Abstract
Spin-Hall oscillators (SHO) are promising sources of spin-wave signals for magnonics applications, and can serve as building blocks for magnonic logic in ultralow power computation devices. Thin magnetic layers used as “free” layers in SHO are in contact with heavy metals having large spin-orbital interaction, and, therefore, could be subject to the spin-Hall effect (SHE) and the interfacial Dzyaloshinskii-Moriya interaction (i-DMI), which may lead to the nonreciprocity of the excited spin waves and other unusual effects. Here, we analytically and micromagnetically study magnetization dynamics excited in an SHO with oblique magnetization when the SHE and i-DMI act simultaneously. Our key results are: (i) excitation of nonreciprocal spin-waves propagating perpendicularly to the in-plane projection of the static magnetization; (ii) skyrmions generation by pure spin-current; (iii) excitation of a new spin-wave mode with a spiral spatial profile originating from a gyrotropic rotation of a dynamical skyrmion. These results demonstrate that SHOs can be used as generators of magnetic skyrmions and different types of propagating spin-waves for magnetic data storage and signal processing applications.
Highlights
Spin-orbitronics combined with other sub-fields of spintronics, such as magnonics and spin-caloritronics, has created a novel paradigm in information processing which could become a viable alternative to Si-based electronics[1]
Seven different regions can be distinguished in this phase diagram: uniform states (US), Slonczewski linear modes (SLM), spiral modes (SpM), skyrmions (SKY), and the bistability regions uniform states/skyrmions (US/SKY), Slonczewski linear modes/spiral modes (SLM/SpM) and Slonczewski linear modes/skyrmions (SLM/SKY)
DC is the critical value of the interfacial Dzyaloshinskii-Moriya interaction (i-DMI) parameter, Ith is the threshold current, Isky is the current needed to nucleate skyrmions; (d) Comparison between the threshold current of the SLM excitation obtained by means of micromagnetic simulations and using the analytical formula (3)
Summary
Spin-orbitronics combined with other sub-fields of spintronics, such as magnonics and spin-caloritronics, has created a novel paradigm in information processing which could become a viable alternative to Si-based electronics[1]. Micromagnetic simulations have demonstrated that (i) a novel propagating spin-wave mode, characterized by a spiral spatial profile, can be excited at sufficiently large magnitudes of D and I, and (ii) skyrmions can be efficiently nucleated by the SHE in the SHO geometry.
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