Brillouin Light Scattering Study of Linear and Nonlinear Spin Dynamics in Magnetic Thin Films

Brillouin light scattering (BLS), an inelastic light scattering technique, has been used for decades to study phonons and magnons, also known as spin waves, in a wide range of materials. The BLS technique has proven to be a useful tool to investigate spin wave dynamics in continuous thin films and it has also been used to explore driven spin wave processes in low-damping yttrium iron garnet (YIG) films where the spin waves propagate for distances over several millimeters. In both cases, spatial resolutions of a few tens of micrometers are sufficient to resolve the dynamics. Within the past few years, advancements in the BLS technique have included the development of micro-BLS and with this new technique spatial mapping of spin dynamics on sub-micrometer length scales can now be realized. This talk will cover BLS measurements of thermally excited magnons in Fe65Co35 and parametrically excited magnons in YIG. A set of continuous Fe65Co35 thin films, a high-magnetization alloy that is used in magnetic read/write heads, were studied to determine the exchange constant for this material and time and space resolved-BLS measurements were conducted on YIG to determine the group velocities of magnons formed by nonlinear three magnon splitting and confluence processes. The development of micro-BLS and the measurements of confined spins waves in patterned Permalloy nanostructures will also be discussed.