Ultra-low-current-density single-layer magnetic Weyl semimetal spin Hall nano-oscillators

Abstract

Topological quantum materials can exhibit unconventional surface states and anomalous transport properties. Still, their applications in spintronic devices are restricted as they require the growth of high-quality thin films with bulk-like properties. Here, we study 10--30 nm thick epitaxial ferromagnetic Co${}_2$MnGa films with high structural order and very high values of the anomalous Hall conductivity, ${\sigma }_{\mathrm{xy}}=1.35\times 10^5$ ${\Omega }^{-1}{m}^{-1}$ and the anomalous Hall angle, ${\theta }_{\mathrm{H}}=15.8\%$, both comparable to bulk values. We observe a dramatic crystalline orientation dependence of the Gilbert damping constant of a factor of two and a giant intrinsic spin Hall conductivity, ${\sigma }_{\mathrm{SHC}}=(6.08\pm 0.02)\times 10^5$ ($\hslash /2e$) ${\Omega }^{-1}{m}^{-1}$, an order of magnitude higher than literature values of multilayer Co${}_2$MnGa stacks [1-3] and single-layer Ni, Co, Fe [4], and Ni${}_{80}$Fe${}_{20}$~[4,5]. As a consequence, spin-orbit-torque driven auto-oscillations of a 30 nm thick magnetic film are observed for the first time, at an ultralow threshold current density of $J_{th}=6.2\times 10^{11}$ $A{m}^{-2}$. Theoretical calculations of the intrinsic spin Hall conductivity, originating from a strong Berry curvature, corroborate the results and yield values comparable to the experiment. Our results open up for the design of spintronic devices based on single layers of magnetic topological quantum materials.

19 pages

References in corpus (17)

• Magnetic Weyl Semimetal Phase in a Kagome Crystal
• Study of Intrinsic Spin Hall Effect and Orbital Hall Effect in 4d- and 5d- Transition Metals
• Discovery of topological Weyl fermion lines and drumhead surface states in a room temperature magnet
• Topological Hopf and chain link semimetal states and their application to Co2MnGa (Theory and Materials Prediction)
• Fermi level tuning and atomic ordering induced giant anomalous Nernst effect in Co2MnAl1-xSix Heusler alloy
• Memristive control of mutual SHNO synchronization for neuromorphic computing
• Spin-polarized Weyl cones and gigantic anomalous Nernst effect in ferromagnetic Heusler films
• Giant voltage control of spin Hall nano-oscillator damping
• Thickness dependent tuning of the Berry curvature in a ferromagnetic Weyl semimetal
• Magnetization switching induced by spin-orbit torque from Co2MnGa magnetic Weyl semimetal thin films
• Robust mutual synchronization in long spin Hall nano-oscillator chains
• Ultrathin ferrimagnetic GdFeCo films with very low damping
• Gate-Tunable Berry Curvature Dipole Polarizability in Dirac Semimetal Cd3As2
• Spin wave-driven variable-phase mutual synchronization in spin Hall nano-oscillators
• Gigantic Anisotropy of Self-Induced Spin-Orbit Torque in Weyl Ferromagnet Co2MnGa
• Phase noise analysis of mutually synchronized spin Hall nano-oscillators
• Mutual synchronization in spin torque and spin Hall nano-oscillators

Cited by in corpus (1)

• Energy-efficient spin Hall nano-oscillators using near-compensated CoGd ferrimagnets