Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 77: Methods: Scanning Probe Techniques I

O 77.4: Vortrag

Donnerstag, 28. Februar 2008, 16:15–16:30, MA 041

Fe/W(001) - a structurally, electronically and magnetically inhomogeneous system studied by force microscopy — •Rene Schmidt, Ung Hwan Pi, Alexander Schwarz, and Roland Wiesendanger — Institute of Applied Physics, University of Hamburg, Jungiusstr. 11, 20355 Hamburg

Since force microscopy detects all kinds of electromagnetic forces simultaneously, imaging of inhomogeneous samples is particularly challenging. We studied Fe films of around 1.3 atomic layers epitaxially grown on W(001), which are in this respect a prototypical sample system, as the structural, electronic and magnetic properties differ between first and second layer. Iron grows pseudomorphically on W(001) whereby the layers are highly strained. When imaging the surface, an electrostatic contrast with bias dependent apparent step heights can be observed, which is related to different work functions of first and second layer. Kelvin Probe Force Microscopy allows to map the work function and to measure the correct topography. Interestingly, we found that even on the same layer, different work functions are observed. Moreover, the first and second layer are magnetically different. The first layer is antiferromagnetically ordered, while double layers are ferromagnetic. As a result, a magnetostatic contrast from double layer islands is visible at relatively large tip-sample distances with ferromagnetic tips, while no magnetic signal is obtained on monolayer areas. However, at small separations the antiferromagnetic c(2x2) structure of the iron monolayer can be resolved by detecting the short-ranged magnetic exchange force between tip and sample.