Effect of non-magnetic impurities on the magnetic states of anatase TiO$_2$

TL;DR

This study uses ab initio calculations to explore how non-magnetic impurities like N and F affect the electronic and magnetic properties of TiO$_2$, revealing induced magnetic moments and changes in electronic states.

Contribution

It provides a detailed analysis of magnetic states induced by N and F doping in TiO$_2$, highlighting the evolution of electronic properties and the origin of magnetism.

Findings

N-doping induces magnetic moments at N and neighboring O sites.

F-doping creates magnetic moments at Ti atoms.

Electronic structure evolves from semiconductor to metal with doping.

Abstract

The electronic and magnetic properties of TiO$_2$, TiO$_{1.75}$, TiO$_{1.75}$N$_{0.25}$, and TiO$_{1.75}$F$_{0.25}$ compounds have been studied by using \emph{ab initio} electronic structure calculations. TiO$_2$ is found to evolve from a wide-band-gap semiconductor to a narrow-band-gap semiconductor to a half-metallic state and finally to a metallic state with oxygen vacancy, N-doping and F-doping, respectively. Present work clearly shows the robust magnetic ground state for N- and F-doped TiO$_2$. The N-doping gives rise to magnetic moment of $\sim$0.4 $\mu_B$ at N-site and $\sim$0.1 $\mu_B$ each at two neighboring O-sites, whereas F-doping creates a magnetic moment of $\sim$0.3 $\mu_B$ at the nearest Ti atom. Here we also discuss the possible cause of the observed magnetic states in terms of the spatial electronic charge distribution of Ti, N and F atoms responsible for bond formation.