Nonreciprocal spin wave spectroscopy of thin Ni-Fe stripes

The authors report on the observation of nonreciprocal spin wave propagation in a thin (similar to 200 nm) patterned Ni-Fe stripe. The spin wave transmission spectrum is measured using a pair of microstrip lines as antennas. The nonreciprocity of surface wave dispersion brought about by an adjacent aluminum ground leads to a nonreciprocal coupling of the antennas. The effects of Ni-Fe film conductivity, thickness, and reflections caused by the lateral confinement of the magnetic stripe are discussed. The nonreciprocity observed in this structure can potentially be used to realize nonreciprocal microwave devices on silicon.