Eavesdropping on spin waves inside the domain-wall nanochannel via three-magnon processes

Beining Zhang, Zhenyu Wang, Yunshan Cao, Peng Yan, and X. R. Wang
Phys. Rev. B 97, 094421 – Published 19 March 2018

Abstract

One recent breakthrough in the field of magnonics is the experimental realization of reconfigurable spin-wave nanochannels formed by a magnetic domain wall with a width of 10–100 nm [Wagner et al., Nat. Nano. 11, 432 (2016)]. This remarkable progress enables an energy-efficient spin-wave propagation with a well-defined wave vector along its propagating path inside the wall. In the mentioned experiment, a microfocus Brillouin light scattering spectroscopy was taken in a line-scans manner to measure the frequency of the bounded spin wave. Due to their localization nature, the confined spin waves can hardly be detected from outside the wall channel, which guarantees the information security to some extent. In this work, we theoretically propose a scheme to detect/eavesdrop on the spin waves inside the domain-wall nanochannel via nonlinear three-magnon processes. We send a spin wave (ωi,ki) in one magnetic domain to interact with the bounded mode (ωb,kb) in the wall, where kb is parallel with the domain-wall channel defined as the ẑ axis. Two kinds of three-magnon processes, i.e., confluence and splitting, are expected to occur. The confluence process is conventional: conservation of energy and momentum parallel with the wall indicates a transmitted wave in the opposite domain with ω(k)=ωi+ωb and (ki+kbk)·ẑ=0, while the momentum perpendicular to the domain wall is not necessary to be conserved due to the nonuniform internal field near the wall. We predict a stimulated three-magnon splitting (or “magnon laser”) effect: the presence of a bound magnon propagating along the domain wall channel assists the splitting of the incident wave into two modes, one is ω1=ωb,k1=kb identical to the bound mode in the channel, and the other one is ω2=ωiωb with (kikbk2)·ẑ=0 propagating in the opposite magnetic domain. Micromagnetic simulations confirm our theoretical analysis. These results demonstrate that one is able to uniquely infer the spectrum of the spin wave in the domain-wall nanochannel once we know both the injection and the transmitted waves.

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  • Received 20 November 2017
  • Revised 21 January 2018

DOI:https://doi.org/10.1103/PhysRevB.97.094421

©2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsNonlinear Dynamics

Authors & Affiliations

Beining Zhang1, Zhenyu Wang1, Yunshan Cao1,*, Peng Yan1,†, and X. R. Wang2,3

  • 1School of Electronic Science and Engineering and State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
  • 2Physics Department, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
  • 3HKUST Shenzhen Research Institute, Shenzhen 518057, China

  • *Corresponding author: yunshan.cao@uestc.edu.cn
  • Corresponding author: yan@uestc.edu.cn

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Issue

Vol. 97, Iss. 9 — 1 March 2018

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