Neutron scattering study of correlated phase behavior in Sr2IrO4

Neutron diffraction measurements exploring the magnetic and structural phase behaviors of the candidate J(eff) = 1/2 Mott insulating iridate Sr2IrO4 are presented. 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-layer and bilayer Srn+1IrnO3n+1 systems are remarkably similar and suggest comparable correlation strengths in each system. DOI: 10.1103/PhysRevB.87.144405