The activities of the X-ray Absorption and Magnetic Scattering Group are very diverse, covering the structural, magnetic and electronic properties of materials. For this chapter we have selected three main areas: X-ray absorption fine structure, with particular emphasis on chemistry; X-ray magnetic circular dichroism studies with an emphasis on magnetic multilayers and impurities; and X-ray magnetic scattering. Since many of the research interests of the group extend to other beamlines and groups there are also contributions from BM20 (the ROBL CRG beamline) and the Theory Group. There were many other highly-interesting studies done on the Group's beamlines in the past year that we were not able to include here. For interested readers, we have tried to reference some of this work in the short introductions to each section. For example, several articles could equally have illustrated the very high sensitivity of X-ray magnetic circular dichroism to nano-scale magnetism. For instance the study by Gambardella et al. [1] of cobalt nano-wires on platinum stepped surfaces (Figure 42) revealed new insight into their magnetic properties.


Fig. 42: Scanning Tunnel Microscope (STM) topograph of the Pt(997) surface. Cobalt monatomic chains decorate the platinum step edges (the vertical dimension is enhanced for better contrast). The chains are linearly aligned and have a spacing equal to the terrace width.

There are also several interesting studies that fall outside the scope of the sections below. In particular, there have been important developments in experimental methods. One such example is spin-resolved X-ray absorption spectroscopy, with a very interesting application to EuO [2]. Another example is an extension of the X-ray resonant Raman scattering technique to allow, through the application of sum rules, the determination of high-order moments in ferromagnetic materials [3].


[1] P. Gambardella et al. Nature 416, 301 (2002).
[2] P. G. Steeneken et al. PRL 88, 047201 (2002).
[3] L. Braicovich et al. PRL (to be published).