In-plane antiferromagnetism in $Na_{0.5}CoO_2$ induced by $Sb_{Co}$ dopants

TL;DR

This study uses density functional theory to show that electron doping via $Sb_{Co}$ dopants in $Na_{0.5}CoO_2$ flips magnetic coupling from ferromagnetic to antiferromagnetic, revealing dopant site dependence.

Contribution

It demonstrates how specific dopants and their positions critically influence magnetic phases in $Na_{0.5}CoO_2$ using computational methods.

Findings

$Sb_{Co}$ doping induces antiferromagnetism in $Na_{0.5}CoO_2$

Interstitial $Cu_{Int}$ does not change magnetic coupling

Magnetic phase depends on dopant type and site

Abstract

$Na_xCoO_2$ has a fascinating and complex magnetic phase diagram that can be further manipulated by doping. Here, we investigated the effect of electron doping on the magnetic coupling among $Co^{4+}$ ions in $Na_xCoO_2$ using density functional theory based on Hartree-Fock hybrid functional. We found that electron doping through substitutional $Sb_{Co}$ dopants flip the in-plane ferromagnetic coupling among $Co^{4+}$ ions in the undoped compound to antiferromagnetic. Electron doping through interstitial $Cu_{Int}$, however, does not have a similar effect as $Cu_{Int}$ dopant leaves the compound ferromagnetic, just like the case of the undoped compound. The results demonstrate the critical dependence of magnetic phase in $Na_{0.5}CoO_2$ on the dopant and its incorporation site.