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Updated: Aug 21, 2026

Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals
Published on: August 15, 2018
Tunable magnon polaritons via Eddy-current-induced dissipation in metallic-banded YIG spheres
Tatsushi Uno1, Shugo Yoshii2, Sotaro Mae1
1Department of Electronic Science and Engineering, Kyoto University, Kyoto, 615-8510, Japan.
Abstract:
We demonstrate a robust method to dynamically tune magnon dissipation in yttrium iron garnet spheres by equipping a metallic band around the sphere's equator, enabling precise control over magnon-photon coupling states. The collective magnetization dynamics in the YIG sphere induce circular eddy currents in the metallic band, whose magnitude can be systematically varied by adjusting the angle between the metallic band plane and an external static magnetic field. This angular dependence yields a pronounced modulation of the ferromagnetic resonance (FMR) linewidth, facilitating seamless transitions between the Purcell and strong coupling regimes without altering photon resonator parameters. Systematic FMR and resonator spectroscopy measurements confirm that eddy-current-induced losses govern the primary mechanism behind the observed tunable damping. By achieving extensive cos2θ-type tunability of magnon relaxation rate, we precisely control the magnon-photon coupling state, approaching the critical coupling condition (g = γ/2). These results establish the YIG-metallic-band platform as a versatile and practical approach for engineering tunable magnon-polariton systems and advancing magnonic applications, including those exploring non-Hermitian magnonics.
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