Beiträge auf der Frühjahrstagung 2005:2001-2002-2003-2004-2005-2006-2007-2008-2009-2010 - 2011 - 2012 - 2013 - 2014 |
TT 21.8 | Vortrag | Symposium Frustrierte Spinsysteme |
Raman spectroscopy on frustrated spin systemsPeter Lemmens, Inst. for Physics of Condensed Matter, TU
Braunschweig, D-38106 Braunschweig, Germany and MPI for Solid State
Research, D-70569 Stuttgart, Germany Many transition metal oxides realize competing interactions based on
spin, charge or orbital degrees of freedom (1). Raman scattering has
contributed to the understanding of this interplay and the effect of
frustration to a great extend due to its unprecedented sensitivity,
resolution
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TT 16.76 | Poster |
Co3+ spin state transition detected by phonon Raman scattering in GdBaCo2O5.5Yu.G. Pashkevich1, V.P. Gnezdilov2, K.-Y. Choi3, P. Lemmens4;5, B. Keimer5, C. Ambrosch-Draxl6, S.N. Barilo7, S.-V. Shiryaev7, and G.-L. Bychkov7 1 A.A. Galkin Donetsk Phystech NASU, 83114 Donetsk, Ukraine 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 de¯ned using frozen phonon ab initio band structure calculations and structural data at 300 K in Pmmm setting. |
TT 16.75 | Poster C |
Low temperature mixed spin state of Co3+ in LaCoO3 evidenced from local lattice distortions
V. Gnezdilov1, P. Lemmens2,3, Yu.G. Pashkevich4,
K.-Y. Choi5, S. Shiryaev6, G. Bychkov6,
and S. Barilo6 Single- and multi-phonon excitations of the single crystalline LaCoO3 were studied using Raman spectroscopy in the temperature region of 5 K
-300 K. First-order Raman spectra show a larger number of phonon modes
than allowed for the rhombohedral (D6 3d) structure. Additional phonon |
TT 16.52 | Poster C |
Magnetic structure of DyBaCo2O5.5
•H. Luetkens1, H.-H. Klauss2, A. Bosse2,
D. Cheptiakov3, S. Streule3, E. Pomjakushina3,
1 Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut CH-5232
Villigen PSI, Switzerland
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MA 5.6 | Vortrag |
Angular dependent absorption spectroscopy of a de-twinned DyBaCo2O5.5
single crystal
Myrsini Lafkioti1, Stefan Gold1, Eberhard Goering1,
Gisela Schütz1, Joachim The Perovskite DyBaCo2O5.5 exhibits a very rich phase
diagram including two different paramagnetic, a ferromagnetic, and an
antiferromagnetic phase as a function of temperature[1]. In addition to
these unusual properties, the system exhibits a very pronounced and
strong magnetocrystalline anisotropy, with the easy axis along the
crystallographic a-axis[2]. We will show detailed angular and
temperature dependent X-ray magnetic circular dichroism and nonmagnetic
linear polarized absorption spectroscopy results at the Co L2,3
and O K edges, performed |