Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 34: Correlated Electrons: Spin Systems and Itinerant Magnets

TT 34.8: Talk

Friday, March 31, 2006, 12:00–12:15, HSZ 301

Investigation of Orbital and Magnetic Order in Ruthenates with Resonant X-ray Diffraction — •Ioannis Zegkinoglou¹, J. Strempfer¹, B. Bohnenbuck¹, C.S. Nelson², C. Bernhard¹, and B. Keimer¹ — ¹Max-Planck-Institut für Festkörperforschung, D-70569 Stuttgart, Germany — ²National Synchrotron Light Source, Brookhaven National Laboratory, Upton, USA

Resonant x-ray diffraction at the L_II and L_III-absorption edges of ruthenium has been used to investigate orbital and magnetic order in 4d transition metal oxide single crystals. A large resonance enhancement of the magnetic scattering cross-section due to electric dipole transitions directly into the 4d band is observed. In the single-layered Mott transition system Ca₂RuO₄, a new phase transition between two paramagnetic phases is observed around 260 K, at the wave-vector characterizing the low-temperature antiferromagnetic order [1]. Based on the polarization and azimuthal angle dependence of the diffracted intensity, the new phase transition is attributed to the ordering of the Ru t_2g orbitals. In RuSr₂GdCu₂O₈, the antiferromagnetic order of Ru ions and the possible effect of the onset of superconductivity on it below T_c ≈ 40 K are investigated. Due to the sensitivity of resonant x-ray diffraction to the azimuthal angle, a precise determination of the direction of the magnetic moment in the system is possible.

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