Strain-Tunable Magnetic Anisotropy in Sputtered Thulium Iron Garnet (TIG) Thin Films and TIG/Au/TIG Trilayers*

Ferromagnetic insulator thin films have been explored for developing spintronic devices. When combined with quantum materials, the strongly correlated interaction from the proximitized interface results in intense local magnetic fields which modulates them to displaying new interface physical phenomena. We investigate ways to tune the magnetic anisotropy in TIG films by selecting their thickness, substrate, and annealing conditions. When deposited over (111) GGG, they present a negative magnetostriction constant which favors a perpendicular magnetic anisotropy (PMA). While PMA allows high magnetic storage density in hard disk drives, it is required for breaking the time-reversal symmetry in topological insulators (TIs) to aim towards quantized anomalous Hall state in TIs. Controlling the film preparation parameters we observed that TIG films under compressive strain display an in-plane magnetic anisotropy, whereas films under tensile strain demonstrated PMA. These results led to the successful fabrication of TIG/Au/TIG magnon valve structures with independent magnetic switching of each TIG layer.