Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 14: Spin Systems and Itinerant Magnets

TT 14.13: Talk

Tuesday, March 27, 2007, 17:45–18:00, H19

Orbitally Ordered Phase in Ca_2−xSr_xRuO₄ Investigated with Resonant X-ray Diffraction — •Ioannis Zegkinoglou¹, Joerg Strempfer², Britta Bohnenbuck¹, Christie S. Nelson³, John P. Hill³, Jonathan C. Lang⁴, George Srajer⁴, Yoshiteru Maeno⁵, and Bernhard Keimer¹ — ¹Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany — ²HASYLAB at DESY, Hamburg, Germany — ³Brookhaven National Laboratory, New York, USA — ⁴APS at Argonne National Laboratory, Argonne, USA — ⁵Department of Physics, Kyoto University, Japan

Resonant x-ray diffraction at the Ru L_II and L_III absorption edges was used to investigate the interplay between the spin, lattice and orbital degrees of freedom in the layered 4d-electron Ca_2−xSr_xRuO₄ system [1]. A new orbital ordering phase transition was discovered in single-crystal compounds with Sr-doping x=0 and x=0.1 at temperatures 260 K and 130 K, respectively, at reciprocal space positions (100) and (011). The orbital order is only weakly coupled to the lattice. Its propagation vector is not affected by the change of the low-temperature antiferromagnetic structure upon Sr substitution. The tilt order of the RuO₆ octahedra was also probed in our studies. It produces resonant scattering at the structurally and magnetically forbidden (110) position and follows a different temperature dependence from orbital order.

[1] I. Zegkinoglou et al., Phys. Rev. Lett. 95, 136401 (2005)