Regensburg 2010 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

MA: Fachverband Magnetismus

MA 12: FS: Single Nanomagnets

MA 12.3: Topical Talk

Dienstag, 23. März 2010, 11:45–12:15, H22

Stochastic resonance of a nanomagnet excited by spin transfer torque — •Ilya Krivorotov — Department of Physics & Astronomy, University of California, Irvine, California 92617, USA

Spin transfer torque from spin-polarized electrical current can excite large-amplitude magnetization dynamics in metallic ferromagnets of nanoscale dimensions. Since magnetic anisotropy energies of nanomagnets are comparable to the thermal energy scale, temperature can have a profound effect on the dynamics of a nanomagnet driven by spin transfer torque. We observe unusual types of microwave-frequency nonlinear magnetization dynamics co-excited by alternating spin transfer torque and thermal fluctuations in NiFe/Cu/Co spin valves of nanoscale dimensions. In these dynamics, temperature amplifies the amplitude of GHz-range precession of magnetization and enables excitation of highly nonlinear dynamical states of magnetization by weak alternating spin transfer torque. We explain these thermally activated dynamics in terms of non-adiabatic stochastic resonance of magnetization driven by spin transfer torque. We find that the non-adiabatic stochastic resonance of magnetization gives rise to strong enhancement of the rectified voltage generated by nanoscale spin valves in response to alternating spin current, and thus this type of magnetic resonance may find use in sensitive nanometer-scale microwave signal detectors.