Evolution of microstructure, magnetic and microwave properties of sputter deposited polycrystalline YIG thin films

Yttrium iron garnet (YIG: Y₃Fe₅O₁₂) is an ideal magnetic material with potential applications in microwave and spintronic devices. A key prerequisite for seamless integration into current semiconductor electronics is the growth of high-quality YIG films on substrates beyond isostructural Gadolinium gallium garnet. In this context, we present the successful fabrication of YIG thin films with varying thickness (70 ≤ t ≤ 380) on fused quartz substrates utilizing radio-frequency (rf) magnetron sputtering. The Rietveld refinement of the X-ray diffraction data uncovers the formation of body-centered cubic single-phase polycrystalline YIG with the space group of Ia-3d. Saturation magnetization (4πM_S) and coercivity (H_C), as determined by the physical property measurement system (PPMS), exhibit a dependence on the film’s thickness (t). Remarkably, the film with t = 380 nm shows a 4πM_S value of 1775, closely resembling the bulk YIG value, with an exceptionally low coercivity (H_C < 5 Oe). From ferromagnetic resonance (FMR) measurements, the estimated effective saturation magnetization (4πM_eff) is found to be very much different from the 4πM_S obtained from PPMS and is attributed to the presence of stressed-induced magnetic anisotropy (H_K) in YIG films. The FMR linewidth (ΔH) of the YIG films is found to be quite sensitive to H_K and the minimum ΔH value of 80 Oe is observed in the film with the lowest H_K. The findings indicate that YIG films deposited on quartz substrates have potential advantages for their application in semiconductor-integrated devices. Importantly, this study delves into the fundamental intricacies of YIG growth on non-garnet substrates and offers a well-optimized recipe for generating high-quality YIG thin films through RF sputtering.