Reconfigurable control of coherence, dissipation, and nonreciprocity in cavity magnonics.

Precise control of coupling strength, damping rate and nonreciprocity in photon-magnon systems is essential for advancing hybrid quantum technologies, including reconfigurable microwave components and quantum transducers. Here, we demonstrate magnetic field angle-dependent control of photon-magnon coupling and magnon dissipation in a cross-shaped microwave cavity supporting a spatially nonuniform radio-frequency (rf) magnetic field. By rotating the external magnetic field angle θ relative to the normal of the transmission line within the cavity plane, we simultaneously control the coherent coupling strength [Formula: see text], the ferromagnetic resonance (FMR) damping rate, and the system's nonreciprocal response. The nonuniform rf field selectively excites both the uniform FMR mode and finite-wavevector spin waves in an Yttrium Iron Garnet (YIG) film, enabling angle-dependent two-magnon scattering. While typically regarded as a passive loss mechanism, we show that two-magnon scattering can serve as a dynamic and reversible knob to control magnon damping. Moreover, we realise nonreciprocity originating from the spatial asymmetry of the rf field, in addition to conventional phase-based schemes. These findings introduce new opportunities for in situ control of coherence, dissipation, and nonreciprocity in cavity magnonics, with broad implications for reconfigurable quantum and spintronic systems.