Electron Diffraction, Coherence, Magnetic and Spectroscopic Properties of Novel Materials
||Electron Diffraction, Coherence, Magnetic and Spectroscopic Properties of Novel Materials|
||Jan Rusz <email@example.com>|
||Uppsala University, Department of Physics and Astronomy|
||2014-08-04 – 2015-01-01|
Recent progresses with manipulating electron beam in transmission electron microscopes opened new frontiers of research. Use of the electron vortex beams, that is beams that carry an orbital angular momentum, brings a promise of measuring atom-specific magnetic moments at atomic resolution. Biprism with a Boersch plate prepares the electron beam as a coherent superposition of two convergent electron beams with tunable relative phase shift, also aiming to simplify the measurements of electron magnetic circular dichroism. Spin polarized electron beams will soon lead to pioneering new experimental techniques relying on spin-spin interactions between the sample and the probe beam. In order to maximize the output of these novel experimental techniques, we stress the demand for substantial progress in the theoretical understanding of the probe-sample interaction processes, which include fundamental questions related to interplay of dynamical diffraction effects, coherence of the probe beam, spin-dependent electronic transitions, relativistic effects and dynamical effects of the core-hole on the local electronic structure. Within this project we aim to address these challenges. The working tools will be state-of-the-art methods based on first principles calculations, high-performance computing and analytical models. Applications will include simulations of proof-of-concept experiments on magnetic samples utilizing vorticity, spin-polarization and coherence of the beam.
In addition to the research in the area of transmission electron microscopy, we will continue our efforts in 1) searching for replacement materials for permanent magnet applications and 2) studies of electronic and optical properties of semiconductor nano-structures.
Replacement materials for permanent magnet applications should contain little or none of rare-earth elements. Their magnetism should mostly originate from cheap 3d transition elements. The determining quantity is saturation magnetization, magnetic transition temperature and magneto-crystalline anisotropy energy. Especially the latter requires demanding simulations based on density functional theory. We will perform simulations for a wide range of alloys, in an effort to find optimized material compositions as candidates for cheap permanent magnets.
Semiconductor nano-structures, such as core-shell nanostructures or nanoparticles embedded in host matrices, are used in a variety of optical devices. Their dimensions being in the nano-range offer a tuning parameter, by which we can dramatically influence their electronic structure and optical properties - utilizing so called quantum confinement effect. We will perform simulations of various semiconductor nanostructures with an effort to understand and predict their optical properties.