Tuning the Damping of Spin Wave Modes by Spin Hall Current in Permalloy/Platinum Wires

A spin current in solids is the flow of electron spin angular momentum without electric charge flow in the same direction. Since its theoretical prediction, tremendous efforts were put into realizing it in bulk materials and heterostructures. The spin can apply a spin transfer torque to magnetization of a magnetic material without any charge current flowing through this material and thus can be used for manipulation of magnetization of both magnetic conductors and insulators. The recent discovery of spin Hall effect (SHE) has drawn significant attention because it not only provides simple method for generation of pure spin currents in spin-orbit materials.;In this dissertation, measurements of the spectral properties of bulk and edge spin wave modes in Permalloy/ Platinum (Py/Pt) bilayer wires in the presence of high current densities are reported. The charge current in the Pt layer (spin-orbit material) induces a pure spin current via SHE that flows from Pt into Py, applies a spin torque, and tunes its magnetization dynamics. We find that the damping parameters of all spin wave modes in the Py wire can be reduced by the spin torque arising from the spin Hall current in Pt. However, the damping reduction is strongest for the quasi-uniform mode and weakest for the edge mode. Our work demonstrates that the spin Hall torque does not uniformly affect all spin wave modes and reveals the importance of extrinsic contributions to the spin wave damping for manipulation of the magnetization by spin Hall current.