Direct current control of three magnon scattering processes in spin-valve nanocontacts

摘要

We have investigated the generation of spin waves in the free layer of anextended spin-valve structure with a nano-scaled point contact driven by bothmicrowave and direct electric current using Brillouin light scatteringmicroscopy. Simultaneously with the directly excited spin waves, strongnonlinear effects are observed, namely the generation of eigenmodes withinteger multiple frequencies (2 \emph{f}, 3 \emph{f}, 4 \emph{f}) and modeswith non-integer factors (0.5 \emph{f}, 1.5 \emph{f}) with respect to theexcitation frequency \emph{f}. The origin of these nonlinear modes is tracedback to three magnon scattering processes. The direct current influence on thegeneration of the fundamental mode at frequency \emph{f} can be related to thespin-transfer torque, while the efficiency of three-magnon-scattering processesis controlled by the Oersted field as an additional effect of the directcurrent.