Robust Mutual Synchronization in Long Spin Hall Nano-oscillator Chains

Abstract

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.

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

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