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MA: Fachverband Magnetismus

MA 9: Spin Excitations/Spin Torque

MA 9.7: Vortrag

Montag, 16. März 2015, 17:15–17:30, H 0112

Spin-transfer torque effects in the dynamic forced response of the magnetization of nanoscale ferromagnets in superimposed ac and dc bias fields in the presence of thermal agitation — •William Coffey¹, Yuri Kalmykov², Sergey Titov³, Declan Byrne¹, and Jean Wegrowe⁴ — ¹Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland — ²Université de Perpignan Via Domitia, Laboratoire de Mathématiques et Physique, F-66860, Perpignan, France — ³Kotelnikov Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, Vvedenskii Square 1, Fryazino, Moscow Region, 141120, Russia — ⁴Laboratoire des Solides Irradiés, Ecole Polytechnique, 91128 Palaiseau Cedex, France

Spin-transfer torque (STT) effects on the stationary forced response of nanoscale ferromagnets driven by an ac magnetic field of arbitrary strength in the presence of thermal fluctuations are investigated via the generic nanopillar model of a spin-torque device. The STT effects are treated via the magnetic Langevin equation generalized to include the Slonczewski STT term thereby extending the statistical moment method to the forced response. Hence, the dynamic susceptibilities, frequency-dependent dc magnetization, dynamic hysteresis loops, etc. are evaluated for arbitrary ac field direction, strength and spin polarization, highlighting STT effects on both the low-frequency thermal relaxation processes and the high-frequency ferromagnetic resonance, demonstrating a pronounced dependence of such characteristics on the spin polarization current, allowing interpretation of STT experiments.