The atomic structure along step edges on metal oxide surfaces is crucial for the growth of overlayers in complex oxide devices. No experimental techniques are yet capable of resolving that structure. Theoretical calculations of step structures on metal oxides are complex and have not been reported to date.
By taking into account both the ionic and covalent components of chemical bonding in metal oxides, we have developed a method for predicting the relative stability of different step structures. Fe3O4 (magnetite) is a ferrimagnetic metal that is of interest for spintronics applications and as a substrate for growing complex oxides. Scanning tunneling microscopy observations on Fe3O4 (100) surfaces show alternating smooth and jagged step structures, as shown above. By evaluating the number of bonds and excess charge of step ions, we can predict the most probable arrangement of positive and negative ions along the step edges.