Institute for Theoretical Physics • University of Cologne

Spin-polarized scanning tunneling microscopy at low temperature (8 K) and in high magnetic fields (6 T) is a powerful technique to investigate magnetic properties of individual nanoscale objects ranging in size form single atoms to several thousand atoms. I focus on the magnetization reversal and the spin-dependent electronic properties of bilayer Co, Fe-decorated Co and Fe islands on Cu(111). We find a novel noncollinear, helical magnetic order in the Fe islands, which is identified by a magnetic stripe contrast with a period of 1.28 nm. The high spatial resolution of the scanning tunneling spectroscopy reveals the significance of structural and electronic relaxation for the magnetic anisotropy and the spin-dependent transport properties of single islands. In an outlook I present first results from our new STM, which operates at 0.3 K in a vector magnetic field, on superconductivity of Pb monolayers and on the proximity effect.