Measurements of out-of-plane dynamics induced in magnetic nanopillars by spin transfer

Abstract

Electrical current can induce very large amplitude of precession in nanomagnets, resulting in highly nonlinear dynamical regimes unattainable by any other means of excitation. We performed spectroscopic measurements of magnetic nanodevices whose geometry was optimized for coherent dynamics at high currents. The dependence of the observed spectroscopic features on the direction of the magnetic field is consistent with the out-of-plane precessional mode, as confirmed by micromagnetic simulations. The dynamics are asymmetric with respect to the inversion of the field, which is highly unusual for magnetic phenomena not involving exchange bias. Micromagnetic simulations indicate that the asymmetry is likely caused by a combination of the Oersted field generated by the current and sample shape imperfections.