Optical studies of manganites, superconductors and laser materials - études optiques des manganite, supraconducteurs et matériaux laser

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Optical techniques such as inelastic light scattering, photoluminescence and infrared interferometry are very useful to develop fundamental science and to explain microscopic interactions in solids. We use these techniques to better understand the mechanisms and microscopic properties of: a)-recently discovered colossal magnetoresitance in manganites R(1-x)A(x)MnO3 (R = rare earth and A=Ba, Sr, Ca) where an unusually large change of resistivity is observed following the application of magnetic field. Such materials are on one hand interesting from a fundamental viewpoint since charge, spin and lattice ions are strongly coupled giving rise to numerous physical phenomena and phase transitions of current interest in condensed matter. On the other hand, they offer potential in magnetic recording media sensors and spin polarized electronics. b)-high critical temperature superconductors, e.g. R(2-x)Ce(x)CuO4, characterized by absence of resistance and perfect diamagnetism prevalence below Tc. They are important materials typically for current transport without losses, for high magnetic field generation and for devices that detect very weak magnetic fields. c)-rare earth based optical devices such as solid state lasers and optical memories obtained by doping oxides with rare earth ions (e.g. Nd: YVO4 and Yb:Y2SiO5).