Magnon transport in ${Y}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}/\mathrm{Pt}$ nanostructures with reduced effective magnetization

Letter

Magnon transport in $Y_{3} {Fe}_{5} O_{12} / Pt$ nanostructures with reduced effective magnetization

J. Gückelhorn, T. Wimmer, M. Müller, S. Geprägs, H. Huebl, R. Gross, and M. Althammer

Phys. Rev. B 104, L180410 – Published 29 November 2021

Abstract

For applications making use of magnonic spin currents damping effects, which decrease the spin conductivity, have to be minimized. We here investigate the magnon transport in a yttrium iron garnet thin film with strongly reduced effective magnetization. We show that in a three-terminal device the effective magnon conductivity can be increased by a factor of up to six by a current applied to a modulator electrode, which generates damping compensation above a threshold current. Moreover, we find a linear dependence of this threshold current on the applied magnetic field. We can explain this behavior by the reduced effective magnetization and the associated nearly circular magnetization precession.

Received 23 July 2021
Revised 5 November 2021
Accepted 5 November 2021

DOI:https://doi.org/10.1103/PhysRevB.104.L180410

Physics Subject Headings (PhySH)

Magnetism Magnons Spintronics

Ferrimagnets Ferromagnets Magnetic systems Nanostructures Thin films

Film deposition Magnetic techniques Sputtering Transport techniques

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

J. Gückelhorn ^1,2,*, T. Wimmer^1,2, M. Müller ^1,2, S. Geprägs ¹, H. Huebl ^1,2,3, R. Gross ^1,2,3, and M. Althammer ^1,2,†

¹Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
²Physik-Department, Technische Universität München, 85748 Garching, Germany
³Munich Center for Quantum Science and Technology (MCQST), D-80799 München, Germany

^*janine.gueckelhorn@wmi.badw.de
^†matthias.althammer@wmi.badw.de

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Vol. 104, Iss. 18 — 1 November 2021

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Figure 1
(a) Sketch of the ellipticity of the magnetization precession in YIG thin films grown on lattice-matched GGG. (b) In biaxially strained YIG thin films grown on YSGG, the ellipticity is minimized due to the reduced effective magnetization. (c) X-ray diffraction of a $12.3 n m$ thick YIG film grown on a (111)-oriented YSGG substrate. The blue vertical line marks the calculated $2 θ$ -position of the (444) reflection of bulk YIG. (d) Resonance field $H_{res}$ and linewidth $Δ H$ extracted from FMR measurements of the YIG film on YSGG as a function of frequency. Via a Kittel fit (gray line) we extract $μ_{0} M_{eff} = 56 \pm 0.2 m T$ and from a linear fit to the linewidth (blue line) we obtain $μ_{0} δ H = (3.6 \pm 0.4) mT$ and $α_{G} = (1.5 \pm 0.2) \times 10^{- 3}$ .
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Figure 2
(a) Sketch of the sample configuration with the electrical connection scheme, and the coordinate system with the in-plane rotation angle $φ$ of the applied magnetic field $μ_{0} H$ . (b) Detector signal $V_{SHE}^{\det}$ plotted versus the magnetic field orientation $φ$ for different magnetic field magnitudes $μ_{0} H$ . The red line is a fit to $A_{SHE}^{\det} {cos}^{2} (φ)$ . (c) The voltage amplitudes $A_{SHE}^{\det}$ , as indicated in (b), plotted versus the distance $d_{c}$ for different magnetic fields on a logarithmic scale. The red lines correspond to exponential fits to the data points for $d_{c} \geq 1 μ m$ . (d) Extracted magnon spin diffusion lengths $λ_{m}$ from the exponential fits in (c) for different magnetic field magnitudes $μ_{0} H$ . The red line is a fit to Eq. (2), resulting in a magnon diffusion constant $D = (1.75 \pm 0.05) \times 10^{- 4} m^{2} / s$ .
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Figure 3
(a) Sketch of the sample configuration for a three-terminal device with the electrical connection scheme, and the coordinate system with the in-plane rotation angle $φ$ of the applied magnetic field $μ_{0} H$ . (b) Detector signal $V_{1 ω}^{\det}$ of a structure with $d_{e} = 200 n m$ and $w_{\mod} = 400 n m$ plotted versus the magnetic field orientation with constant magnitude $μ_{0} H = 50 m T$ for various modulator currents $I_{dc}^{\mod}$ . (c) The voltage amplitudes $A_{1 ω}^{\det}$ , as indicated in (b), versus the DC charge current $I_{dc}^{\mod}$ . The gray lines indicate fits to Eq. (3) for current values below the threshold current.
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Figure 4
Extracted critical currents $I_{crit}^{\mod}$ , as indicated by the black triangles in Fig. 3, as a function of the magnetic field magnitude $μ_{0} H$ (blue circles). For comparison, the black data points are taken from our previous work, where we investigate an YIG thin film grown on lattice-matched GGG substrates [10]. The dashed lines correspond to fits to Eq. (4) with a finite $M_{eff}$ , while the solid line is a fit to the data in the limit of $M_{eff} = 0$ .
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Physical Review B

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Magnon transport in $Y_{3} {Fe}_{5} O_{12} / Pt$ nanostructures with reduced effective magnetization

J. Gückelhorn, T. Wimmer, M. Müller, S. Geprägs, H. Huebl, R. Gross, and M. Althammer

Phys. Rev. B 104, L180410 – Published 29 November 2021

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Magnon transport in Y3Fe5O12/Pt nanostructures with reduced effective magnetization

J. Gückelhorn, T. Wimmer, M. Müller, S. Geprägs, H. Huebl, R. Gross, and M. Althammer

Phys. Rev. B 104, L180410 – Published 29 November 2021

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Magnon transport in $Y_{3} {Fe}_{5} O_{12} / Pt$ nanostructures with reduced effective magnetization