The orientation of magnetic moments at the (100) surface of antiferromagnetic NiO single crystals is studied by x-ray linear magnetic dichroism in photoemission microscopy. T domains are observed terminating at the surface, with domain boundaries running mostly along in-plane [10] directions. From the detailed polarization dependence we find that the magnetic surface structure of a cleaved crystal is bulk terminated. This is in contrast to sputtered surfaces, where magnetic moments lie within the surface plane, forming a magnetically relaxed structure. These findings are of importance for understanding the exchange bias phenomenon.
A novel instrument for imaging ESCA is described. It is based on a tandem arrangement of two
hemispherical energy analysers used as an imaging energy filter. The main spherical aberration
(α2-term) of the analyser is corrected by the antisymmetry of the tandem configuration. The
kinetic energy range useable for imaging extends up to 1.6 keV; this is compatible with Mg and
Al Kα
laboratory x-ray sources. First experiments on the chemical surface composition of a
Cu0.98Bi0.02
polycrystal, a GaAs/AlGaAs heterostructure and Ag crystallites on Si(111) have been
performed using synchrotron radiation. The results reveal an energy resolution of
190 meV and a lateral resolution (edge resolution) of 120 nm. Besides elimination
of the analyser’s spherical aberration, the tandem arrangement largely retains
the time structure of the electron signal, unlike a single hemispherical analyser.
We report high-resolution observations of antiferromagnetic (AF) domain walls at the surface of NiO and determine the typical width of AF walls in this material to be of the order of 150 nm. We observe a number of different types of domain walls, including double walls caused by long-range interaction between walls. We describe the observed wall profiles by a model containing the exchange interaction and magnetostriction as basic ingredients. The good agreement of this model with experiment shows that the formation of walls between antiferromagnetic domains in NiO and their properties are dominated by magnetoelastic interactions.
Modular plants using intensified continuous processes represent an appealing concept for the production of pharmaceuticals. It can improve quality, safety, sustainability, and profitability compared to batch processes; besides, it enables plug-and-produce reconfiguration for fast product changes. To facilitate this flexibility by real-time quality control, we developed a solution that can be adapted quickly to new processes and is based on a compact nuclear magnetic resonance (NMR) spectrometer. The NMR sensor is a benchtop device enhanced to the requirements of automated chemical production including robust evaluation of sensor data. Beyond monitoring the product quality, online NMR data was used in a new iterative optimization approach to maximize the plant profit and served as a reliable reference for the calibration of a near-infrared (NIR) spectrometer. The overall approach was demonstrated on a commercial-scale pilot plant using a metal-organic reaction with pharmaceutical relevance.
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