Spin-Motive Forces and Electron-Electron Interactions
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- Institutt for fysikk 
In this thesis, the spin-motive force, a spin-dependent force arising due to magnetization dynamics in an inhomogenous magnetic system, is investigated. We consider how spin-currents, arising from the spin dependent force, are altered by electron-electron interactions. The first part of the work reviews how the spin-motive forces can be understood. Two approaches are presented. First, we explain how the the spin-force arises from a specific gauge transformation creating effective electric fields. Then, we show how this same force can be related to the Berry curvature in a semi-classical model. The second part of the thesis investigates the influence of Coulomb interactions on a magnetic many-particle system. The magnetization is assumed to vary adiabatically in time and space. The interacting quantum mechanical problem is simplified by using a mean-field approximation, while the spin-motive force is treated as a perturbation in the form of a spin-dependent potential. The time dependent Hartree-problem is then solved to the first order in the perturbation. Based on the results, we formulate the system's charge and current response to a self-consistent field. The associated response functions are approximated and the resulting effects are calculated for a domain wall in an isotropic nano-wire.We further demonstrate that the induced charge and currents fulfill a continuity equation, as should be expected. While our approach is mathematically correct, it does not solve the desired physical problem because of subtle, implicit linear response assumptions. These assumptions are discussed.In concluding our work, we suggest an alternative approach that appears promising for solving the real physical transport problem.