SEMINAR
Tuesday,
28th
October^{ }2003  h. 14:30
Aula A1
P. Ferriani
INFM, National
Research Center on Nanostructures and Biosystems at Surfaces (S3),
Unita’ di Ricerca di Modena and Dipartimento di Fisica, Univ. di Modena
e Reggio Emilia
ANGLE
RESOLVED RESONANT INELASTIC XRAY SCATTERING: INTENSITY AND DICHROISM
FROM 3d TRANSITION METALS IN SPECIAL GEOMETRIES
Abstract
Resonant inelastic xray scattering is an element selective
experimental technique that emerged as an extremely powerful tool for
investigating electronic and magnetic ground state properties of
strongly correlated electron systems. We are particularly interested in
the process involving the L3 threshold in the absorption and the 3s _
2p transition in the emission. A theoretical study of the cross section
and of its dependence on the geometrical setup of the experiment and
on the incident photon polarization, that is of the outmost importance
for interpreting the experimental results, is presented here. With the
choice of the perpendicular geometry for the incoming photon and by
scanning the angular dependence of the outcoming photon, it is possible
to obtain important information concerning the ground state, such as
the multipole moments of the charge and magnetic densities, even of
high order. We provide a detailed description about the angular
dependence of the dichroism and unpolarized signals. The unusual case
where the emission direction is out of the plane containing the
direction of the incident photon and the sample magnetization is also
analysed. In this case an asymmetry for emission with respect to this
plane, which is linked to the magnetic structure of the system, is
observed. This new result supplies a test for the applicability of the
socalled fast collision approximation, necessary in order to extract
the multipole moments of the system by measuring the angular dependence
of the magnetic circular dichroism in the resonant scattering process.
Numerical calculations on 3d transition metal systems, based on
multiplet atomic model with the inclusion of the appropriate crystal
and magnetic field, are given.
