All-Angle Collimation for Spin Waves

Collimation of monochromatic beams of spin waves results from refraction at the interface between two magnetic half-planes. Collimation occurs for a broad range of the angles of incidence for homogenous Co and Permalloy (Py) half-planes due to the intrinsic anisotropy of spin-wave propagation in these materials. The effect arises in samples saturated by an in-plane magnetic field tangential to the interface. Further, collimation for all possible angles of incidence occurs in a system where the incident spin wave is refracted at the interface between homogeneous and periodically patterned layers of yttrium-iron garnet (YIG). The refraction was investigated by the analysis of isofrequency dispersion contours for both pairs of materials (Co/Py and uniform YIG/patterned YIG), which are calculated by the plane-wave method. In addition, refraction in the Co/Py system was studied with micromagnetic simulations.