Ab initio study of the TiO$_2$ Rutile(110)/Fe interface

Adsorption of Fe on the rutile (110)-surface is investigated by means of {\it ab initio} density functional theory calculations. We discuss the deposition of single Fe atoms, an increasing Fe coverage, as well as the adsorption of small Fe clusters. It is shown that the different interface structures found in experiment can be understood in terms of the adsorption of the Fe atoms landing first on the rutile surface. On the one hand, strong interface bonds form if single Fe atoms are deposited. On the other hand, the Fe-Fe bonds in deposited Fe clusters lead to a three-dimensional growth mode. Mainly ionic Fe-oxide bonds are formed in both cases and the electronic band gap of the surface is reduced due to interface states. Besides the structural and electronic properties, we discuss the influence of the interface on the magnetic properties finding stable Fe moments and induced moments within the interface which leads to a large spin polarization of the Fe atoms at the rutile (110)/Fe interface.