Influence of the Oersted field in the dynamics of spin-transfer microwave oscillators

This paper focuses on the magnetization dynamics induced by the balance between the physical positive damping and the negative induced by spin-transfer torque in point-contact devices. We consider an applied field perpendicular to the device plane which both saturates the magnetization of the free layer and tilts the one of the pinned layer about 30 degrees out-of-the-film plane. The influence of the nonuniform current-induced magnetic (Oersted or Ampere) field on the magnetization dynamics of such oscillators has been taken into account within a micromagnetic framework. Results of micromagnetic calculations show that the Oersted field yields spatial asymmetries in the magnetization configuration, which do not introduce any modifications in the frequency domain. Finally, Slonczewski's analytical formulation [J. Magn. Magn. Mater. 159, L1 (1996)] about the spatial geometry of the current-excited spin-wave modes has been validated numerically.