"Images of a Spin-Torque-Driven Magnetic Nano-Oscillator"

X. W. Yu: V. S. Pribiag, Y. Acremann, A. A. Tulapurkar, T. Tyliszczak, K. W. Chou, B. Bräuer, Z.-P. Li, O. J. Lee, P. G. Gowtham, D. C. Ralph, R. A. Buhrman, and J. Stöhr; Phys. Rev. Lett., 04/21/11.

Additional Authors: V. S. Pribiag, Y. Acremann, A. A. Tulapurkar, T. Tyliszczak, K. W. Chou, B. Bräuer, Z.-P. Li, O. J. Lee, P. G. Gowtham, D. C. Ralph, R. A. Buhrman, and J. Stöhr

Abstract:

We present the first space- and time-resolved images of the spin-torque-induced steady-state oscillation of a magnetic vortex in a spin-valve nanostructure. We find that the vortex structure in a nanopillar is considerably more complicated than the 2D idealized structure often-assumed, which has important implications for the driving efficiency. The sense of the vortex gyration is uniquely determined by the vortex core polarity, confirming that the spin-torque acts as a source of negative damping even in such a strongly nonuniform magnetic system. The orbit radius is ∼10  nm, in agreement with micromagnetic simulations.