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

Abstract

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 (4πMS) and coercivity (HC), 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 4πMS value of 1775, closely resembling the bulk YIG value, with an exceptionally low coercivity (HC < 5 Oe). From ferromagnetic resonance (FMR) measurements, the estimated effective saturation magnetization (4πMeff) is found to be very much different from the 4πMS obtained from PPMS and is attributed to the presence of stressed-induced magnetic anisotropy (HK) in YIG films. The FMR linewidth (ΔH) of the YIG films is found to be quite sensitive to HK and the minimum ΔH value of 80 Oe is observed in the film with the lowest HK. 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. © 2024, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.