  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.
