Commissioning CXI-FTH

First tests of the Fourier Transform Holography set-up on the SEXTANTS beamline started in October 2010, using a temporary endstation (collaboration with J. Lüning, LCP-MR). Samples were Co/Pd multilayers fabricated by R. Delaunay (LCP-MR, Paris VI), using magnetron sputtering. Nanostructuring of the samples was carried out by F. Fortuna (CSNSM, Orsay), using Focused Ion Beam (FIB) etching. FIB is used to define the area to be imaged (1.6μm in our case) and the reference holes for the holography, whose size enter in the definition of the ultimate spatial resolution.

Fig. 1 shows the coherent scattering diagram collected using an in-vacuum CCD. The image size corresponds to 190μm-1 in reciprocal space. Data were collected at the Co-L3 edge energy (780eV), using circularly polarized X-rays. Co/Pd multilayers are homogeneous, apart from their magnetic structure. Worm-like domains with perpendicular up/down magnetization form in the Co layers, originating regular structures with sub-micron period.

Fig. 2 compares the Fourier transform of coherent scattering patterns obtained with opposite helicities of the photons. Both images display light/dark modulations, related to the magnetic structure of the sample. Line profiles show clearly that these modulations are exactly out of phase when the light polarization is inverted, confirming their magnetic origin. Therefore, we can highlight pure magnetic contributions to the coherent scattering by image subtraction, eliminating all other structural or spurious effects.