Abstract Using micromagnetic simulations and analytical theory, we study temporal magnetic interfaces in ultrathin CoFeB films with perpendicular magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interaction. We show that time refraction and reflection are governed by precession ellipticity, acting as a magnonic temporal impedance, while smooth field ramps suppress temporal reflections. Near the transition from a uniform state to stripe domains, the exceptional point and critical fields delimit damping, slow-instability, and strong-instability regimes. In the slow-instability window, Gilbert damping counterintuitively drives spin-wave growth with a rate proportional to the damping parameter. Micromagnetic simulations confirm that a temporal-slab protocol exploiting this regime achieves up to 175-fold frequency-preserving amplitude amplification without continuous power injection. Energy analysis indicates that the field ramp stores energy in the metastable uniform state below the stripe-domain transition, later released into growing spin-wave excitations, consistent with the antimagnonic framework. These results establish temporal field modulation as a route to reconfigurable spin-wave gain.
Sobucki et al. (Mon,) studied this question.