We report on single-pulse resonant magnetic scattering experiments using soft x-ray pulses generated by the free-electron laser FLASH at DESY. We could record a magnetic diffraction pattern from a Co/Pt multilayer sample at the Co M 2,3 edge with a single 30-fs-long FEL pulse. The analysis of the magnetic small-angle scattering signal for subsequent pulses indicates a threshold energy density below which there is no indication that the magnetic properties of the sample might be altered.
Coherent diffractive imaging for the reconstruction of a two-dimensional (2D) finite crystal structure with a single pulse train of free-electron laser radiation at 7.97 nm wavelength is demonstrated. This measurement shows an advance on traditional coherent imaging techniques by applying it to a periodic structure. It is also significant that this approach paves the way for the imaging of the class of specimens which readily form 2D, but not three-dimensional crystals. We show that the structure is reconstructed to the detected resolution, given an adequate signal-to-noise ratio.
We report on Fourier transform holography (FTH) experiments on nanostructured Co/Pt multilayer films with 40 nm spatial imaging resolution. The films have been nanostructured by means of focused ion beam (FIB) milling. Applying the ion beam through the supporting membrane with controlled and homogeneous dosing allows for higher resolution magnetic structuring of the ion-sensitive film compared to direct FIB patterning. Nanostructured samples with magnetic stripes exposed to different ion doses and magnetic arrays with 200 nm lattice constant were successfully prepared and imaged by FTH. We present image-processing routines for artifact-free image reconstruction. With this, we could investigate the FIB-induced anisotropy modulation and the perpendicular domain structure in the nanostructured samples, showing how to control the domain size and configuration by applying the appropriate ion dose either homogeneously or concentrated in single spots.
We present a new x-ray microscopy technique based on Fourier transform holography FTH, where the sample is separate from the optics part of the setup. The sample can be shifted with respect to the holography optics, thus large-scale or randomly distributed objects become accessible. As this extends FTH into a true microscopy technique, we call it x-ray holographic microscopy XHM. FTH allows nanoscale imaging without the need for nanometer-size beams. Simple Fourier transform yields an unambiguous image reconstruction. We demonstrate XHM by studying the magnetic domain evolution of a Co/Pt multilayer film as function of locally varied iron overlayer thickness.
We report on a resonant magnetic scattering experiment using soft x-ray pulses generated from a freeelectron laser ͑FEL͒. The free-electron laser was operated at a fundamental wavelength of 7.97 nm and radiation at the fifth harmonic originating from self-amplified stimulated emission at 1.59 nm with an average energy of 4 nJ per pulse was detected. We demonstrate the feasibility of resonant magnetic scattering at FEL sources by using a Co/Pd multilayer as prototype sample that was illuminated with 20-fs-long soft x-ray pulses tuned to the Co L 3 absorption edge at 778.1 eV ͑1.59 nm͒.
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