GenX 3: the latest generation of an established tool.

Since its publication more than 15 years ago the GenX software has been continuously developed and has established itself as a standard package for analyzing X-ray and neutron reflectometry data. The evolution of the software during the last two major revisions is reported here. This includes a simplified model builder for beginners, simple samples, additional sample models, statistical error analysis and the use of just-in-time compilation modules for the reflectometry kernel to achieve higher performance. In addition, the influence of experimental errors on the reflectivity curve is discussed, and new features are described that allow the user to include these in the error statistics to improve the fitting and uncertainty estimation.

Bandwidth and stability of the stochastic parallel gradient descent algorithm for phase control in coherent beam combination.

The bandwidth and stability limits of the stochastic parallel gradient descent (SPGD) algorithm used for coherent beam combination is investigated by deriving an analytical model for the phase control loop. The analytical model is compared to experiments and numerical simulations using a laboratory tiled coherent beam combination setup. The setup consisted of four sub-beams from fiber-optic collimators and used a backreflected signal as feedback. A rotating phase plate was used to induce phase disturbances into the system. The analytical model compared favorably to numerical simulations and experiments as well as to other studies found in the literature. The results can be used to provide an estimate of the achievable phase control bandwidth of coherent beam combination systems using SPGD as a control algorithm.

Perpendicular magnetocrystalline anisotropy in tetragonally distorted Fe-Co alloys.

We report on the experimental realization of tetragonal Fe-Co alloys as a constituent of Fe0.36Co0.64/Pt superlattices with huge perpendicular magnetocrystalline anisotropy energy, reaching 210 microeV/atom, and a saturation magnetization of 2.5 microB/atom at 40 K, in qualitative agreement with theoretical predictions. At room temperature the corresponding values and are achieved. This suggests that Fe-Co alloys with carefully chosen combinations of composition and distortion are good candidates for high-density perpendicular storage materials.