Evidence of spin-pumping effect in the ferromagnetic resonance of coupled trilayers

The spin dynamics between two ultrathin ferromagnetic layers exchange coupled via a nonmagnetic spacer is studied using in situ ferromagnetic resonance. The angular and the temperature dependence of the linewidth, especially the pronounced changes of the former, can be understood assuming the presence of an additional Gilbert damping resulting from the spin-current pumped through the interface between the ferromagnetic and nonmagnetic material or by considering the dynamic part of the interlayer exchange coupling. The competition between the Gilbert damping inherent in the ferromagnetic film and the Gilbert damping developed by the interface leads to an irregular behavior of the temperature dependence of the resonance linewidth for both the in-phase and out-of-phase precessing modes. It is shown that the oscillatory nature of the coupling is also revealed in the dependence of the resonance linewidth DeltaH on the spacer thickness.