Frequency and Field Angle Dependent Spin Wave Intensities in a Magnetic Y-Structure

Spin-based logic devices that use spin waves or magnons to transmit and process information offer potential advantages over conventional devices for logic operations. Here we investigate the effect of driving frequency and magnetic field angle on spin wave propagation through a Y-shaped junction. Micro-focus Brillouin light scattering (micro-BLS) measurements were made to obtain spatial maps of spin wave intensities in a 40-nm thick Ni₈₀ Fe₂₀ (Permalloy) Y-shaped structure made of microstrips with widths of w = 2.4-μm. A 10-μm wide gold microstrip antenna was used to excite spin waves in the two arms that form the top of the Y-structure, and then the spin waves converge in the base of the Y. Spin wave propagation patterns obtained with the magnetic field applied in-plane and perpendicular to the direction of spin wave propagation in the base of the Y, a configuration known as the surface wave Damon Esbach (DE) configuration, show similar spin wave intensities in the two arms and a symmetric pattern in the base. The relative intensities of the spin waves in the two arms and interference pattern in the base differ when the field angle is tilted in plane. Changes in the driving frequency produce similar effects. These changes in the spin wave propagation patterns can be understood by examining the spin wave dispersion relations for microstrips.