Spintronics is a new branch of electronics in which the electron spin in addition to charge is manipulated at the nano- and atomic level. Spintronic devices are promising elements to be possibly used in quantum computers and quantum communication based on electronic solid-state devices. Thus, spintronics is believed to strongly influence the perspectives of information in the nearest future. A class of materials which has been considered for spintronic applications is the one of half metals. In principle, due to the fact that the Fermi energy of one spin direction lies in a gap, the current in a half metallic ferromagnet is completely spin polarized. Because of this complete polarization, layered structures containing half metallic ferromagnets can exhibit large magnetoresistence promising great advantages for a variety of device applications. Therefore the HMF is an important class of materials to be investigated. The present research project contributes significantly to the construction and application of new theoretical techniques to investigate spintronic materials in order to understand their finite-temperature behavior and explain some technically important characteristics like multifunctionality and tunable properties. Realistic predictions for these materials can be made on the basis of their electronic structure using Density Functional Theory within the Local Density Approximation, DFT-LDA, in combination with different many-body approaches to deal with their electronic correlations. A large number of encouraging results have been obtained combining the DFT-LDA material-specific calculations, with Dynamical Mean Field Theory, DMFT, which takes into account local correlations. However, in order to characterize the finite-temperature behavior, which is mainly determined by magnetic excitations, a theory which captures non-locality is required. Among the already known techniques extending the locality of DMFT, Extended DMFT, GW+DMFT, CDMFT and others, a new approach, the variational cluster perturbation theory V-CPT, was introduced recently. On the methodological grounds, the current project aims at implementing the self-consistent V-CPT, as a faster and reliable solver of the many body problem in combination with the DFT-LDA approach. In the applicative part of the project, we mainly address the issues of finite-temperature polarization, magneto-optical properties and quantum transport in spintronic materials based on HMF. Apart from increasing the fundamental knowledge in the field of material science, the computational schemes developed in this project will give quantitative explanations and predictions necessary to design future electronic devices based on HMF.
|Tatsächlicher Beginn/ -es Ende||1/01/06 → 31/12/09|