  We present electrical measurements of high-frequency magnetic dynamics
excited by spin-polarized currents in Co/Cu/Ni80Fe20 nanopillar devices, with a
magnetic field applied perpendicular to the sample layers. As a function of
current and magnetic field, the dynamical phase diagram contains several
distinguishable precessional modes and also static magnetic states. Using
detailed comparisons with numerical simulations, we provide rigorous tests of
the theory of spin-transfer torques.
