We present the progress of the Milano-Bicocca PRIN  Research Unit (RU), where a numerical code for the calculation of spin-polarized, angle-resolved core-valence-valence Auger spectra was developed and applied to bulk and surface magnetic systems. The spin polarization of the emitted electrons from 3d impurities in simple metal hosts in a core-valence-valence Auger process is analyzed in terms of a first-principles density-functional theory approach, by using the golden rule. The relationship between the spin-dependent local density of states, the magnetic moments of the 3d atoms and the energy-dependent and total spin polarization of the Auger electrons is discussed. It is shown how to estimate the magnetic moment of the impurities from a measure of the total spin polarization of the Auger electrons. This can be achieved considering (i) that the Auger signal is simply due to the impurities only, (ii) the very locality of the Auger phenomenon, and (iii) a simple and general relationship between the spin polarization and the magnetic moment of the impurity which we show to be independent of the metal host. Spin selectivity in angle-resolved Auger photoelectron coincidence spectroscopy (AR-APECS) is used to probe electron correlation in ferromagnetic thin films measured by the RUs of RomaTre and Trieste. In particular, exploiting the AR- APECS capability to discriminate Auger electron emission events characterized by valence hole pairs created either in the high or in the low total spin state, a strong correlation effect in the MVV Auger lineshape of Fe/Cu(001) thin films was detected. Theoretical simulations allow one to ascribe this effect to interactions within the majority spin sub band. Such an assignment follows from a close comparison of the experimental AR-APECS lineshapes with the predictions of a model based on spin polarized density functional theory and the Cini-Sawatzky approach.
Theory and first principle calculation of CVV Auger spectra of magnetic systems / G. Fratesi, M.I. Trioni, G.P. Brivio. ((Intervento presentato al convegno Magnetic order in nanostructures and spectroscopy tenutosi a Roma nel 2012.
|Titolo:||Theory and first principle calculation of CVV Auger spectra of magnetic systems|
|Data di pubblicazione:||13-set-2012|
|Settore Scientifico Disciplinare:||Settore FIS/03 - Fisica della Materia|
|Citazione:||Theory and first principle calculation of CVV Auger spectra of magnetic systems / G. Fratesi, M.I. Trioni, G.P. Brivio. ((Intervento presentato al convegno Magnetic order in nanostructures and spectroscopy tenutosi a Roma nel 2012.|
|Appare nelle tipologie:||14 - Intervento a convegno non pubblicato|