Annealing and Thickness-Dependent Structural, Magneto-Optical, and Ferromagnetic Resonance Properties of RF-Sputtered YIG/GGG Thin Films

Yttrium iron garnet (Y3Fe5O12, YIG) films were deposited on gadolinium gallium garnet (Gd3Ga5O12, GGG) through room-temperature RF magnetron sputtering and annealed in flowing oxygen. We examined the effects of annealing temperature and film thickness using X-ray diffraction (XRD), scanning electron microscopy (SEM), longitudinal magneto-optical Kerr effect (MOKE) loops and multi-frequency field-swept ferromagnetic resonance (FMR). Representative SEM images showed laterally uniform surface backgrounds with sparse localized particulates. Gaussian switching-field fits with residual-bootstrap analysis were used to obtain Kerr-derived coercive fields, switching-field standard deviations and their normalized ratios. In the temperature series, the 900 °C sample gave the smallest fitted σSFD/Hc, whereas the 850 °C sample gave the lowest effective damping of α = (4.2 ± 0.27) × 10−3. In the thickness series annealed at 850 °C, the 75 nm film combined the smallest σSFD/Hc (3.11 ± 0.38%) with the lowest measured α, (5.84 ± 0.16) × 10−3. The different temperature optima show that switching uniformity and dynamic loss should be assessed separately. The results provide an empirical comparison for selecting processing conditions within the investigated RF-sputtered YIG/GGG series.