Sub-100 nanometer lensless probing of Co/Pd magnetic nanodomains using a table-top femtosecond soft X-ray harmonic source

Abstract : We present recent developments of our table-top femtosecond high flux harmonic beamline towards single-shot probing of magnetic nanostructures. High harmonic generation (HHG) optimization in a single and two-color infrared laser pulse mode was investigated at high laser energy. Up to 10(9) photons per harmonic are generated between 40 and 80 eV in a single femtosecond laser shot. These soft X-ray harmonic photons are employed to characterize at the nanoscale the magnetic network of Co/Pd multilayer samples using resonant small-angle X-ray scattering. Selecting harmonics in the vicinity of magnetically dichroic absorption resonances of cobalt and palladium (Co M-2,M-3 at 60eV and Pd N-2,N-3 at 51eV) gives access to the magnetic nanodomain spatial structure. The magnetic scattering efficiency at the Pd edge is found to be comparable to that at the Co edge. This indicates that the Pd layers exhibit a significant induced magnetic moment. Magnetic sample optimization is then performed by characterizing its scattering efficiency as a function of layer composition and number of repetitions. We finally measure the spatial organization of magnetic nanodomains with a sub-100nm spatial resolution from a single femtosecond X-ray pulse.