Fabrication of voltage-gated spin Hall nano-oscillators

Kumar, Akash; Rajabali, Mona; González, Víctor H.; Zahedinejad, Mohammad; Houshang, Afshin; Åkerman, Johan

doi:10.1039/d1nr07505e

Cited by 26 publications

(16 citation statements)

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“…The samples were then coated with 40 nm of hydrogen silsesquioxane (HSQ) negative tone electron beam resist. The SHNO chains used in the experiments were then fabricated using a combination of e-beam lithography (Raith EBPG 5200) and Ar-ion etching: more details can be found in ref . The top contact pads are fabricated using laser writing-based direct lithography followed by deposition of Cu(800 nm)/Pt(20 nm) thin films for the Ground-Signal-Ground coplanar waveguide.…”

Section: Methodsmentioning

confidence: 99%

“…In this work, we study mutual synchronization in much longer SHNO chains of up to 50 serially connected nanoconstrictions fabricated from W(5 nm)/CoFeB(1.4 nm)/MgO(2 nm), − W(5 nm)/NiFe(3 nm), and NiFe(5 nm)/Pt(5 nm) , material stacks (the order represents the actual stack sequence), focusing primarily on the W based SHNOs with their much lower threshold current and lower line width compared to Pt based systems (due to reduced spin pumping and lower inverse spin Hall effect). We find that robust and complete mutual synchronization can persist in chains of up to 21 oscillators, resulting in 1/ N reduction in line width and N 2 enhanced output peak power compared to single SHNOs.…”

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confidence: 99%

“…The mutual synchronization of these oscillators in a chain can be explored for bioinspired computing and beyond ,, where each oscillator behaves as a neuron. Combined with voltage ,, and/or memristive control of synchronization (synaptic weights), these large chains can be used to locally or globally control the coupling between oscillators (neurons). The present work also serves as a stepping stone in the direction toward further scaling mutual synchronization to much larger square or rectangular arrays well beyond the previously demonstrated 64 oscillators.…”

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confidence: 99%

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Robust Mutual Synchronization in Long Spin Hall Nano-oscillator Chains

et al. 2023

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Mutual synchronization of N serially connected spintronic nano-oscillators boosts their coherence by N and peak power by N 2. Increasing the number of synchronized nano-oscillators in chains holds significance for improved signal quality and emerging applications such as oscillator based unconventional computing. We successfully fabricate spin Hall nano-oscillator chains with up to 50 serially connected nanoconstrictions using W/NiFe, W/CoFeB/MgO, and NiFe/Pt stacks. Our experiments demonstrate robust and complete mutual synchronization of 21 nanoconstrictions at an operating frequency of 10 GHz, achieving line widths <134 kHz and quality factors >79,000. As the number of mutually synchronized oscillators increases, we observe a quadratic increase in peak power, resulting in 400-fold higher peak power in long chains compared to individual nanoconstrictions. While chains longer than 21 nanoconstrictions also achieve complete mutual synchronization, it is less robust, and their signal quality does not improve significantly, as they tend to break into partially synchronized states.

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Robust Mutual Synchronization in Long Spin Hall Nano-oscillator Chains

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“…[ 39 ] Recently, they further studied mutual synchronization in much longer SHNO chains of up to 50 serially connected nano‐constrictions. [ 40 ] They found that robust and complete mutual synchronization can persist in chains of only up to 21 oscillators, resulting in a significantly lower linewidth and higher output power. For synaptic functionalities, magnetic DW devices are the most‐studied spintronic device, owing to its linear magnetization dynamics.…”

