Spin transport and standing spin waves generation in heavy metal-magnetic insulator-ferromagnet hybrid structures

Magnons (or spin waves) are collective excitations of electrons’ spin angular momenta in magnetic or antiferromagnetic materials. The excitation and tunability of magnons in low-damping magnetic insulators, e.g., the yttrium iron garnet (YIG), is particularly interesting because it could offer much longer magnon propagation length and potential broad spintronics applications.
Here, we study a platinum/YIG/permalloy hybrid structure, where YIG is the magnetic spacer and permalloy (Py) is a low-damping ferromagnetic metal. Through external microwave excitation, the YIG layer and the Py layer can be excited to reach the ferromagnetic resonance modes individually, and we have detected the spin current signal from the Py spin pumping process transmitted through the YIG layer and converted to voltage signals in the platinum (Pt) layer by the inverse spin Hall effect. More importantly, we have detected additional resonance peak and spin pumping voltage signals which are corresponding to the perpendicular standing spin waves (PSSW) in the YIG layer. At specific frequency, this PSSW in YIG could be coupled with the magnon mode in Py, which could possibly facilitate the magnon spin transport from the Py layer to the bottom Pt layer.