Soft x-ray coherent magnetic scattering experiments

The increased coherence of third generation synchrotron sources allows us to port laser techniques such as holography and dynamical light scattering from the visible to the x-ray spectral range. In addition to the obvious improvement in resolution, the x-ray range may allow for new variants that are not possible in the visible, as exemplified by techniques that use the strong magnetic contrast at soft x-ray resonances. In this talk I will report on soft x-ray coherent magnetic scattering experiments performed on stripe magnetic domain systems as occurring in amorphous GdFe thin films with perpendicular anisotropy. This system was chosen in order to have maximum magnetic contrast, negligible charge scattering and minor multiple scattering. These experiments were performed at the ESRF on a spectroscopy beam line using a phosphor screen + visible CCD detector. A careful Kramers Kronig analysis of the magnetic cross section was made at both the Gd M5 and the Fe L3 resonances, which matches experimentally observed scattering cross sections remarkably well and is in agreement with atomic calculations. Despite non-ideal conditions we were able to obtain very high resolution speckle patterns both of ordered and disordered stripe systems from which the local magnetic correlation function can be obtained straightforwardly. Attempts at speckle inversion of these data have been foiled by lack of qrange. 10 μm beam G d M 5 resonance 40 nm G dFe 180 nm period (M FM )