Incipient orbital order in half-metallic Ba2FeReO6

Interplay between Spin-Orbital Coupling and Electron-Correlation: Induction of Phase Transitions and Giant Magnetic Anisotropy in Strained LaSr_{1−x}Ca_xNiReO_6

In recent decades, 3d-5d based double perovskite oxides (DPO) have received considerable attention due to the existence of the Mott-insulating (MI) state, which is owing to the spin-orbit coupling (SOC)...

Double perovskite heterostructures: magnetism, Chern bands, and Chern insulators

Experiments demonstrating the controlled growth of oxide heterostructures have raised the prospect of realizing topologically nontrivial states of correlated electrons in low dimensions. Here, we study heterostructures consisting of {111} bilayers of double perovskites separated by inert band insulators. In bulk, these double perovskites have well-defined local moments interacting with itinerant electrons leading to high temperature ferromagnetism. Incorporating spin-orbit coupling in the two-dimensional honeycomb geometry of a {111} bilayer, we find a rich phase diagram with tunable ferromagnetic order, topological Chern bands, and a C=±2 Chern insulator regime. Our results are of broad relevance to oxide materials such as Sr_{2}FeMoO_{6}, Ba_{2}FeReO_{6}, and Sr_{2}CrWO_{6}.

Spin-electron-phonon excitation in Re-based half-metallic double perovskites

A remarkable hardening (~30 cm(-1)) of the normal mode of vibration associated with the symmetric stretching of the oxygen octahedra for the Ba(2)FeReO(6) and Sr(2)CrReO(6) double perovskites is observed below the corresponding magnetic ordering temperatures. The very large magnitude of this effect and its absence for the antisymmetric stretching mode provide evidence against a conventional spin-phonon coupling mechanism. Our observations are consistent with a collective excitation formed by the combination of the vibrational mode with oscillations of Fe or Cr 3d and Re 5d occupations and spin magnitudes.

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.