Resonant and magnetic x-ray scattering on strongly correlated electron systems: theory and experiments

by Prof. Luigi Paolasini (European Synchrotron Radiation Facility, France)

Wednesday 28 May 2008, 16:00 → 17:30 Europe/Rome

aula Conversi (Dip. di Fisica - Edificio G. Marconi)

Resonant X-ray Scattering (RXS) is an experimental method combining high-Q resolution x-ray elastic diffraction and atomic core-hole spectroscopy for investigating electronic and magnetic long-range ordered structures in condensed matter. The fundamental idea of RXS is that the incident photon energy, tuned across an absorption edge, is sufficient to cause a core-level electron to be injected to a partially filled valence band shell and to subsequentely decay through the emission of an elastically scattered photon with particular polarization dependence. The special nature of this process is that it is both electron shell and element specific, and it has introduced species sensitivity directly into the determination of magnetic structures. During recent years the development of theoretical models to RXS amplitudes have opened a new field of investigation in the domain of strongly correlated electron systems. Today, the separation of the RXS signal in terms of electromagnetic multipoles is one of the most fashionable ways to classify these experiments and opens new perspectives in this research field RXS technique has been essential in a number of high-profile cases, as for example the interplay between orbital charge and magnetic ordering in manganites and cuprates, the detection of high order magnetic and charge multipoles in Mott-Hubbard insulator V2O3, the studies of complex magnetic structures in multiferroics. The evolution of experimental techniques, which include the control and analysis of linear and circular photon polarization and the introduction of extreme environment conditions such as low temperatures, high magnetic field and high pressures, and the advance in theoretical interpretation of resonant x-ray scattering experiments make these synchrotron radiation studies at the forefront of the modern scattering techniques.