Berlin 2005 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique
TT 16.77: Poster
Samstag, 5. März 2005, 11:00–16:30, Poster TU C
Co3+ spin state transition detected by phonon Raman scattering in GdBaCo2O5.5 — •Yu.G. Pashkevich1, V.P. Gnezdilov2, P. Lemmens3,4, B. Keimer4, C. Ambrosch-D raxl5, K.V. Lamonova1, A.A. Gusev1, K.-Y. Choi6, S.N. Barilo7, S.-V. Shiryaev7, and G.-L. Bychkov7 — 1A.A. Galkin Donetsk Phystech NASU, 83114 Donetsk, Ukraine — 2B.I. Verkin Inst. for Low Temp. Physics NASU, 61164 Kharkov, Ukraine — 3Inst. for Physics of Condensed Matter, TU Braunschweig, D-38106 Braunschweig, Germany — 4MPI-FKF, D-70569 Stuttgart, Germany — 5Inst. für Theoretische Physik, Universität Graz, A-8010 Graz, Austria — 6Inst. for Materials Research, Tohoku University, Sendai 980-8577, Japan — 7Inst. of Physics of Solids & Semiconductors, Academy of Sciences, 220072 Minsk, Belarus
The change of the spin state of Co3+ as function of temperature or pressure is an intriguing feature of cobalt-based perovskite compounds. In the layered cobaltites RBaCo2O5O5.5 this problem is rather complicated due to the octahedral and opened square pyramidal coordinations of Co with oxygen. Raman spectroscopy can provide information about subtle changes in spin state through detecting changes of the phonon spectra, which are sensitive to the O-Co-O bonding length and angles. Raman spectra of single crystal GdBaCo2O5O5.5 were measured in the temperature range 5 - 400 K and remarkable changes of frequencies and intensities were observed. Frequencies and eigenvectors of Raman active phonon modes have been defined using frozen phonon ab initio band structure calculations and structural data at 300 K in Pmmm setting.