Magnetization dynamics in synthetic antiferromagnets: Role of dynamical energy and mutual spin pumping

We investigate magnetization dynamics in asymmetric interlayer exchange coupled Py/Ru/Py trilayers using both vector network analyzer-based and electrically detected ferromagnetic resonance techniques. Two different ferromagnetic resonance modes, in-phase and out-of-phase, are observed across all three regimes of the static magnetization configurations, through antiparallel alignment at low fields, the spin-flop transition at intermediate fields, and parallel alignment at high fields. The nonmonotonic behavior of the modes as a function of the external field is explained in detail by analyzing the interlayer exchange and Zeeman energies and is found to be solely governed by the interplay of their dynamical components. In addition, the linewidths of both modes were determined across the three regimes and the different behaviors of the linewidths versus external magnetic field are attributed to mutual spin pumping induced in the samples. Interestingly, the difference between the linewidths of the out-of-phase and in-phase modes decreases at the spin-flop transition and is reversed between the antiparallel and parallel aligned magnetization states.