Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 22: Spin Dynamics / Spin Torque III
MA 22.5: Vortrag
Donnerstag, 25. März 2010, 10:45–11:00, H10
Spin shot noise and spin torque dynamics — •Jacek Swiebodzinski1, Alex Kamenev2, Thomas Dunn2, Daniela Pfannkuche3, and Alexander Chudnovskiy3 — 1Theoretische Physik, Universität Duisburg-Essen, 47048 Duisburg, Germany — 2Department of Physics, University of Minnesota, Minneapolis, Minnesota 55455, USA — 3I. Institut für Theoretische Physik, Universität Hamburg, 20355 Hamburg, Germany
Investigations of noise in nano-scale devices are indispensable in any use-oriented consideration and - at the same time - a broad and fascinating field from the basic-researcher’s point of view. In this theoretical contribution we investigate the role of spin shot noise in spin torque dynamics of mono-domain ferromagnets. Spin shot noise is a consequence of the discreteness of angular momentum transfer and present in any spin torque experiment. At low temperatures it gives the dominant contribution to magnetization noise. Unlike its thermal counterpart the nonequilibrium noise displays a dependence on the relative orientation of the ferromagnets forming the magnetic junction. We address the question of spin torque switching by applying a generalized Fokker-Planck approach that models switching rates with the help of an effective temperature in the Arrhenius factor. We show that the spin shot noise leads to a renormalization of the effective temperature. The details of the renormalization depend on the geometry of the system. In particular, the nonequilibrium noise may lead to the occurrence of ”cold” and ”hot” trajectories of the magnetization vector with respect to the noise intensity.