Structural investigation of the bilayer iridate Sr3Ir2O7

TL;DR

This study determines the precise monoclinic crystal structure of Sr3Ir2O7 using neutron diffraction and second harmonic generation, clarifying its symmetry and local Ir environment in this spin-orbit Mott insulator.

Contribution

The paper provides the first complete structural solution for Sr3Ir2O7, resolving previous ambiguities and identifying its correct space group as C2/c through combined experimental and theoretical methods.

Findings

Sr3Ir2O7 has a monoclinic symmetry (C2/c).

The correct structure explains weak neutron scattering violations.

The local symmetry of Ir4+ ions is clarified.

Abstract

A complete structural solution of the bilayer iridate compound Sr3Ir2O7 presently remains outstanding. Previously reported structures for this compound vary and all fail to explain weak structural violations observed in neutron scattering measurements as well as the presence of a net ferromagnetic moment in the basal plane. In this paper, we present single crystal neutron diffraction and rotational anisotropy second harmonic generation measurements unveiling a lower, monoclinic symmetry inherent to Sr3Ir2O7 . Combined with density functional theory, our measurements identify the correct structural space group as No. 15 (C2/c) and provide clarity regarding the local symmetry of Ir 4+ cations within this spin-orbit Mott material.