Sputter-deposited YIG thin films with perpendicular magnetization enabling spin wave propagation and spin-orbit torque switching

Yttrium iron garnet (YIG) has been widely recognized as an ideal medium for magnon-based information transport due to its extremely low magnetic damping. However, growth of YIG with perpendicular magnetization has been typically limited, restricting its integration with spintronics and magnonic devices. In this study, we demonstrate sputter-deposited YIG thin films exhibiting perpendicular magnetic anisotropy (PMA) and low damping constant, enabling both spin-wave propagation and spin-orbit torque (SOT)-induced magnetization switching.

The 20-nm-thick YIG layers were grown on SGGG (111) substrate using magnetron sputtering, followed by post-annealing to crystallize the YIG thin film. X-ray diffraction measurements revealed in-plane tensile strain compared to bulk YIG, suggesting that the resulting lattice distortion is responsible for the emergence of PMA. Under optimized fabrication conditions, a damping constant below 1 × 10^-3 was confirmed by ferromagnetic resonance measurements. Spin wave transport was investigated by using the vector network analyzer and two separated coplanar waveguides, showing spin wave propagation with over several micrometers with a group velocity of 0.2 km/s. In heterostructure with a heavy metal layer of Pt(6 nm), current-induced SOT successfully switched the perpendicular magnetization.