Section: Spintronic Devices For Neuromorphic Applicationsmentioning

confidence: 99%

Spintronic Heterostructures for Artificial Intelligence: A Materials Perspective

Maddu

Kumar

Bhatti

et al. 2023

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With the advent of the Big Data era, neuromorphic computing (NC) (also known as brain‐inspired computing) has gained a lot of research interest. Spintronic devices are the emerging candidates for implementing the NC due to their intrinsic nonvolatility, extremely high endurance, low‐power consumption, and complementary metal‐oxide compatibility. Many research groups have proposed various NC architectures based on spintronic devices. Herein, a collective survey of different spintronic‐based approaches is given for NC. The reviewed approaches include the progress of stochastic magnetic tunnel junction (MTJ) devices, spin‐torque nano‐oscillator, spin‐Hall nano‐oscillator, domain walls, and skyrmion devices. In all of these approaches, spin–orbit torque (SOT)‐based magnetization control, which is achieved via spintronics heterostructures, plays a significant role. Various heterostructures of heavy metal and ferromagnetic layers that have been proposed are reviewed for generating SOT. In addition, the phenomena and materials involved in the generation of orbital torque are summarized due to the orbital Hall effect (OHE), which has recently gained researchers’ attention. Finally, an outlook on the opportunities and challenges for spintronic‐based NC hardware is provided, shedding light on its great potential for artificial intelligence (AI) applications.

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“…Spin-orbit torques (SOTs) in ferromagnetic/heavy metal (FM/HM) heterostructures have emerged as a powerful tool for a wide range of spintronic applications. [1][2][3][4][5][6] Large anti-damping SOTs are of utmost interest and play a pivotal role in ultrafast magnetization switching, [3,7] spintronic oscillators, [4,6,[8][9][10] as well as the emerging area of spintronic-based neuromorphic computing. [11][12][13][14][15] In the FM/HM system, the SOT is generated either via the spin Hall effect [16][17][18][19] from the HM layer and/or the Rashba-Edelstein effect [20,21] from the interface between the DOI: 10.1002/qute.202300092 FM and HM layers.…”

Section: Introductionmentioning

confidence: 99%

Interfacial Origin of Unconventional Spin‐Orbit Torque in Py/γ−$\gamma -$IrMn₃

et al. 2023

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Angle‐resolved spin‐torque ferromagnetic resonance measurements are carried out in heterostructures consisting of Py (Ni81Fe19) and a noncollinear antiferromagnetic quantum material γ−$\gamma -$IrMn3. The structural characterization reveals that γ−$\gamma -$IrMn3 is polycrystalline in nature. A large exchange bias of 158 Oe is found in Py/γ−$\gamma -$IrMn3 at room temperature, while γ−$\gamma -$IrMn3/Py and Py/Cu/γ−$\gamma -$IrMn3 exhibit no exchange bias. Regardless of the exchange bias and stacking sequence, a substantial unconventional out‐of‐plane anti‐damping torque is observed when γ−$\gamma -$IrMn3 is in direct contact with Py. The magnitude of the out‐of‐plane spin‐orbit torque efficiency is found to be twice as large as the in‐plane spin‐orbit torque efficiency. The unconventional spin‐orbit torque vanishes when a Cu spacer is introduced between Py and γ−$\gamma -$IrMn3, indicating that the unconventional spin‐orbit torque in this system originates at the interface. These findings are important for realizing efficient antiferromagnet‐based spintronic devices via interfacial engineering.

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Fabrication of voltage-gated spin Hall nano-oscillators

Abstract: We demonstrate an optimized fabrication process for electric field (voltage gate) controlled nano-constriction spin Hall nano-oscillators (SHNOs), achieving feature sizes of <30 nm with easy to handle ma-N 2401 e-beam...

Cited by 26 publications

References 57 publications

Robust Mutual Synchronization in Long Spin Hall Nano-oscillator Chains

Robust Mutual Synchronization in Long Spin Hall Nano-oscillator Chains

Spintronic Heterostructures for Artificial Intelligence: A Materials Perspective

Interfacial Origin of Unconventional Spin‐Orbit Torque in Py/γ−$\gamma -$IrMn₃

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Fabrication of voltage-gated spin Hall nano-oscillators

Abstract: We demonstrate an optimized fabrication process for electric field (voltage gate) controlled nano-constriction spin Hall nano-oscillators (SHNOs), achieving feature sizes of <30 nm with easy to handle ma-N 2401 e-beam...

Cited by 26 publications

References 57 publications

Robust Mutual Synchronization in Long Spin Hall Nano-oscillator Chains

Robust Mutual Synchronization in Long Spin Hall Nano-oscillator Chains

Spintronic Heterostructures for Artificial Intelligence: A Materials Perspective

Interfacial Origin of Unconventional Spin‐Orbit Torque in Py/γ−$\gamma -$IrMn3

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Product

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Interfacial Origin of Unconventional Spin‐Orbit Torque in Py/γ−$\gamma -$IrMn₃