Exploring magnon-induced spin transfer torques with ultrafast MOKE*

We report our efforts to use pump-probe time-resolved magneto-optical Kerr effect (MOKE) to investigate magnon-induced spin torque. A femtosecond laser pulse is used to create magnons that transfer their momentum to the free layer; a probe pulse subsequently probes the spin torque transfer through the device. The samples had the structure Ta (5nm)/ Ni\textunderscore 80Fe\textunderscore 20 (10nm)/ Cu (5nm)/ Ni\textunderscore 80Fe\textunderscore 20 (10nm)/ IrMn (15nm)/ Ta (5nm), and were grown on Si (100) substrates via magnetron sputtering. Using e-beam lithography, nanopillars with dimensions 200 nm by 140 nm were created in an array, which was probed by ultrafast MOKE.