Probing magnons in metallic magnetic bilayers for spintronic applications

The field of spintronics, which concerns itself with the manipulation of the spin degree of freedom for information storage and processing purposes, has made enormous progress in the last decades going from a theory to commercial products. The field is continuously driven by the demand of storing information with high density and reduced energy consumption. Progress often occurs by exploring material combinations and new device geometries. In recent years, magnetic bilayers consisting of a ferromagnet and a heavy metal thin films have emerged as a promising material platform for new generations of spintronic devices. Many interesting fundamental questions remain to be addressed in these seemingly simple bilayers. This thesis focuses on studying different bilayers in order to realize new spin torque oscillators and to search for optimal materials for information storage in novel spin textures such as skyrmions. The materials and devices described below are characterized using Brillouin Light Scattering (BLS). Spin torque oscillators show enormous promise as components in spintronic circuits due to their high energy efficiency and tunable frequencies. Additionally their nonlinear properties make them promising candidates for neuromorphic computing applications. We study nanowire spin torque oscillators using both insulating(YIG) and metallic(Ni20Fe80) magnetic layers on top of a Heavy Metal layer (Pt). For the insulating case, we show the feasibility of making devices with the insulating layer as well as the impact of the Spin Seebeck effect in increasing energy efficiency. For the metallic wires, we study new phenomena that emerge from extending the dimensionality of the STOs to one dimension. In particular, we show the existence of two distinct modes whose different properties might be exploitable for more exotic microwave sources. We study these wires with a micrometer focus BLS setup to ensure the spatial resolution needed to gain information from the nanowires. We also explore the possibility of chiral spintronics by studying bilayers showing significant interfacial Dzyaloshinskii-Moriya Interaction (DMI) while also possessing other characteristics which may be useful for spintronics. First we study Pd25Pt75 which combines high spin Hall efficiency as well as a strong tunable DMI when combined with a Co based magnetic layer. Second we study epitaxially grown Co25Fe75 which combines a strong DMI with a record low magnetic damping for a metallic film. The results of these sections provide guidance for future device engineering by suggesting promising materials. We study these systems with a BLS setup which uses a large spot size to maintain momentum resolution. We measure the asymmetric shift between the Stokes and anti-Stokes peak. This shift changes linearly with respect to wavevectors, allowing one to extract interfacial DMI.