Neutron scattering study of correlated phase behavior in Sr2IrO4

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Neutron diffraction measurements are presented exploring the magnetic and structural phase behaviors of the candidate Jeff=1/2 Mott insulating iridate Sr₂IrO₄. Comparisons are drawn between the correlated magnetism in this single layer system and its bilayer analog Sr₃Ir₂O₇ where both materials exhibit magnetic domains originating from crystallographic twinning and comparable moment sizes. Weakly temperature dependent superlattice peaks violating the reported tetragonal space group of Sr₂IrO₄ are observed supporting the notion of a lower structural symmetry arising from a high temperature lattice distortion, and we use this to argue that moments orient along a unique in-plane axis demonstrating an orthorhombic symmetry in the resulting spin structure. Our results demonstrate that the correlated spin order and structural phase behaviors in both single and bilayer Srₙ₊₁IrₙO₃ₙ₊₁ systems are remarkably similar and suggest comparable correlation strengths in each system.