A critical point in Sr2-xIrO4 and less distorted IrO6 octahedra induced by deep Sr-vacancies

TL;DR

This study investigates how deep Sr-vacancies in Sr2-xIrO4 influence local structural distortions and electronic properties, revealing a critical point where less distorted IrO6 octahedra significantly alter spin-orbit coupling and magnetic behavior.

Contribution

It provides new insights into the relationship between Sr-vacancies, local structural distortions, and electronic properties in Sr2IrO4 using XAS techniques.

Findings

Sudden increase in branching ratio near the critical point

Less distorted IrO6 octahedra induced by Sr-vacancies

Altered spin-orbit coupling and electronic structure

Abstract

For the Sr2-xIrO4 system, recent work pointed out the abnormal electronic and magnetic properties around the critical point. Here, to understand Sr-vacancy effect on spin-orbit coupled Mott insulator Sr2IrO4, the electronic structure and local structure distortion for Sr2-xIrO4 system have been investigated by x-ray absorption spectroscopy (XAS). By comparing the intensity of white-line features at the IrL2,3-edge x-ray absorption near-edge spectroscopy (XANES), we observe a sudden rise of the branching ratio in the vicinity of the critical point.Further analysis on theIrL3 -edge extended x-ray absorption fine structure (EXAFS) and calculated data demonstrated that the abrupt enhancement of the branching ratio is intimately related to the less distorted IrO6 octahedra induced by deep Sr-vacancies, which in turn alters the relatively strength of the spin-orbit coupling (SOC) and crystal electric field (CEF)that would dictate the abnormal behavior of electronic and magnetic structure near the critical point.