Effect of Lower Demagnetizing Field on Switching Currents of Magnetic Nanopillars

\textbf{Katine et al.[1] derive an expression of the form Is $\propto $ [Heff+2$\pi $M] (where 2$\pi $ times the magnetization M comes from the demagnetizing field for the switching layer) for the switching current in a ferromagnetic/non-magnetic/ferromagnetic (F/N/F) nanopillar. If this equation correctly describes Is, then reducing the demagnetizing field should apparently reduce Is. The interfacial interaction between Co and Au favors a perpendicular orientation of M. Sandwiching a thin switching Co layer between two Au layers should, thus, reduce its demagnetizating field. To look for this effect we made nanopillars of Co/Au/Co(t)/Au with Co thickness t = 1, 2, 3 and 4 nm, and measured magnetoresistances and switching currents. We will compare the switching currents of these nanopillars with those for Co/Cu/Co/Cu nanopillars. [1] J.A, Katine et. al., Phys.Rev. Lett. 84, 3149 (2000).}