Effect of epitaxial strain on the cation distribution in spinel ferrites CoFe(2)O(4) and NiFe(2)O(4): A density functional theory study

Abstract

The effect of epitaxial strain on the cation distribution in spinel ferrites CoFe(2)O(4) and NiFe(2)O(4) is investigated by GGA+U total energy calculations. We obtain a very strong (moderate) tendency for cation inversion in NiFe(2)O(4) (CoFe(2)O(4)), 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 NiFe(2)O(4).