Z-shaped waveguides using complete band gaps in magnonic crystals of yttrium iron garnet and a copper hole array

Guiding spin wave (SW) signals around turns in integrated magnonic circuits remains a challenge. Here, we calculated efficient SW transmission through Z-shaped turns of 120° using low-loss magnonic crystal (MC) waveguides comprising yttrium iron garnet (YIG) and a Cu hole array. The MCs were optimized using a finite integration technique, showing a complete magnonic band gap with a width of 15.1 MHz at a center frequency of 1.811 GHz. The MC waveguide showed 5.7 × 10^3 times stronger SW propagation than ridge-type waveguides by avoiding SW depression caused by inhomogeneous internal magnetic field distributions in the YIG film. The effect of the bending radius on the SW propagation was evaluated through simulations. The proposed MC waveguide plays a vital role in SW waveguide integration by maintaining homogeneous magnetic field distributions throughout the unprocessed YIG film.