Role of disorder in the electronic and magnetic properties of Ag$_3$LiIr$_2$O$_6$

TL;DR

This study investigates how structural disorder and hybridization influence the electronic and magnetic properties of Ag$_3$LiIr$_2$O$_6$, revealing the persistence of a relativistic $j_{eff} = 1/2$ state and reproducing observed magnetic order through ab initio models.

Contribution

It demonstrates that the $j_{eff} = 1/2$ model remains valid for Ag$_3$LiIr$_2$O$_6$ and highlights the role of disorder and vacancies in explaining experimental spectra and magnetic order.

Findings

The $j_{eff} = 1/2$ model is applicable to Ag$_3$LiIr$_2$O$_6$.

Disorder and Ag vacancies influence the electronic structure and spectra.

The observed antiferromagnetic spiral order is reproduced by ab initio magnetic models.

Abstract

The nature of magnetism in the intercalated honeycomb iridate Ag$_3$LiIr$_2$O$_6$ has been a subject of recent intensive debate, where the absence or presence of antiferromagnetic order has been reported to be related to possible structural disorder effects and, an enhanced Ir-O hybridization and itinerancy with respect to the parent Li$_2$IrO$_3$ has been suggested as the origin of distinct x-ray spectroscopy features. In the present work we investigate the microscopic nature of the electronic and magnetic properties of Ag$_3$LiIr$_2$O$_6$ via a combination of density functional theory combined with exact diagonalization of ab initio-derived models for various experimental and theoretical structures. We evaluate two possible scenarios, the itinerant quasimolecular framework (QMO) on the one hand, and the localized relativistic $j_{\rm eff} = 1/2$ and $j_{\rm eff} = 3/2$ picture on the other hand, and find that the latter description is still viable for this system. We further calculate resonant inelastic x-ray scattering spectra and show that agreement with experimental observations can be obtained if the presence of Ag vacancies leading to changes in Ir filling and structural disorder is assumed. Finally, we show that the experimentally observed antiferromagnetic spiral magnetic order is reproduced by our ab-initio derived magnetic models.