency and, thanks to nano-constriction geometry, drastically modifies the spin-wave localization in the constriction region resulting in a giant 42% variation of the effective damping over four volts. As a consequence, the SHNO threshold current can be strongly tuned. Our demonstration adds key functionality to nano-constriction SHNOs and paves the way for energy-efficient control of individual oscillators in SHNO chains and arrays for neuromorphic computing. Spin Hall nano-oscillators can be tuned via magnetic fields and the drive current, but individual oscillator control in large arrays remains a challenge. Here, the authors provide individual control of the threshold current and the auto-oscillation frequency by voltage-controlled magnetic anisotropy.
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| 4. |
- Kumar, Akash, et al.
(author)
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Robust Mutual Synchronization in Long Spin Hall Nano-oscillator Chains
- 2023
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In: Nano Letters. - 1530-6984. ; 23:14, s. 6720-6726
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Journal article (peer-reviewed)abstract
- Mutual synchronizationof N serially connectedspintronic nano-oscillators boosts their coherence by N and peak power by N (2). Increasing thenumber of synchronized nano-oscillators in chains holds significancefor improved signal quality and emerging applications such as oscillatorbased unconventional computing. We successfully fabricate spin Hallnano-oscillator chains with up to 50 serially connected nanoconstrictionsusing W/NiFe, W/CoFeB/MgO, and NiFe/Pt stacks. Our experiments demonstraterobust and complete mutual synchronization of 21 nanoconstrictionsat an operating frequency of 10 GHz, achieving line widths 79,000. As the number of mutually synchronizedoscillators increases, we observe a quadratic increase in peak power,resulting in 400-fold higher peak power in long chains compared toindividual nanoconstrictions. While chains longer than 21 nanoconstrictionsalso achieve complete mutual synchronization, it is less robust, andtheir signal quality does not improve significantly, as they tendto break into partially synchronized states.
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| 5. |
- Rajabali, Mona, et al.
(author)
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Injection Locking of Linearlike and Soliton Spin-Wave Modes in Nanoconstriction Spin Hall Nano-oscillators
- 2023
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In: Physical Review Applied. - 2331-7019. ; 19:3
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Journal article (peer-reviewed)abstract
- We study injection locking of two different spin wave (SW) modes (a field-localized linearlike interior mode and a self-localized SW bullet soliton) in a single nanoconstriction-based spin Hall nano-oscillator. Mode selection is achieved by varying the oblique magnetic field angle and magnitude. The two modes show dramatically different responses to injection locking, in terms of locking bandwidth and linewidth and output power in the locked state. Extracting the locking range graphically from the experimental data yields apparent thresholds for the required injected power, with the bullet mode showing a larger threshold than the linearlike mode. By instead fitting the full detuning behavior using a model including thermal noise, the apparent threshold vanishes, while the very different locking behavior of the two modes can instead be ascribed to the order of magnitude difference in their mode volumes.
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| 6. |
- Zahedinejad, Mohammad, 1986, et al.
(author)
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Memristive control of mutual spin Hall nano-oscillator synchronization for neuromorphic computing
- 2022
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In: Nature Materials. - : Springer Nature. - 1476-1122 .- 1476-4660. ; 21:1, s. 81-87
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Journal article (peer-reviewed)abstract
- Synchronization of large spin Hall nano-oscillator (SHNO) arrays is an appealing approach toward ultrafast non-conventional computing. However, interfacing to the array, tuning its individual oscillators and providing built-in memory units remain substantial challenges. Here, we address these challenges using memristive gating of W/CoFeB/MgO/AlOx-based SHNOs. In its high resistance state, the memristor modulates the perpendicular magnetic anisotropy at the CoFeB/MgO interface by the applied electric field. In its low resistance state the memristor adds or subtracts current to the SHNO drive. Both electric field and current control affect the SHNO auto-oscillation mode and frequency, allowing us to reversibly turn on/off mutual synchronization in chains of four SHNOs. We also demonstrate that two individually controlled memristors can be used to tune a four-SHNO chain into differently synchronized states. Memristor gating is therefore an efficient approach to input, tune and store the state of SHNO arrays for non-conventional computing models.
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