Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 7: Spin-Dynamics/ Spin-Torque II
MA 7.1: Vortrag
Montag, 23. März 2009, 15:15–15:30, HSZ 04
Phase-locking of dc current-driven vortex motion to an external signal — •Ronald Lehndorff1,2, Daniel E. Bürgler1, Zbigniew J. Celinski2, and Claus M. Schneider1 — 1Institut für Festkörperforschung und JARA-FIT, Forschungszentrum Jülich GmbH, D-52425 Jülich — 2Center for Magnetism and Magnetic Nanostructures, University of Colorado at Colorado Springs, CO, USA
The dynamics of magnetic vortices under the influence of magnetic fields and spin-transfer torque has recently been of great interest [1,2]. The gyrotropic motion of vortices, which is their lowest excitation mode, enables the realization of vortex-based spin-torque oscillators [3].
We study the vortex dynamics in nanopillars made of 20nm Fe/6nm Ag/2nm Fe. The 20nm thick Fe layer is structured to a circular disk of 230nm diameter. Due to its size and shape it can hold a magnetic vortex or an onion state. We excite both magnetic structures by dc currents and show that the vortex state is advantageous for the operation of a spin-torque oscillator. Additionally, we study the coupling of the vortex' dynamic mode to externally applied electric hf signals of different frequencies and amplitudes. The observed phase-locking is a prerequisite to achieve sufficient output power for applications since it enables the coupling of a large number of spin-torque oscillators.
[1] B. van Waeyenberge, et al., Nature 444, 461 (2006) [2] R. Hertel, et al., Phys. Rev. Lett. 98, 117201 (2007) [3] V.S. Pribiag, et al., Nature 438, 339 (2005)