  The growth of Fe nanoclusters on the Ge(001) surface has been studied using
lowtemperature scanning tunnelling microscopy (STM) and density functional
theory (DFT) calculations. STM results indicate that Fe nucleates on the
Ge(001) surface, forming wellordered nanoclusters of uniform size. Depending on
the preparation conditions, two types of nanoclusters were observed having
either four or sixteen Fe atoms within a nanocluster. The results were
confirmed by DFT calculations. Annealing the nanoclusters at 420 K leads to the
formation of nanorow structures, due to cluster mobility at such temperature.
The Fe nanoclusters and nanorow structures formed on the Ge(001) surface show a
superparamagnetic behaviour as measured by X-ray magnetic circular dichroism.
