Micromagnetic Simulation for Spin-Transfer Switching With a Tilted Spin Polarizer

This paper reports the micromagnetic simulations of spin-wave modes excited by spin-transfer torque for an elliptical nanomagnet sized 178 × 133 × 2.1 nm³. Through power spectral analysis we discovered that, for the collinear case, the excited spin-wave mode exhibits the same spatial symmetry as the initial ground state. The additional action of the Oersted field not only changes the mode pattern but also shifts the eigenfrequency from 8.24 GHz to 2.99 GHz due to the degradation of symmetry. For the non-collinear case, without taking into account the Oersted field, a tilted polarizer leads to the excitation of the quasi-uniform mode and reduces the switching time substantially. However, considering the Oersted field, the activated mode is the center mode. The simulated results indicate that the spatial symmetry of the Oersted field and the spin-torque term play crucial roles in determining the activated spin-wave eigenmodes.