HiSORセミナー
Combined Grazing-Incidence X-ray diffraction and Hard X-ray photoelectron spectroscopy study of La0.7Ca0.3MnO3/SrTiO3(001) thin films
日時 2015年10月26日 （月） 15：00～16：00 15：30～16：30
時間が変更になりました
場所 放射光科学研究センター 2階 セミナー室
講師 Germán R. Castro
(SpLine Spanish CRG BM25 Beamline at the ESRF, and Instituto de Ciencia de Materiales de Madrid-ICMM/CSIC)
Material composites, which combine different materials mostly multilayer thin films, with specific and defined properties, are a promising way to create products with specific properties. La1-xCaxMnO3-type (LCMO) perovskite-manganese oxides exhibit a wide variety of interesting physical properties which originate from mutual coupling among spin, charge and lattice degrees of freedom. The La1-xCaxMnO3-type perovskite-manganese oxides are strongly correlated electron systems and exhibit, in the Ca doping range between 0.15 and 0.5, a ferromagnetic-paramagnetic (F-M) phase transition accompanied by a metal-insulator (M-I) transition that results in a colossal magneto-resistance behaviour. In bulk La0.7Ca0.3MnO3 (LCMO), the transition temperature TFM, TMI rises for 33% Ca doping level reaching values close to room temperature. The degraded magnetic and conductivity properties at the interface, known as dead-layer behaviour, constitute an important drawback for industrial applications. Photoemission spectroscopies play a preponderant role in the study of the electronic properties of matter.
At SpLine, the Spanish CRG beamline at the ESRF the European Synchrotron, we operate a novel and exceptional set-up that combine Hard X-ray Photoelectron Spectroscopy (HAXPES) and X-ray diffraction (X-ray Reflectivity, Surface X-ray Diffraction, Grazing Incidence X-ray Diffraction and reciprocal space maps). Both techniques can be operated simultaneously on the same sample and using the same excitation source. In this talk, I will present a study of a series of epitaxial La0.7Ca0.3MnO3 (LCMO) films grown on SrTiO3(001). The film thickness range between 2.4 and 27 nm. The atomic and electronic structures, as well as the oxygen content, are followed simultaneously by GIXRD and HAXPES. Combining GIXRD, HAXPES and transport techniques, we have established a correlation between the electronic, atomic and transport properties on La0.7Ca0.3MnO3 thin films as a function of the thickness. Consequently two possible models are proposed that could explain the anomalous behaviour of the magneto-transport and the absence of TC and TMI for ultra-thin LCMO films.
