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Synthesis, Raman scattering and infra-red spectroscopy investigations of correlated behaviour in transition metal oxyhalides

Final Activity Report Summary - OXYHALIDE MATERIALS (Synthesis, Raman scattering and infra-red spectroscopy investigations of correlated behaviour in transition metal oxyhalides)

The aim of the project was to study the structure and properties of magnetically and electrically active materials using Raman and infra-red spectroscopy techniques. The Intra-European Marie Curie fellowship allowed the recipient to move country and join the Condensed Matter Physics group at Chalmers University of Technology, Gothenburg, Sweden and undertake training through research. In particular an important objective of the project was training in Raman spectroscopy. The researcher made the materials in the department of Chemistry before performing the Raman measurements in the Physics department. Raman spectroscopy is a simple technique in principle. A laser light is shined onto the surface of the material and the light can interact with excitations such as vibrations in the material and lose or gain energy from these interactions. By studying these changes in the energy of the scattered light information about the structure and also magnetic properties of the sample can be obtained.

The most important scientific achievement made during the project was the characterisation of the structural changes that occur in the material Cd2Re2O7 on cooling it from room temperature to 10 K using Raman spectroscopy. On further cooling, to 1 K (-272 Degrees Celsius), this material becomes a superconductor, i.e. electrons can move in the material without any resistance. Understanding the structural behaviour of the material is vital to understand this property and our results allowed the first model explaining the structural changes to be developed. Another highlight of the project was the discovery of new materials of the form Sr1-xBixCoO3-y (0.1 x 0.2) e.g. Sr0.85Bi0.15CoO2.7. These materials have interesting structures made up of layers of CoO6 octahedra and CoO4 tetrahedra and when treated with oxygen gas they can absorb it and change structure.