Tuning ferromagnetic resonance via disorder/order interfaces

Abstract

Ferromagnetic resonance of a thin film alloy has been tuned by inducing lateral interfaces between layers differing in their lattice ordering and magnetic properties. By disordering B2 Fe60Al40 thin films to the A2 structure, thereby manifesting planar A2/B2 interfaces at selected depths, we show that the resonance lines at 10 GHz are shifted by 284 mT and 35 mT for fields applied perpendicular-to-plane and in-plane, respectively. The resonance line shift occurs over a broad frequency range and is driven by strain relaxation due to the increasing magnetic layer thickness. A finer anomalous line shift occurs as the A2/B2 interface approaches the film/substrate interface prior to being expelled from the film. The A2 structure can be reannealed to the B2 order, implying that disorder/order interface modification can provide a path for reversibly encoding resonant properties in alloy thin films.