Regensburg 2002 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 22: Postersitzung III: Syst. korr. Elektr.: Theorie II (1-15), Metall-Isol.- und Phasenüberg
änge (16-33), SL: Massivmat., Bandl., Pinning, Vortexdyn., Transport, Korngr. (34-43), Niedrigdim. Syst., Magnetotransport (44-63)
TT 22.31: Poster
Donnerstag, 14. März 2002, 14:00–17:30, A
Orbital state, spin-obit coupling and phase transitions in ruthenates — •L.H. Tjeng1,2, T. Mizokawa2,3, G.A. Sawatzky2, G. Ghiringhelli4, O. Tjernberg4, N. B. Brookes4, H.-J. Lin5, C.T. Chen5, S. Schuppler6, H. Fukazawa7, S. Nakatsuji7 und Y. Maeno7,8 — 1II. Physikalisches Institut, Universität zu Köln — 2Solid State Physics Laboratory, University of Groningen, The Netherlands — 3Department of Complexity Science, University of Tokyo, Japan — 4ESRF, Grenoble, France — 5SRRC, Hsinchu, Taiwan — 6FZK, Karlsruhe — 7University of Kyoto, Japan — 8CREST-Saitama, Japan
The nature of the phase transitions in the Ca2−xSrxRuO4 system has been studied using O 1s x-ray absorption spectroscopy. For the Mott insulator CaRuO4, we have observed that the orbital population dramatically change with temperature. Together with our finding that a substantial orbital angular momentum is present in the Ru 4d band, we argue that the cooperation between the strong spin-orbit coupling and the small distortion of the RuO6 octahedra causes the interesting changeover of the spin and orbital anisotropy as a function of temperature.
For the x = 0.09 system, we have also observed a dramatic change in the orbital occupation across the metal-insulator transition. This occupation change is discontinuous and shows a hysteresis behavior. The possible relationship between orbital occupation, magnetic interactions and effective Coulomb interactions and bandwiths will be discussed.