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Antiferromagnetic order and domains in Sr_{3}Ir_{2}O_{7} probed by x-ray resonant scattering

DOI: 10.1103/PhysRevB.85.184432 DOI Help

Authors: S. Boseggia (Diamond Light Source) , R. Springell (University College London, U.K.) , H. Walker (ESRF, France) , A. T. Boothroyd (University of Oxford) , D. Prabhakaran (University of Oxford, U.K.) , D. Wermeille (XMaS, UK-CRG, ESRF, France) , L. Bouchenoire (ESRF) , S. P. Collins (Diamond Light Source) , D. F. Mcmorrow (University College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 85 (18)

State: Published (Approved)
Published: May 2012
Diamond Proposal Number(s): 6629

Abstract: We report on a detailed x-ray resonant scattering study of the bilayer iridate compound Sr 3 Ir 2 O 7 at the Ir L 2 and L 3 edges. Resonant scattering at the Ir L 3 edge has been used to determine that Sr 3 Ir 2 O 7 is a long-range ordered antiferromagnet below T N ?230K with an ordering wave vector q=(12 ,12 ,0) . The energy resonance at the L 3 edge was found to be a factor of ?30 times larger than that at the L 2 edge. This remarkable effect has been seen in the single-layer compound Sr 2 IrO 4 and has been linked to the observation of a J eff =12 spin-orbit insulator. Our result shows that despite the modified electronic structure of the bilayer compound, caused by the larger bandwidth, the effect of strong spin-orbit coupling on the resonant magnetic scattering persists. Using the program sarah , we have determined that the magnetic order consists of two domains with propagation vectors k 1 =(12 ,12 ,0) and k 2 =(12 ,?12 ,0) , respectively. A raster measurement of a focused x-ray beam across the surface of the sample yielded images of domains of the order of 100?m , with odd and even L components, respectively. Fully relativistic, monoelectronic calculations using the Green's function technique for a muffin-tin potential have been employed to calculate the relative intensities of the L 2,3 edge resonances, comparing the effects of including spin-orbit coupling and the Hubbard U term. A large L 3 to L 2 edge intensity ratio (?5 ) was found for calculations including spin-orbit coupling. Adding the Hubbard U term had no significant effect on the calculated spectra.

Journal Keywords: Transition Metal Oxide; Spin-Orbit Coupling; Magnetic Domains; Iridates

Subject Areas: Physics, Materials, Chemistry

Instruments: I16-Materials and Magnetism

Other Facilities: ESRF