Micromagnetic Modelling of the Dynamics of Exchange Springs in Multi-Layer Systems

Exchange springs are formed in multilayers of alternating hard and soft ferromagnetic materials which are exchange coupled at their interfaces. These systems are rich of interesting physical properties, which can be tuned by selecting suitable geometries and compositions. In this paper, we present a computational study of the dynamics of a tri-layer DyFe₂/YFe₂/DyFe₂ exchange spring system near the bending field (the field required to twist the magnetization of the soft YFe₂ layer out of the aligned state). The dynamical reaction of the system to small variations of the applied field is studied and its oscillatory nature is analyzed numerically. The behaviors of the decay times, the frequencies, and amplitudes reveal enhanced responses of the system near the bending field