Effect of buffer layer Bi₂Te₃ on anisotropic Gilbert damping of Fe/α-GeTe on Al₂O₃ substrate

The α-GeTe is a typical ferroelectric Rashba semiconductor (FERSC) that has attracted a lot of attention in spintronics. The Fe/α-GeTe grown on Si substrates has anisotropic Gilbert damping. However, the effect of Al₂O₃, as another common substrate, remains unknown when α-GeTe is grown on it. Here, we fabricated α-GeTe thin films using Al₂O₃ substrates. The α-GeTe directly grown on Al₂O₃ exhibits an in-plane polycrystalline structure. A Bi₂Te₃ buffer layer can make the α-GeTe exhibit a single-crystal feature. The anisotropic Gilbert damping of FM layers is present in Fe/α-GeTe/Bi₂Te₃/Al₂O₃ and vanished in Fe/α-GeTe/Al₂O₃. Our finding illustrates that α-GeTe growth on Al₂O₃ with a Bi₂Te₃ buffer layer can serve as a suitable platform for anisotropic research. Our work paves the way for the application of the Al₂O₃-based α-GeTe thin films in anisotropic electronics.