Local geometry ofFe3+ions on the potassium sites inKTaO3

Abstract

We present the results of our computer-simulation study on the ${\mathrm{Fe}}^{3+}$ incorporation in ${\mathrm{KTaO}}_3$. We find that ${\mathrm{Fe}}^{3+}$ ions enter the crystal lattice by means of a self-compensation-type reaction, i.e., by creation of ${\mathrm{Fe}}_{\mathrm{K}}^{3+}$ and ${\mathrm{Fe}}_{\mathrm{Ta}}^{3+}$ substitutional defects. Moreover, an energetically feasible model reaction is suggested for the occurrence of both axial defect centers ${\mathrm{Fe}}_{\mathrm{Ta}}^{3+}$-${\mathrm{V}}_{\mathrm{O}}$ and ${\mathrm{Fe}}_{\mathrm{K}}^{3+\mathrm{-}}$ ${\mathrm{O}}_{\mathrm{I}}$. Finally, a superposition-model analysis, based on a Lennard-Jones-type radial b${\mathrm{¯}}_2$ function, shows that the ground-state axial zero-field splitting parameter of D=4.46 ${\mathrm{cm}}^{\mathrm{-}1}$, found experimentally, should be explained by ${\mathrm{Fe}}_{\mathrm{K}}^{3+\mathrm{-}}$ ${\mathrm{O}}_{\mathrm{I}}$. This result, supported by shell-model calculations, contradicts a prior superposition-model analysis.