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Magnetism, spin-orbit coupling, and electric field driven physics: Model studies from first principles (ab-initio)

Samir Abdelouahed, Institut d’Electronique, de Microélectronique, et de Nanotechnologie (Villeneuve d’Ascq)

Séminaire LCPQ

Salle de cours IRSAMC

Using the full potential linear augmented plane waves (FLAPW), we investigated different aspects of the electronic structure of magnetic, paramagnetic, metallic, or oxides materials.
The results we obtained including the intra-atomic coulomb interaction U (LDA(GGA)+U) for the 4f electrons produce the best agreement with experiment, meaning that taking into account the electronic correlations is necessary to describe correctly the electronic structure of strongly localized electrons materials. The results we obtained from our XMCD implementation reproduce the experimental results, namely the XMCD spectra and the XMCD-sum rules derived moments. XMCD is therefore a useful technique in characterizing magnetic properties of strongly localized electrons materials.
A key issue in spin electronics is the manipulation of the electron’s spins by an electric field.
This goal can be achieved for example by the magnetoelectric coupling in a multiferroic or by tunable strength of the Rashba spin-orbit (SO) coupling of surface states in adlayers of heavy elements, e.g., Bi(111), Bi/Ag(111). We have proposed a new route for manipulating the Rashba splitting of surface states: While keeping a Bi adlayer, we use the BaTiO3(001) substrate, in place of a metallic substrate. In this case, Bi-6p states exhibit the highest Rashba SO-splitting effect found so far. This effect stems from the potential gradient of the substrate and evidences the possibility of manipulating the latter effect by an external electric field.
Although the actual implementation of DFT has lead to a good understanding of a large class of materials, its application to more realistic materials is suffering from the computational effort/resources limitation.