Dresden 2014 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 44: Spin Torque and Spin Excitations II
MA 44.2: Vortrag
Donnerstag, 3. April 2014, 15:15–15:30, HSZ 403
Linear and nonlinear stationary ac response of the magnetization of nanomagnets in the presence of thermal agitation and spin-transfer torques — D.J. Byrne1, •W.T. Coffey2, Y.P. Kalmykov3, and S.V. Titov4 — 1School of Physics, University College Dublin, Belfield, Dublin 4, Ireland — 2Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland — 3Université de Perpignan Via Domitia, Laboratoire de Mathématiques et Physique, F-66860, Perpignan, France — 4Kotelnikov Institute of Radio Engineering and Electronics of the RAS, Russia
Thermal fluctuations of nanomagnets driven by spin-polarized currents are treated via the Landau-Lifshitz-Gilbert equation generalized to include both the random thermal noise field and the Slonczewski spin-transfer torque term. The statistical moment method [Y. P. Kalmykov et al., Spin-torque effects in thermally assisted magnetization reversal: Method of statistical moments, Phys. Rev. B 88 (2013) 144406] for the study of out-of-equilibrium time independent observables of the generic nanopillar model of a spin-torque transfer (STT) device subjected to thermal fluctuations is extended to the stationary time dependent observables arising from applied a.c. field. The virtue of our solutions is that they hold for the most comprehensive formulation of the generic nanopillar model, i.e., for arbitrary directions of the external field and spin polarization and for arbitrary free energy density, yielding the STT switching characteristics under conditions otherwise inaccessible. Both the dynamic magnetic susceptibility and dynamic hysteresis are determined for an a.c. field of arbitrary strength.