Intermediate state switching dynamics in magnetic double layer   nanopillars grown by molecular beam epitaxy
  We observe a stable intermediate resistance switching state in the current perpendicular to plane geometry for all Co/Cu/Co double layer nanopillar junctions grown by molecular beam epitaxy. This novel state has a resistance between the resistances of the parallel and antiparallel alignment of both Co-layer magnetizations. The state, which originates from an additional in-plane magnetic easy axis, can be reached by spin transfer torque switching or by an external magnetic field. In addition to spin torque-induced coherent small-angle spin wave modes we observe a broad microwave emission spectrum. The latter is attributed to incoherent magnetic excitations that lead to a switching between the intermediate state and the parallel or antiparallel alignment of both ferromagnetic layers. We conclude that the additional magnetic easy axis suppresses a stable trajectory of coherent large-angle precession, which is not observed in our samples. 
N. M\"usgens, T. Maassen, E. Maynicke, S. Rizwan Ali, A. Heiss, R.   Ghadimi, J. Mayer, G. G\"untherodt, and B. Beschoten
cond-mat.mes-hall cond-mat.mtrl-sci