Propagation of Spin Waves in Intersecting Yttrium Iron Garnet Nanowaveguides

D. Raskhodchikov, J. Bensmann, K.O. Nikolaev, E. Lomonte, L. Jin, P. Steeger, J.A. Preuß, R. Schmidt, R. Schneider, J. Kern, S. Michaelis de Vasconcellos, R. Bratschitsch, S.O. Demokritov, W.H.P. Pernice, and V.E. Demidov

Phys. Rev. Applied 18, 054081 – Published 28 November 2022

Abstract

We study experimentally the propagation of spin waves in waveguide structures consisting of two submicrometer-width yttrium iron garnet waveguides intersecting at a right angle. We show that, despite the significant spatial variations of the internal static magnet field and the in-plane anisotropy of the dispersion characteristics, the incident spin wave can efficiently pass through the microscopic cross-shaped structure and be transmitted into all its arms. This process depends strongly on the frequency of the wave and the orientation of the static magnetic field. By varying these parameters, one can achieve a controllable uniform or preferential transmission of the wave into different arms of the cross. Our results create the basis for the implementation of nanoscale magnonic networks to be used for the realization of complex non-Boolean data-processing schemes, including neuromorphic computing.

Received 26 July 2022
Accepted 28 September 2022

DOI:https://doi.org/10.1103/PhysRevApplied.18.054081

Physics Subject Headings (PhySH)

Magnetization dynamics Spin dynamics Spin waves Spintronics Waveguides

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

D. Raskhodchikov ^1,†, J. Bensmann ^1,†, K.O. Nikolaev ^2,†, E. Lomonte¹, L. Jin ¹, P. Steeger ¹, J.A. Preuß ¹, R. Schmidt¹, R. Schneider¹, J. Kern¹, S. Michaelis de Vasconcellos ¹, R. Bratschitsch ¹, S.O. Demokritov ², W.H.P. Pernice ^1,3, and V.E. Demidov ^2,*

¹Institute of Physics, Center for Nanotechnology and Center for Soft Nanoscience, University of Muenster, 48149 Muenster, Germany
²Institute of Applied Physics, University of Muenster, 48149 Muenster, Germany
³Kirchhoff-Institute for Physics, Heidelberg University, 69120 Heidelberg, Germany

^*demidov@uni-muenster.de
^†These authors contributed equally to this work.

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Vol. 18, Iss. 5 — November 2022

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Images

Figure 1
Schematics of the experiment. Studied structures consist of two 800-nm-wide and 120-nm-thick YIG stripe waveguides (marked as WG1 and WG2) intersecting at a right angle. Spin waves are excited in waveguide WG1 using a 150-nm-thick and 500-nm-wide $Au$ antenna, located at a distance of 5 μm from the intersection. Structure is magnetized by the static magnetic field, H₀, applied in the sample plane at angle φ relative to the axis of the antenna. Propagation of spin waves is visualized using microfocus BLS spectroscopy.
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Figure 2
(a)–(d) Representative spatial maps of spin-wave intensity recorded at different excitation frequencies, as labeled. (e) Frequency dependence of transmission coefficients T₁₂ and T₁₃ defined as the ratio of the intensities of the waves detected at spatial points P1–P3 located in different arms of the cross, as shown in (a). Data are obtained at H₀= 1.0 kOe and φ = 0.
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Figure 3
(a) Calculated spatial profiles of the internal static magnetic field, H_int, along the axes of the two waveguides, as shown in the inset. (b),(c) Calculated dispersion curves of spin waves in WG1 and WG2 (solid curves). Horizontal dashed line in (b) marks the estimated cutoff frequency, f_c, of the DE waves in the intersection region. Insets in (c) schematically illustrate the distributions of the dynamic magnetization in the transverse section of the waveguide corresponding to the shown BV modes. Arrows illustrate the transformation of DE waves in WG1 into BV waves in WG2. Data are obtained at H₀= 1.0 kOe and φ = 0.
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Figure 4
(a) Spatial maps of the spin-wave intensity recorded at different excitation frequencies, as labeled. (b) Frequency dependence of the spatial period of the snakelike pattern obtained from the Fourier analysis of the measured maps (symbols) together with the dependence obtained from the analysis of the calculated dispersion spectra (solid curve). Data are obtained at H₀= 1.0 kOe and φ = 0.
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Figure 5
(a)–(d) Spatial maps of the spin-wave intensity recorded at different angles of the static magnetic field, φ, as labeled. Data are obtained at H₀= 1.0 kOe and f = 4.5 GHz. (e) Angular dependence of the transmission coefficients T₁₂ and T₁₃. Squares and solid lines show data obtained at f = 4.5 GHz. Circles and dashed lines show data obtained at f = 4.8 GHz.
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Figure 6
(a) Calculated spatial profiles of the internal static magnetic field, H_int, along the axes of the two waveguides, as shown in the inset. Calculations are performed at H₀= 1.0 kOe and φ = 30°. (b)–(d) Snapshots of the normalized out-of-plane magnetization component obtained from micromagnetic simulations of spin-wave propagation. Spin waves are excited by applying a localized dynamic magnetic field with a frequency of 4.5 GHz. (b),(c) Complete cross structure magnetized at φ = 10 and 30°, respectively. (d) Single waveguide magnetized at φ = 30°.
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