Ab-initio approach to the stability and the structural, electronic and magnetic properties of the (001) Znfe2O4 surface terminations

We present a Density Functional Theory (DFT) based study of the structural and magnetic properties of the (001) surface of the semiconducting oxide ZnFe2O4 (spinel structure). The calculations were performed using the DFT based ab initio plane wave and pseudopotential method as implemented in the Quantum Espresso code. The all electron Full-potential linearized-augmented-plane-wave method (FP-LAPW) was also employed to check the reproducibility of the plane wave method. In both calculations the DFT+U methodology was employed and different (001) surface terminations of ZnFe2O4 were studied. We find that the surface terminated in Zn is the stable one. For all the (001) surface terminations our calculations predict that the Zn-Fe cationic inversion (anti-sites), which are defects in bulk ZnFe2O4, becomes stable and an integral part of the surface. Also, a ferrimagnetic behavior is predicted for the case of anti-sites in the superficial layer. Our results for different properties of the surface of ZnFe2O4 are compared with those obtained in bulk samples and those reported in the literature.