Epitaxial growth and structure of cobalt ferrite thin films with large inversion parameter on Ag(001).

Cobalt ferrite ultrathin films with the inverse spinel structure are among the best candidates for spin filtering at room temperature. High-quality epitaxial CoFeO films about 4 nm thick have been fabricated on Ag(001) following a three-step method: an ultrathin metallic CoFe alloy was first grown in coherent epitaxy on the substrate and then treated twice with O, first at room temperature and then during annealing. The epitaxial orientation and the surface, interface and film structure were resolved using a combination of low-energy electron diffraction, scanning tunnelling microscopy, Auger electron spectroscopy and in situ grazing-incidence X-ray diffraction.

Simulation of Surface Resonant X-ray Diffraction.

We present an ab initio numerical tool to simulate surface resonant X-ray diffraction experiments. The crystal truncation rods and the spectra around a given X-ray absorption edge are calculated at any position of the reciprocal space. Density functional theory is used to determine the resonant scattering factor of an atom within its local environment and to calculate the diffraction peak intensities for surfaces covered with a thin film or with one or several adsorbed layers.

Strain driven monoclinic distortion of ultrathin CoO films in the exchange-coupled CoO/FePt/Pt(0 0 1) system.

The structure and strain of ultrathin CoO films grown on a Pt(0 0 1) substrate and on a ferromagnetic FePt pseudomorphic layer on Pt(0 0 1) have been determined with in situ and real time surface x-ray diffraction. The films grow epitaxially on both surfaces with an in-plane hexagonal pattern that yields a pseudo-cubic CoO(1 1 1) surface. A refined x-ray diffraction analysis reveals a slight monoclinic distortion at RT induced by the anisotropic stress at the interface.

Self-organized ultrathin FePt nanowires produced by glancing-angle ion-beam codeposition on rippled alumina surfaces.

Ultradense macroscopic arrays of ferromagnetic alloy nanowires exhibit unique properties that make them attractive both for basic physics studies and for prospective nanodevice applications in various areas. We report here on the production of self-organized equiatomic FePt nanowires produced by glancing-angle ion-beam codeposition on alumina nanoripple patterns at room temperature and subsequent annealing at 600 °C. This study demonstrates that periodically aligned FePt nanowires with tunable size (∼10-20 nm width and ∼0.

Energy-dispersive X-ray absorption spectroscopy at LNLS: investigation on strongly correlated metal oxides.

An energy-dispersive X-ray absorption spectroscopy beamline mainly dedicated to X-ray magnetic circular dichroism (XMCD) and material science under extreme conditions has been implemented in a bending-magnet port at the Brazilian Synchrotron Light Laboratory. Here the beamline technical characteristics are described, including the most important aspects of the mechanics, optical elements and detection set-up. The beamline performance is then illustrated through two case studies on strongly correlated transition metal oxides: an XMCD insight into the modifications of the magnetic properties of Cr-doped manganites and the structural deformation in nickel perovskites under high applied pressure.

Linear and circularly polarized light to study anisotropy and resonant scattering in magnetic thin films.

The remarkable polarization properties of synchrotron light have lead to the advent of modern synchrotron-related spectroscopic studies with angular and/or magnetic selectivity. Here an overview is given of the prominent aspects of the polarization of the light delivered by a bending magnet, and some dichroic properties in X-ray absorption spectroscopy (XAS). Two studies developed at the Brazilian Synchrotron Light Laboratory are then reported, exemplifying the profit gained using linear and circular polarization of X-rays for the study of magnetic thin films and multilayers.