Domain-wall resonance in exchange-coupled magnetic films

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Abstract
Exchange coupling between magnetic films in multilayer geometries can strongly influence magnetization behavior and spin-wave energies by correlating the motion of spins in one film with the motion of spins in adjacent films. In a similar fashion correlations can be expected between domain walls existing in neighboring exchange coupled films. In this paper we show that the motion of domain walls in neighboring films can depend strongly on interfilm exchange coupling. A static equilibrium configuration exists for the domain walls, and small amplitude oscillations about equilibrium can result in domain-wall resonances that involve interfilm exchange energies. Frequencies for optic- and acoustic-type domain-wall resonances are calculated and effects of a small static applied magnetic field are examined, revealing distinctly different behaviors for the acoustic and optic domain-wall resonances. The possibility for sensitive measurements of the local coupling by studying domain-wall resonance is discussed. Resonances with parallel and antiparallel coupling are considered and the response to a small in-plane driving field is calculated.