R. Chauvistré

Magnetic extended x-ray absorption fine structure at the edges of 3d elements

We report normal and magnetic extended x-ray absorption fine-structure (EXAFS) measurements made on 30 ML Fe films on Cu(001) substrates at the edges. The magnetic EXAFS at the L edges of 3d metals is particularly important as it can be used to probe the magnetism of the d states. Magnetic EXAFS oscillations were detected up to 500 eV above the edge, corresponding to in k-space. Over such a large range, we were able to see long-wavelength wiggles and separate them from Fe nearest-neighbour backscattering and the fast oscillations that had been previously seen. It is shown that without using any deconvolution procedure, a meaningful analysis can be performed despite the interference of the and edges. The experimental data were compared with the results of multiple-scattering calculations, and this enabled us to assign all of the features in both the normal and the magnetic EXAFS Fourier transforms to various single- and multiple-scattering paths. Also, there was found to be less temperature-dependent damping for magnetic EXAFS as than for the normal EXAFS between 75 K and 300 K.

Evidence for photoelectron backscattering by interstitial charge densities

The presence of oscillatory structures in the atomic x-ray absorption background is reported for the first time for surface-EXAFS of cN/Cu(100) and N/Cu(110). Systematic analysis of this feature (AXAFS) and comparison to theory yields new information on the electronic structure of the adsorbate - substrate surface bond. Also, angle and temperature dependent analysis of the AXAFS peak provides qualitative information about interstitial charge density distribution.

Element-specific Curie temperatures of Ni/Cu/Co trilayers

Abstract In order to improve our understanding of the magnetism of 3d-multilayers the following questions are of interest: How does a nonmagnetic cap or spacer layer, like Cu, influence the magnetism of 3d ferromagnetic films? How does the ferromagnetic order of one layer (i.e. Ni) influence another (i.e. Co) via a spacer? Using magnetic circular X-ray dichroism, Co/Ni, Cu/Co and Cu/Ni bilayers and Co/Cu/Ni and Ni/Cu/Co trilayers grown on a Cu(0 0 1) substrate were investigated. After having been covered by 2–7 ML Cu, Ni and Co films exhibit a significantly lower T c . For trilayers different Curie temperatures were determined for Ni and Co when separated by a 2–6 ML Cu spacer. The coupling of Ni and Co layers was found to be both ferromagnetic and antiferromagnetic, depending on the spacer thickness and the sequence of the layers.

Magnetic extended x-ray absorption fine structure at the L3,2 edges of Fe and Co on Cu(001)

We report magnetic extended x-ray absorption fine structure (EXAFS) measurements on 30 monolayer Fe and Co films on Cu(001) substrates at L3,2 edges. For 3d transition metals, the magnetic EXAFS at the L edges is of great interest since it probes final d states which mainly contribute to magnetism. Magnetic EXAFS oscillations were detected up to 500 eV above the edge corresponding to 11.5 A−1 in k space. Over such a large range, the long wavelength wiggles from the Fe and Co nearest neighbor backscattering and previously observed fast oscillations are clearly seen. It is shown that without using any deconvolution procedure a meaningful analysis can be performed despite an interference of L3 and L2 edges. In the case of Fe, experimental data are compared with multiple-scattering calculations.

Surface EXAFS study of the p4g(2 x 2) reconstruction of C on Ni(100)and C on Ni films

We report temperature- and angular-dependent surface extended X-ray absorption fine structure spectroscopy (SEXAFS) measurements of the p4g(2 x 2)C/Ni(100) system. Both a Ni(100) single crystal and ...