Dr. André Kubetzka

Spinpolarisierte Rastertunnelmikroskopie an magnetischen Nanostrukturen: Fe/W(110)

Andre Kubetzka, Hamburg, 25.1.1999

Die Aufgabe dieser Diplomarbeit bestand im Umbau eines Rastertunnelmikroskops für die Durchführung spinpolarisierter Rastertunnelmikroskopie und -spektroskopie. Dazu wurde ein Spitzenwechselmechanismus entwickelt und in das Mikroskop integriert. Das Mikroskop wurde zusammen mit einem Kryostaten in einer neuen Vakuumkammer installiert und diese an ein bestehendes UHV-System angeschlossen.

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Spinpolarisierte Rastertunnelmikroskopie an magnetischen Nanostrukturen: Fe/W(110)

Andre Kubetzka, Hamburg, 29.4.2002

In this work spinpolarized scanning tunneling microscopy and spectroscopy (SP-STM/-STS) is employed to investigate magnetic nanostructures and ultrathin films at low temperatures and in ultrahigh vacuum. The main subject is the system Fe/W(110), which, in the coverage regime of about two atomic layers Fe, exhibits a surprising complexity of magnetic domain structures. This complexity arises from the films' nanostructure, as well as from their intrinsic magnetic properties. SP-STM proves to be an ideal tool for characterisation, since structural, electronic, and magnetic properties can be investigated simultaneously on the nanometer scale and correlated directly.

Along with ferromagnetic tips, for the first time antiferromagnetic tips are employed, which, due to their vanishing stray field, solve the problem of an influence on the sample, and thereby enable the investigation of soft magnetic materials and superparamagnetic particles. Furthermore, it is shown that even nonmagnetic tips allow an imaging of domain walls, since the walls locally modify the electronic structure of the surface. Finally, an antiferromagnetic monolayer Mn/W(110) is imaged, which demonstrates that SP-STM has ultimately a resolution at the atomic scale. 

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