Abstract Control of spin‐wave (SW) propagation is demonstrated by introducing a micro‐air gap into a nanometer‐thick yttrium iron garnet (Y 3 Fe 5 O 12 , YIG) microstructure. SWs traverse the gap with reduced intensity following an exponential–linear decay with air gap length, attributed to coupling between incident and reflected dipolar SWs via a time‐varying stray magnetic field. By tuning gap length, SW intensity is balanced to address nonreciprocity in counterpropagating magnetostatic surface SWs within an inl…