We report a single-crystal neutron diffraction study of the layered Sr2IrO4. This work unambiguously determines the magnetic structure of the system and reveals that the spin orientation rigidly tracks the staggered rotation of the IrO6 octahedra in Sr2IrO4. The long-range antiferromagnetic order has a canted spin configuration with an ordered moment of 0.208(3) μB/Ir site within the basal plane; a detailed examination of the spin canting yields 0.202(3) and 0.049(2) μB/site for the a axis and the b axis, respectively. It is intriguing that forbidden nuclear reflections of space group I41/acd are also observed in a wide temperature range from 4 K to 600 K, which suggests a reduced crystal structure symmetry. This neutron-scattering work provides a direct, well-refined experimental characterization of the magnetic and crystal structures that are crucial to the understanding of the unconventional magnetism exhibited in this unusual magnetic insulator.

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Published in Physical Review B, v. 87, issue 14, 140406, p. 1-6.

©2013 American Physical Society

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Research at ORNL's High Flux Isotope Reactor was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. The work at University of Kentucky was supported by NSF through Grants No. DMR-0856234 and No. EPS-0814194.