Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 14: Spin Systems and Itinerant Magnets

TT 14.15: Vortrag

Dienstag, 27. März 2007, 18:15–18:30, H19

Investigation of Magnetic and Orbital Order in Ca₃Ru₂O₇ using Resonant X-ray Diffraction — •Britta Bohnenbuck¹, Jörg Strempfer², Ioannis Zegkinoglou¹, Christie Nelson³, and Bernhard Keimer¹ — ¹Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany — ²HASYLAB at DESY, Notkestrasse 85, 22605 Hamburg, Germany — ³National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973-5000, USA

We used resonant x-ray diffraction at the L_II- and L_III- absorption edges of Ru to investigate the bilayered transition metal oxide Ca₃Ru₂O₇. This system shows metallic antiferromagnetism between the metal to insulator transition T_MI=48K and the antiferromagnetic ordering temperature T_N=56K. In order to learn more about the magnetic and orbital degrees of freedom we performed azimuthal and polarization studies on high quality single crystals both below and above T_MI at various reciprocal space positions. Our results are consistent with the magnetic structure proposed by neutron experiments. The magnetic moments are coupled ferromagnetically within the ab-planes but antiferromagnetically between adjacent planes. We also observe a reorientation of the magnetic moment in the ab-plane at T_MI. This coincides with a drastic intensity decrease of the magnetic reflection, which vanishes completely at T_N. Our diffraction studies do not give any indication for antiferroorbital order in Ca₃Ru₂O₇. However, there might be ferroorbital order as proposed recently by Raman spectroscopy.