On the possibility of incorporation of the iron impurity into $A$ sites in SrTiO$_3$

TL;DR

This study investigates the incorporation of iron impurities into SrTiO₃, revealing that high-temperature annealing enables up to 30% of Fe to occupy the $A$ sites, supported by experimental and first-principles evidence.

Contribution

It provides new insights into Fe site occupancy in SrTiO₃, combining spectroscopic analysis with theoretical calculations to understand impurity behavior.

Findings

Up to 30% of Fe enters $A$ sites at high annealing temperatures.

Fe at $A$ sites exhibits significant off-centering displacement.

Results align with first-principles calculations and previous dopant studies.

Abstract

The local environment and oxidation state of the Fe impurity in strontium titanate are studied using XAFS spectroscopy. The influence of annealing temperature and deviation from stoichiometry on the possibility of incorporation of the impurity into the $A$ and $B$ sites of the perovskite structure is studied. The results obtained from the X-ray diffraction, XANES spectra, and EXAFS spectra suggest that at high annealing temperature the iron atoms, at least partially (up to 30%), enter the $A$ sites in SrTiO$_3$. The obtained results agree with results of first-principles calculations, according to which the iron at the $A$ site exhibits strong off-centering (the displacement of $\sim$1 {\AA}), similar to that previously established in SrTiO$_3$ samples doped with Mn and Co.