Spin-dependent transport in inhomogeneous systems

In this project, we investigate the coupling of the spin degree of freedom with electronic degrees of freedom across interfaces in ferromagnetic multilayers on the ultrafast time scale. For this purpose, we consider the excitation of the ferromagnetic material by a femtosecond laser pulse. The so created spin-polarized electrons with large energies respond to the applied field which is reflected in the longitudinal and transverse transport coefficients. We consider mainly the energy-dependent transversal transport properties, that are related to the anomalous and the spin Hall effect. In particular, we are interested in the time and spatial dependence of the charge- and spin-current distribution with respect to the interface. On the other hand, we investigate timedependent spin currents that are produced by the spin Hall effect if a THz electric field is applied to the nonmagnetic metal layer. Propagation of this spin current into the ferromagnetic layer causes a spin-transfer torque on the magnetization. Based on an ab initio description in combination with a semi-classical Boltzmann theory we aim at understanding the charge and spin current distributions on nanometer length scales and ultrafast time scales.