Feng Ye, Songxue Chi, Bryan C. Chakoumakos, Jaime A. Fernandez-Baca, Tongfei Qi, G. Cao
We report a single-crystal neutron diffraction study of the layered $\rm Sr_2IrO_4$. This work unambiguously determines the magnetic and crystal structures, and reveals that the spin orientation rigidly tracks the staggered rotation of the IrO6 octahedra in $\rm Sr_2IrO_4$. The long-range antiferromagnetic order has a canted spin configuration with an ordered moment of 0.208(3) $\mu_B$/Ir site within the basal plane; a detailed examination of the spin canting yields 0.202(3) and 0.049(2) $\mu_B$/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 existent in this unusual magnetic insulator.
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http://arxiv.org/abs/1302.2890
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