  To realize spin wave logic gates programmable phase inverters are essential.
We image with phase-resolved Brillouin light scattering microscopy propagating
spin waves in a one-dimensional magnonic crystal consisting of dipolarly
coupled magnetic nanostripes. We demonstrate phase shifts upon a single
nanostripe of opposed magnetization. Using micromagnetic simulations we model
our experimental finding in a wide parameter space of bias fields and wave
vectors. We find that low-loss phase inversion is achieved, when the internal
field of the oppositely magnetized nanostripe is tuned such that the latter
supports a resonant standing spin wave mode with odd quantization number at the
given frequency. Our results are key for the realization of phase inverters
with optimized signal transmission.
