Neutron scattering study of correlated phase behavior in Sr2IrO4

TL;DR

This neutron scattering study investigates the magnetic and structural phases of Sr2IrO4, revealing lower symmetry and similar correlated magnetic behaviors compared to its bilayer counterpart, indicating comparable correlation strengths.

Contribution

The paper provides new insights into the structural symmetry and magnetic order in Sr2IrO4, highlighting similarities with Sr3Ir2O7 and suggesting comparable correlation strengths in single and bilayer iridates.

Findings

Lower structural symmetry due to high temperature lattice distortion.

Moments orient along a unique in-plane axis, indicating orthorhombic symmetry.

Similar correlated spin order in single and bilayer systems.

Abstract

Neutron diffraction measurements are presented exploring the magnetic and structural phase behaviors of the candidate J$_{eff}=1/2$ Mott insulating iridate Sr$_2$IrO$_4$. Comparisons are drawn between the correlated magnetism in this single layer system and its bilayer analog Sr$_3$Ir$_2$O$_7$ 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 Sr$_2$IrO$_4$ 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 Sr$_{n+1}$Ir$_{n}$O$_{3n+1}$ systems are remarkably similar and suggest comparable correlation strengths in each system.