THE SWISS - NORWEGIAN BEAM LINES (General description)
Wiki Page SNBL
The mission of the SNBL is to provide scientists from both Norway and Switzerland, from both academia and industry, with increased access to synchrotron radiation. A user on SNBL has access to state-of-the-art, custom-designed instrumentation for diffraction and absorption experiments. Both partner countries have relatively large and exceptionally active scientific communities using X-ray diffraction and absorption as their main probes; for these groups the amount of public beamtime offered by ESRF was insufficient from day one, and this is the raison d’être of the Swiss-Norwegian Beam Lines at ESRF. Nowadays, it is fully understood by the scientific community that many of the most challenging problems in structural crystallography can be solved only with the use of synchrotron radiation, and even then, often enough, only by harnessing the combined power of two or more experimental techniques (such as, e.g., powder and single-crystal diffraction). The SNBL has four such different experimental techniques, which are distributed over two beamlines, and presently include:
High-resolution single-crystal diffractometry
Large-area diffraction imaging
High-resolution powder diffractometry
“SNBL – Planning for the next decade”(program) - Photos by Serge Claisse (ILL)
Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formation
Phase transitions that occur in materials, driven, for instance, by changes in temperature or pressure, can dramatically change the materials’ properties. Discovering new types of transitions and understanding their mechanisms is important not only from a fundamental perspective, but also for practical applications. Here we investigate a recently discovered Fe4O5 that adopts an orthorhombic CaFe3O5-type crystal structure that features linear chains of Fe ions. On cooling below ∼150 K, Fe4O5 undergoes an unusual charge-ordering transition that involves competing dimeric and trimeric ordering within the chains of Fe ions. This transition is concurrent with a significant increase in electrical resistivity. Magnetic-susceptibility measurements and neutron diffraction establish the formation of a collinear antiferromagnetic order above room temperature and a spin canting at 85 K that gives rise to spontaneous magnetization. We discuss possible mechanisms of this transition and compare it with the trimeronic charge ordering observed in magnetite below the Verwey transition temperature.
B,C, Examples of reciprocal lattices of X-ray diffraction intensities at 260 K (B) and 100 K (C). a* and b* are the axes of reciprocal lattices.
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