Abstract:
Images obtained by the scanning tunnelling microscope (STM) together with curves yielded by the scanning tunnelling spectroscopy (STS) allow us to uncover the structure of solid surfaces on the atomic scale. Unfortunately, the interpretation of the experimental results is often ambiguous. A careful theoretical analysis is then needed to resolve the ambiguities. As examples of such analyses, I am going to present theoretical studies based on first-principles calculations for two types of solid surfaces. The first example is the (001) surface of a Fe64Ni36 alloy (the Invar) The STM image of the surface has been related to the surface buckling, while the most prominent feature of the STS has been explained in terms of an surface electronic resonance. The other type of surfaces I am going to deal with are disordered magnetic overlayers of 3d metals (V, Cr, Mn, Fe, or Co) on the tungsten (001) substrate - either submonoatomic films of the 3d metals or monoatomic layers of two-dimensional binary alloys consisting of these metals. In the case of the 3d metallic overlayers on W(001), the emphasis of the theoretical analysis is going to be on their intricate magnetic properties, which also offer an ideal opportunity for an application of a spin-polarized STM.