Interplay of covalency, spin-orbit coupling, and geometric frustration in the d3.5 system Ba3LiIr2O9

Abstract

The electronic and magnetic properties of ${d}^{3.5}$ iridate ${\mathrm{Ba}}_{3}{\mathrm{LiIr}}_{2}{\mathrm{O}}_{9}$ have been studied using first-principles electronic structure calculations. The results of the calculations reveal that the system lies in an intermediate spin-orbit coupling (SOC) regime. There is strong covalency of $\mathrm{Ir}\ensuremath{-}5d$ and $\text{O}\ensuremath{-}2p$ orbitals. SOC, together with covalency, conspires to reduce the magnetic moment at the Ir site. By calculating the hopping interactions and exchange interactions, it is found that there is strong antiferromagnetic intradimer coupling within an ${\mathrm{Ir}}_{2}{\mathrm{O}}_{9}$ unit and other antiferromagnetic interdimer interactions make the system frustrated. The anisotropic magnetic interactions are also calculated. The calculations reveal that the magnitude of the Dzyaloshinskii-Moriya interactions parameter is small for this system. The magnetocrystalline anisotropy energy is large for this system and the easy axis lies on the $ab$ plane.