Uni Hamburg Fachbereich Physik
Logo STM/SPSTM, SPM-Group, Institute of Applied Physics, Hamburg

STM/SPSTM on Magnetic Nanostructures

Resolving spin structures at the atomic level

Fe-islands on W(110) - click to see animated flight (mpeg)

Nowadays, the use of topographic and spectroscopic modes of the scanning tunneling microscope (STM) almost routinely allows the correlation of local structural with electronic properties down to the atomic scale. By using a magnetic probe tip the STM can be made sensitive to the spin of the tunneling electrons.

The basic working principle is well-known as spin-valve effect: since any ferromagnetic material exhibits a spin imbalance at the Fermi-level EF and the electron spin has to be preserved in an elastic tunneling process the conductivity of a tunnel junction must depend on the relative magnetization direction between tip and sample.

Our aim is the further development of spin-polarized scanning tunneling microscopy and spectroscopy (SP-STM/STS). For this purpose we use non-magnetic probe tips which are coated by a thin (typically < 10 atomic layers) film of magnetic material. This enables to measure both the in-plane as well as the out-of-plane magnetization component of the sample, respectively. The smallest magnetic features observed so-far were domain walls with a width of 0.6 nm in ferromagnetic iron films in W(110) and the atomic scale antiferromagnetic structure of a manganese monolayer.