Berlin 2012 – wissenschaftliches Programm

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MI: Fachverband Mikrosonden

MI 4: 100 years since the Laue experiment: Topical aspects of diffraction and scattering (Joint Session KR, BP, DF, GP, MA, MI, MM; related to SYXD)

MI 4.7: Vortrag

Dienstag, 27. März 2012, 11:30–11:45, EMH 225

Theory of Electron Magnetic Circular Dichroism — •Jan Rusz — Dept. of Physics and Astronomy, Uppsala University, Sweden

Electron magnetic circular dichroism (EMCD) is an electron microscopy analogue of the established x-ray magnetic circular dichroism, that can provide atom-specific spin and orbital moments. EMCD, compared to its x-ray counterpart, offers a potential of significantly better spatial resolution, potentially in the Angstrom range. Presently, the technique is limited by difficulties of reaching sufficient signal to noise ratio and complexity of the accompanying dynamical diffraction effects, both of which make quantitative analysis demanding and prone to systematic errors.

We present recent theoretical developments in the field of EMCD, namely, 1) influence of plural scattering and associated spectral post-processing corrections; 2) convergence of the dynamical diffraction calculations in electron energy loss spectroscopy (ELNES), and 3) decomposition of the signal in diffraction plane to maps of various irreducible operators, such as orbital and spin magnetic moments, number of holes, orbital and spin-orbital anisotropy tensors.

These developments improve our understanding of deviations of recent quantitative EMCD experiments from expected values, allow more accurate predictions of the signal distribution, and uncover the wealth of information contained in electron energy loss spectra and thus aid in improving the methods of extraction of the magnetic signal from experimental datasets.