Control of spin wave Doppler shift by movable magnetic dipole field

Efficient manipulation of spin waves (SWs) is crucial for the development of advanced sensing applications in magnonics. One of the critical dynamic effects in spin wave propagation is the Doppler shift, which reflects the interaction between moving boundaries or varying magnetic environments and the propagating magnons. In this study, we propose a feasible approach to actively modulate the spin wave Doppler shift by utilizing an effective magnetic dipole field generated by a movable magnet. This movable magnet introduces a dynamic boundary and a spatially varying magnetic field between two magnetic regions, offering a controllable platform for spin wave modulation. Through micromagnetic simulations, we demonstrate that the Doppler-shifted frequencies of reflected spin waves are invariant with respect to the dipole field strength. In contrast, the transmitted spin waves exhibit a pronounced frequency shift that scales with the dipole field, highlighting the potential for field-tunable magnonic devices. These findings provide a new strategy for dynamic control of spin wave propagation, with promising implications for the development of tunable spintronic sensors.