Non-equilibrium Green’s Function Methods for Spin Transport and Dynamics

The modeling of spintronic devices is a theoretical challenge, since one has to describe accurately both the electronic structure of the constituent materials and their charge- and spin-transport properties. In this chapter we present the state-of-the-art quantum transport theory appropriate for this task. The theory is based on the so-called non-equilibrium Green’s function formalism, which is combined with density functional theory in order to provide a first principles description of materials properties. This allows for the evaluation of the steady-state charge and spin current through a quantum system at a finite applied bias voltage between the electrodes. It also describes the spin-transfer torque that flowing spins exert on localized magnetic moments, which is able to switch the magnetization of a magnetic system. In this chapter the detailed discussion about the principal methodological aspects is accompanied by the review of a number of technologically relevant applications.