films into heavy metals

Low-damping magnetic insulators are essential to the growing field of spintronics since they can generate and transfer spin currents without associated charge currents. We have recently developed a new ferrimagnetic insulator, MgAl_0.5Fe_1.5O₄ (MAFO), which has Gilbert damping as low as 1x10^-3. Through resonant excitation of the MAFO layer, we observed significant spin pumping from MAFO films into adjacent Pt and β-W layers by enhanced Gilbert damping and electrical voltage peaks that appear at ferromagnetic resonance (FMR). There is a reversal of the transverse voltage signal in MAFO/Pt and MAFO/β-W, which is consistent with the opposite signs of the spin Hall angle in these two materials and indicates the signal is due to the inverse spin Hall effect and not to proximity-induced anisotropic magnetoresistance (AMR). Further, angular dependent magnetoresistance (ADMR) measurements reveal that the spin Hall magnetoresistance (SHMR) is 7-10 times larger than the AMR contribution, so spin pumping effects dominate the magnetic dynamics of the bilayers. From FMR and ADMR measurements, we deduced a spin-mixing conductance of ~3x10¹⁴ Ω^-1 m^-2 in MAFO/Pt. Together, these measurements indicate that MAFO is an excellent candidate for efficient spin current-based heterostructures and devices.