Resonant phonon-induced magnetic domain dynamics as Néel temperature is approached in nickel oxide

Abstract We investigated the temperature dependence and mode sensitivity of antiferromagnetic (AFM) domain dynamics in nickel oxide (NiO) by time-resolved imaging of phonon-mediated changes over the temperature range from ∼300 K to ∼523 K. Resonant second-order transverse optical (2TO) and longitudinal optical (LO) phonon excitations were conducted using a mid-infrared free-electron laser. The AFM domain images were recorded using magneto-optical linear birefringence microscopy. Our experiments revealed distinct domain reconfigurations: resonant 2TO phonon excitation induced domain changes that persisted on the millisecond timescale (1.05 ± 0.03 ms) with thermally retarded recovery, whereas LO phonon excitation produced rapid microsecond recovery (80.3 ± 25.4 μs), accelerating with increasing temperature. These contrasting responses reflect mode-specific spin-phonon coupling conditions in NiO, indicating that temperature-dependent domain reconfiguration is governed by slower energy redistribution processes that extend beyond solely phonon relaxations.