Interlayer magnetic coupling for Fe/Si multilayers

The antiferromagnetic (AFM) interlayer exchange coupling for sputtered Fe/Si multilayers have been studied by magnetometry, wide-angle neutron diffraction, and spin-polarized neutron reflectometry. Ferromagnetic resonance and Raman scattering measurements have been applied for the characterization of the multilayers. To look for a possible modification of exchange coupling when Si is replaced by Ge, similar Fe/Ge multilayers have been prepared by the same technique. No AFM coupling has been found for Fe/Ge system. Present results differ in part from the literature data and suggest an influence of the sample preparation on the details of its magnetic properties

Experimental set-up and procedures for the investigation of XUV free electron laser interactions with solids

In this article, we describe the experimental station and procedures for investigating the interaction of short-wavelength free-electron lasers (FELs) pulses with solids. With the advent of these sources, a unique combination of radiation properties (including wavelength range from tens of nanometers down to sub-Angstroms, femtosecond pulse duration, and high pulse energy reaching milli-Joules level) creates new research possibilities for the systematic studies of radiation-induced structural changes in solids. However, the properties of the intense FEL radiation generate, apart from the new experimental opportunities, extreme demands on the experimental set-up (mostly in terms of radiation hardness of detectors and their saturation levels). Thus, radiation-induced phase transitions in solids, beyond the fundamental scientific interest, are of importance for the design of FEL beamlines and instruments which interact with the direct beam. In this report, we focus on the instrumentation and experimental techniques used in the recent studies performed at the FLASH facility in Hamburg

Damage studies of multilayer optics for XUV free electron lasers

We exposed standard Mo/Si multilayer coatings, optimized for 13.5 nm radiation to the intense femtosecond XUV radiation at the FLASH free electron laser facility at intensities below and above the multilayer ablation threshold. The interaction process was studied in-situ with reflectometry and time resolved optical microscopy, and ex-situ with optical microscopy (Nomarski), atomic force microscopy and high resolution transmission electron microscopy. From analysis of the size of the observed craters as a function of the pulse energy the threshold for irreversible damage of the multilayer could be determined to be 45 mJ/cm2. The damage occurs on a longer time scale than the XUV pulse and even above the damage threshold XUV reflectance has been observed showing no measurable loss up to a power density of 1013 W/cm2. A first explanation of the physics mechanism leading to damage is given