Measurements Of Spin Torques Generated By Topological Insulators And Heavy Metals

Abstract

This dissertation discusses measurements of spin torques generated by two classes of materials; heavy metals and topological insulators. In the first half, we use spin torque ferromagnetic resonance with and without the addition of DC currents to measure spin torques generated by the topological insulator bismuth selenide, and find that the effective spin torque ratio, a figure of merit for generating spin torques, is at least of order ~ 1, larger than any other material measurement at room temperature to date. In the second half, we discuss a recently-developed method of measuring spin torques optically using the magneto-optic Kerr effect, and the construction of such an experimental setup at Cornell. This new technique may allow easy measurements of spin torques in systems with insulating ferromagnetic layers, which is not possible with spin torque ferromagnetic resonance. We compare it to spin torque ferromagnetic resonance and other electrical measurements using measurements of platinum / permalloy and bismuth selenide / permalloy bilayers, and find that it is agrees well with other methods.