Damping Enhancement in YIG at Millikelvin Temperatures due to GGG Substrate

Abstract

Quantum magnonics aims to exploit the quantum mechanical properties of magnons for nanoscale quantum information technologies. Ferrimagnetic yttrium iron garnet (YIG), which offers the longest magnon lifetimes, is a key material typically grown on gadolinium gallium garnet (GGG) substrates for structural compatibility. However, the increased magnetic damping in YIG/GGG systems below 50K poses a challenge for quantum applications. Here, we study the damping in a 97nm-thick YIG film on a 500$\mu$m-thick GGG substrate at temperatures down to 30mK using ferromagnetic resonance (FMR) spectroscopy. We show that the dominant physical mechanism for the observed tenfold increase in FMR linewidth at millikelvin temperatures is the non-uniform bias magnetic field generated by the partially magnetized paramagnetic GGG substrate. Numerical simulations and analytical theory show that the GGG-driven linewidth enhancement can reach up to 6.7 times. In addition, at low temperatures and frequencies above 18GHz, the FMR linewidth deviates from the viscous Gilbert-damping model. These results allow the partial elimination of the damping mechanisms attributed to GGG, which is necessary for the advancement of solid-state quantum technologies.

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Cited by in corpus (5)

• Elimination of substrate-induced FMR linewidth broadening in the epitaxial system YIG-GGG by microstructuring
• YSGAG: The Ideal Substrate for YIG in Quantum Magnonics
• Cryogenic Magnetization Dynamics in Chemically Stabilized, Tensile-Strained Ultrathin Yttrium Iron Garnets with Tunable Magnetic Anisotropy
• Unified theory of magnetization temperature dependence in ferrimagnets
• Strain-Induced Enhancement of Spin Pumping in Pt/YIG Bilayers