  The performance of manganite-based magnetic tunnel junctions (MTJs) has
suffered from reduced magnetization present at the junction interfaces that is
ultimately responsible for the spin polarization of injected currents; this
behavior has been attributed to a magnetic "dead layer" that typically extends
a few unit cells into the manganite. X-ray magnetic scattering in resonant
conditions (XRMS) is one of the most innovative and effective techniques to
extract surface or interfacial magnetization profiles with subnanometer
resolution, and has only recently been applied to oxide heterostructures. Here
we present our approach to characterizing the surface and interfacial
magnetization of such heterostructures using the XRMS technique, conducted at
the BEAR beamline (Elettra synchrotron, Trieste). Measurements were carried out
in specular reflectivity geometry, switching the left/right elliptical
polarization of light as well the magnetization direction in the scattering
plane. Spectra were collected across the Mn L2,3 edge for at least four
different grazing angles in order to better analyse the interference phenomena.
The resulting reflectivity spectra have been carefully fit to obtain the
magnetization profiles, minimizing the number of free parameters as much as
possible. Optical constants of the samples (real and imaginary part of the
refractive index) in the interested frequency range are obtained through
absorption measurements in two magnetization states and subsequent
Kramers-Kronig transformation, allowing quantitative fits of the magnetization
profile at different temperatures. We apply this method to the study of
air-exposed surfaces of epitaxial La2/3Sr1/3MnO3 (001) films grown on SrTiO3
(001) substrates.

Strongly Correlated Electrons;Materials Science