Structure-Related Electronic and Magnetic Properties in Ultrathin Epitaxial Ni_xFe_3−xO₄ Films on MgO(001)

Abstract

Off-stoichiometric NixFe3−xO4 ultrathin films (x 3O4 to NiFe2O4 is observed, whereas local transformation into NiO structures is observed for films with Ni content x > 1. However, angle-resolved hard X-ray photoelectron spectroscopy measurements indicate homogeneous cationic distributions without strictly separated phases independent of the Ni content, while X-ray absorption spectroscopy shows that also for x > 1, not all Fe2+ cations are substituted by Ni2+ cations. The ferrimagnetic behavior, as observed by superconducting quantum interference device magnetometry, is characterized by decreasing saturation magnetization due to the formation of antiferromagnetic NiO parts.

Keywords

• nickel ferrite
• ultrathin films
• strain-property relation
• disordererd phase
• synchrotron radiation
• X-ray diffraction