Magnon-Mediated Spin Transport in TmIG/Au/TmIG Valves with Perpendicular Magnetic Anisotropy*

Rare-earth iron garnet films with perpendicular magnetic anisotropy (PMA) have been extensively explored in magnon spintronics where spin currents carried by magnons could be used to carry, transport, and process information leading to devices free of Joule heating. In this work, we investigate the spin dynamics and the transport of thermally driven spin currents in valves composed of two layers of TmIG (Tm₃Fe₅O₁₂) thin films with PMA separated by Au. We employed the ferromagnetic resonance technique to probe the magnetic anisotropies and the spin Seebeck effect (SSE) to excite magnon-mediated spin currents. The spin currents were detected through the inverse spin Hall effect as a micro-voltage (V_SSE) at the edges of a platinum electrode deposited on the top of TmIG(30 nm)/Au(8 nm, 12 nm, 16 nm)/TmIG(15 nm). The results show the V_SSE depends on the relative orientation of the TmIG layers assuming its maximum value when the magnetizations are parallel and minimum when antiparallel. These structures could be used to control the transmission coefficient of spin waves in wave-based computing devices.