Enhanced optical mode coherence in exchange coupled soft magnetic multilayers.

We report on an all-optical investigation of coupled spin excitation modes in a series of magnetic trilayer structures. Using time-resolved magneto-optic Kerr effect (tr-MOKE) magnetometry, we observe multi-mode coherent spin excitations in Ni 81 Fe 19 /Ru/ Co 49 Fe 49 V 2 multilayers even though the tr-MOKE optical detection is sensitive only to the Co 49 Fe 49 V 2 magnetization dynamics. Frequency shifts of the different modes indicate that the coupling between the Ni 81 Fe 19 and Co 49 Fe 49 V 2 layers varies from anti-ferromagnetic to ferromagnetic to uncoupled as the Ru spacer layer thickness is increased from 8 Å to 200 Å. The lifetime of the high frequency coherent oscillations in the Co 49 Fe 49 V 2 layer increases by over 200%–300% even in the case of uncoupled Ni 81 Fe 19 and Co 49 Fe 49 V 2 layers with a 200 Å thick Ru spacer. The results suggest an additional method to decrease the damping of high-moment alloys in layered magnetic nanostructures. [ABSTRACT FROM AUTHOR]