Current-Induced High Frequency Excitations in Py-based Nanopillars

To study how high frequency excitations induced by high current densities in ferromagnetic/non-magnetic/ferromagnetic (F/N/F) nanopillars vary with applied magnetic field H and current I, we have assembled a system containing 40 GHz picoprobes, a 12 GHz spectrum analyzer, and a 40 GHz Microwave-generator-based system that can be used as a spectrum analyzer up to 40 GHz. Our first measurements, on Permalloy (Py = Ni(84)Fe(16))-based nanopillars of the form Cu(80nm)/Py(30nm)/Cu(10nm)/Py(6nm)/Cu(5nm)/Au(200nm), yielded peaks at frequencies in the range 1 to 2 GHz. We will describe how the frequencies and heights of these peaks vary with H and I.