Spin current studies in Fe/Ag,Au/Fe by ferromagnetic resonance and time-resolved magneto-optics

A precessing magnetization within a magnetic double layer acts as a peristaltic spin pump which transports spin momentum but no net electric charge. Crystalline Fe single layers Au/12Fe/GaAs(001) and double layers Fe12/(Au,Ag)/Fe16/GaAs(001) were prepared by molecular beam epitaxy, where the integers represent the number of Fe atomic layers, and (Au,Ag) represents a set of gold and silver layers of different thicknesses. Ferromagnetic resonance (FMR) was used to investigate spin diffusion in thick Au layers in Au/12Fe/GaAs(001) samples. Time-resolved magneto-optical Kerr effect (TRMOKE) measurements are an ideal tool for investigating the propagation of spin currents in these structures. Spin currents generated by the bottom 16Fe layer propagated across the normal metal spacer and resulted in rf excitations in the top 12Fe film. Landau-Lifshitz-Gilbert equations of motion modified by spin pump and spin sink effects were used to interpret the FMR and TRMOKE measurements. The spin diffusion lengths in Au were Ag were found 34 and 170 nm, respectively. (c) 2008 American Institute of Physics.