Research Group Solid State Spectroscopy and Magnetochemistry in Material Science.

Current Fields of Research.

General.

The research activities of the group focus on the spectroscopic and magnetic investigation of rare-earth and transition metal ions in diverse solids. Four topics can presently be identified:

• Glasses;
• Crystalline nano- or mesostructured materials;
• Spectroscopy and energy transfer in cubic hexachloro elapsolites;
• Molecular magnetism.

Different preparation methods are employed to obtain single crystals (crystal growth in solution, in silica gels, or by the Bridgman technique), crystalline and nanostructured materials (from solution or by hydrothermal synthesis) and glasses (from oxidic melts or by the modern Sol-Gel process). Using different experimental spectroscopic and magnetic techniques the co-ordination behaviour of the paramagnetic centres is investigated. The information obtained includes, for example, the symmetry and distortion of the co-ordination polyhedra, degree and type of metal-ligand interaction, evidence of exchange and/or superexchange interactions between neighbouring centres. The interpretation involves application of symmetry and group theoretical methods, semi-empirical models (e.g., based on crystal field theory), determination of crystal field and intensity (Judd-Ofelt) parameters, and magnetic exchange coupling constants.

Equipment and facilities of the Group.

• UV-VIS-NIR spectrometer (Omega 10, Bruins Instruments, fully computerised) for transparent materials in the 200-1500 nm range. A continuous flow helium cryostat (ROK-10, Leybold-Heraeus) can be attached to the spectrometer to cover the temperature range from 10 to 300 K.
• UV-VIS-NIRspectro-reflectometer with integrating sphere (DK 2A, Beckmann Instruments, interfaced to PC) for non-transparent materials in the 200-2500 nm range. A liquid nitrogen flow cryostat (CF-200, Oxford Instruments) can be attached to the integrating sphere to cover the temperature range from 77 to 300 K.
• IR spectrometer (325, Perkin Elmer, interfaced to PC) for IR transmission and reflection measurements in the 400-4000 cm^-1 region and the temperature range from 10 to 300 K.
• DC magnetic susceptometer (SUS-10, PAAR KG, interfaced to PC) operating from 0-1.4 Tesla within the 77-500 K range.
• AC/DC susceptometer, together with the research group Molecular Magnetism at the ICTOS at the Graz University of Technology (Model 7221, LAKE SHORE CRYOTRONICS, fully computerised) in the 0-1 Tesla range for DC and AC measurements. Temperature range 300-4.2 K.

Research Group Solid State Spectroscopy and Magnetochemistry in Material Science.