Cryogenic Magnetization Dynamics in Chemically Stabilized, Tensile-Strained Ultrathin Yttrium Iron Garnets with Tunable Magnetic Anisotropy

We report an interfacial chemical stability-driven reduction of low-temperature damping losses in tensile-strained, ultrathin Y₃Fe₅O₁₂ (YIG) films grown by pulsed laser deposition, exhibiting ultralow room-temperature damping constants and tunable magnetic anisotropy. Comparative broadband FMR measurements show that tensile-strained YIG films on Gd₃Sc₂Ga₃O₁₂ (GSGG) retain measurable damping even at nanometer thicknesses and cryogenic temperatures down to 2 K, outperforming relaxed films on Gd₃Ga₅O₁₂. Based on static magnetometry measurements along with microstructural and compositional analyses, we attribute these enhanced dynamic properties to the suppression of interdiffusion across the YIG/GSGG interface, resulting from enhanced chemical stability and favorable growth kinetics by the presence of Sc. Our findings highlight the importance of chemical and kinetic factors in achieving a few-nanometer-thick YIG film with negligible low-temperature damping dissipation and perpendicular magnetic anisotropy for cryogenic spintronic applications.