New Approach to Spin Dynamics in Broken Inversion Symmetry

The equation describing spin dynamics has been modified since considering the effects of broken inversion symmetry, such as spin current and surface polarization, among others. Those effects, which are not expressed by the effective field, make spin dynamics complicated and difficult to understand. We investigated a new approach to model the spin dynamics in a system of broken inversion symmetry by introducing an asymmetric and directional spin-spin interaction and deriving the effective fields from them. We unified those effects into the original simple form of the Landau-Lifshitz equation using the effective fields. We believe that our model offers a new and more general approach towards understanding spin dynamics, one that effectively merges the Dzyaloshinskii-Moriya interaction, spin transfer torques and the Rashba effect into the Landau-Lifshitz equation. We discussed how our model is applied to spin dynamics and compared our approach with the traditional discussions on spin dynamics.