Effect of distance between a magnet layer and an excitation antenna on the nonreciprocity of magnetostatic surface waves

We investigated the effect of the distance between a magnetic layer and an excitation antenna on the nonreciprocity of magnetostatic surface waves (MSSWs), using devices with various thicknesses of the SiO2 layer (t SiO2) to isolate an antenna from a permalloy layer. The nonreciprocity of MSSWs increases with increasing t SiO2. This increase in MSSW nonreciprocity is caused by an increase in the ratio of the MSSW excitation efficiency of the out-of-plane component of a microwave field to that of the in-plane component of a microwave field. Thus, we found that the nonreciprocity of MSSWs can be controlled by a very simple method.