Many of the intriguing electronic properties exhibited by transition metal compounds with partially filled d electron orbitals originate in a competition between many-body states with diff erent spin\, orbital and charge ordering patterns. Synchrotron-based r esonant x-ray diffraction (RXD) combines the unique ability to directl y probe all active degrees of freedom - charge\, spin and orbital - wi th the advantage of being element-specific. It is thus well suited for the investigation of the complex electronic states of d electr on systems.
\n \nThe talk will give an overview of our r ecent studies on 4d electron ruthenium-based oxides and 5d electron iridium-based sulfides\, which were carried out using the RXD technique. In particular\, we will discuss the discovery of a new orbital ordering transition between two paramagnetic phases in the lay ered Mott insulating system Ca2-xSrxRuO4 [1]\, the determination of the complex magnetic structure of its b ilayered counterpart Ca3Ru2O7 [2]\, a s well as the determination of the long-discussed magnetic structure of the superconducting magnet RuSr2GdCu2O8< /sub> [3]. The results from our ongoing\, still unpublished work on th e spinel compound CuIr2S4 [4] further demonstrat e the power of RXD in unraveling the exciting physics of strongly corr elated electron systems.
\n \nReferences:
\n
\n[
1] I. Zegkinoglou\, J. Strempfer\, C.S. Nelson\, J.P. Hill et al.\, Ph
ys. Rev. Lett. 95\, 136401 (2005)
\n[2] B. Bohnenbuck\, I. Zegkino
glou\, J. Strempfer\, C. Schuessler-Langeheine\, C.S. Nelson et al.\,
Phys. Rev. B 77\, 224412 (2008)
\n[3] B. Bohnenbuck\, I. Zegkinogl
ou\, J. Strempfer\, C.S. Nelson et al.\, Phys. Rev. Lett. 102\, 037205
(2009)
\n[4] I.Zegkinoglou\, V. Kiryukhin\, Ph. Leininger\, M.W.
Haverkort et al.\, in preparation
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