Tuning edge-localized spin waves in magnetic microstripes by proximate magnetic structures

Zhizhi Zhang, Michael Vogel, M. Benjamin Jungfleisch, Axel Hoffmann, Yan Nie, and Valentine Novosad

Phys. Rev. B 100, 174434 – Published 26 November 2019

Abstract

The propagation of edge localized spin waves (E-SWs) in yttrium iron garnet (YIG; $Y_{3} {Fe}_{5} O_{12}$ ) microstripes with and without magnetic microstructures in close proximity is investigated by micromagnetic simulations. A splitting of the dispersion curve with the presence of permalloy (Py; ${Ni}_{81} {Fe}_{19}$ ) stripe is observed. The results show that E-SWs on the two edges of YIG stripe have different wavelengths, group velocities, and decay lengths at the same frequencies. The role of the Py stripe was found to be the source of the inhomogeneous static dipolar field without dynamic coupling with YIG. This work opens new perspectives for the design of innovative spin wave interference-based logic devices.

Received 15 July 2019

DOI:https://doi.org/10.1103/PhysRevB.100.174434

Physics Subject Headings (PhySH)

Spin dynamics Spin waves Stripes

Micromagnetic modeling

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Zhizhi Zhang ^1,2, Michael Vogel¹, M. Benjamin Jungfleisch ³, Axel Hoffmann ^1,4, Yan Nie^2,*, and Valentine Novosad^1,†

¹Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
²School of Optical & Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
³Department of Physics & Astronomy, University of Delaware, Newark, Delaware 19716, USA
⁴Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

^*nieyan@hust.edu.cn
^†novosad@anl.gov

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Issue

Vol. 100, Iss. 17 — 1 November 2019

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Images

Figure 1
(a) Schematic of the proposed YIG/Py structures. The gap between the edges is $d_{gap} = 100 nm$ , and the distance from any in-plane point to the edge of the Py stripe is $r$ . The yellow antenna region indicates the SW generation. (b) Temporal evolution of sinc function field with $h_{0} = 10 Oe$ applied along $x$ axis with a Gaussian distribution centered in yellow antenna region. (c) Frequency spectrum obtained from FFT of applied sinc field with $f_{c} = 50 GHz$ .
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Figure 2
Dispersion relations for both W-SWs and E-SWs propagating in (a) single YIG stripe without Py stripe, (b) YIG stripe in YIG/Py, and (c) Py stripe in YIG/Py. $k$ is along the $x$ axis.
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Figure 3
Zoomed in dispersion diagram focused on E-SWs in (a) single YIG and (b) YIG stripe in YIG/Py. The dashed lines depict the wave vectors for specific excitation frequencies. The response of the $m_{z}$ / $M_{s}$ in (c) single YIG, (d) YIG stripe in YIG/Py at $t = 80 ns$ under 3.9 GHz excitation and (e) YIG stripe in YIG/Py at $t = 80 ns$ under 4.5 GHz excitation. Upper panels are the global 2D maps of the $m_{z}$ / $M_{s}$ intensity (green represents Py, same hereinafter); lower panels are the $m_{z}$ / $M_{s}$ intensity distribution along the two edges of YIG stripes, where the blue curves are for the edge closer to Py, the red curves are for the edge far away from Py, and the green dash curves are the envelope line obtained from the fitting. (f) The temporal evolution of $m_{z}$ / $M_{s}$ monitored at the ends of the two edges of the YIG stripe in the case of (e). Blue square and red circle dots represent the positions (10 μm away from the excitation) shown in the upper panel of (e). The yellow patch in the plot indicates the transient states, and the green patch indicates the stable states. τ is the time for the $m_{z}$ / $M_{s}$ at the positions reaching to the stable state.
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Figure 4
The $y$ component of $H_{eff}$ across (a) single YIG stripe and (b) YIG stripe and Py stripe in YIG/Py under 1000 Oe.
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Figure 5
(a) Profile of the $y$ component $H_{dip - Py}$ versus the distance to the fully magnetized Py stripe. (b) The dispersion relations of the SWs propagating in YIG stipes in YIG/Py with $d_{gap} = 200$ and 1000 nm, respectively.
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Figure 6
(a) 2D maps of the $m_{z}$ / $M_{s}$ intensity of the YIG stripe ( $f = 4.5 GHz$ and $t = 80 ns$ ) under the static external field consisting of the 1000 Oe homogeneous field and the inhomogeneous field aligned perpendicular to the long side of the stripe, as described by Eq. (3) with $n = 1$ . (b) The temporal evolution of $m_{z}$ / $M_{s}$ monitored at the end of the YIG stripe. Blue square and red circle dots represent the corresponding positions shown in (a).
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