Ab initio investigation of structure, magnetism and ferroelectricity and their interplay in multiferroic bulk materials and films

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In the past years, magnetoelectronics and spintronics have emerged as a very activeand promising field of exploratory research and developed as a new paradigm ofnanoelectronics where, besides the charge, also the spin of an electron or the magnetizationof a material is used as a new degree of freedom for information storage orprocessing. Relevant novel multifunctional metal-oxide tunnel junctions for future deviceslike 4- or even 8-bit memory require the use of multiferroic materials which exhibita magnetic and an electric polarization simultaneously. Emphasis is put on multiferroictunnel junctions consisting of ferromagnetic leads and ferroelectric oxides or multiferroicoxides as barriers. A theoretical understanding of such junctions and materials requirescomputer simulations of phenomena related to their structural, chemical and electroniccomplexity, in bulk, films and junctions. We use density-functional theory to explore thedependence of the electronic structure of multiferroic bulk materials and films onchemical composition, structural relaxation, dimensionality, and temperature, with thegoal of predicting novel multiferroic materials with improved functionality.