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Fe Nanoclusters on the Ge(001) Surface Studied by Scanning Tunneling Microscopy, Density Functional Theory Calculations and X-Ray Magnetic Circular Dichroism

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.