Speaker: Yaroslaw Bazaliy, University of South Carolina
Abstract: Spin-transfer torque is a result of a non-equilibrium magnetic interaction induced by a flow of electric current. In nano-size devices spin transfer is a mechanism for current-induced magnetic switching, an effect with many applications in computer memory and logic. Calculations of critical switching currents were performed analytically and numerically for many systems. However, a clear physical interpretation of the results was available only in special cases. We firstly derive an invariant form of the current-induced switching condition and show that there exists a figure of merit for the current ability to destabilize a minimum of magnetic energy and induce switching. The resulting approach based on the "switching ability" of the current provides an intuitive physical picture of the switching behavior in devices of any geometry. We secondly consider the problem of current-induced stabilization of the saddle points and show that it happens via a different mechanism due to the topological restrictions. Saddle points are normally stabilized by a current-induced merger with other equilibria. Finally, we present and emerging full picture of possible switching scenarios in spin torque devices.