Effect of epitaxial strain on the cation distribution in spinel ferrites CoFe2O4 and NiFe2O4: a density functional theory study

TL;DR

This study uses density functional theory to explore how epitaxial strain influences cation distribution in spinel ferrites CoFe2O4 and NiFe2O4, revealing strain-dependent preferences for cation arrangements and supporting the existence of short-range B site order.

Contribution

It provides the first detailed theoretical analysis of epitaxial strain effects on cation distribution in these ferrites, highlighting the sensitivity of cation inversion to strain and growth conditions.

Findings

NiFe2O4 favors cation inversion more strongly than CoFe2O4.

Tensile strain reduces the tendency for cation inversion.

Significant energy differences suggest short-range B site order in NiFe2O4.

Abstract

The effect of epitaxial strain on the cation distribution in spinel ferrites CoFe2O4 and NiFe2O4 is investigated by GGA+U total energy calculations. We obtain a very strong (moderate) tendency for cation inversion in NiFe2O4 (CoFe2O4), in agreement with experimental bulk studies. This preference for the inverse spinel structure is reduced by tensile epitaxial strain, which can lead to strong sensitivity of the cation distribution on specific growth conditions in thin films. Furthermore, we obtain significant energy differences between different cation arrangements with the same degree of inversion, providing further evidence for recently proposed short range B site order in NiFe2O4.