Page 17 - ILL Annual Report 2019

SCIENTIFIC HIGHLIGHTS
14-15
COLLEGE 5B – MAGNETIC STRUCTURES
A. Velamazan (College 5B secretary) and T. Saerbeck (focus group secretary)
College 5B is dedicated to the investigation of magnetic structures by means of powder or single-crystal diffraction, small-angle neutron scattering (SANS) and reflectometry. These include polarised neutron techniques that regularly produce results, as can be seen yet again in this year’s Highlights. Frustrated magnets (including pyrochlores), triangular lattices and quantum-spin liquids continue to attract strong interest, while studies on low-dimensional magnetism have been gaining momentum recently. Multiferroic materials
also remain among the most popular subjects. Other frequently investigated topics include superconductors, topological materials (Weyl semi-metals), intermetallics, spin-orbit coupled materials, multipolar orders and molecular magnets.
Both SANS and reflectometry feature strongly in the above-mentioned materials investigations. The main interest of the SANS community continues to be the study of skyrmion-hosting materials, although other topics include superconductivity and magnetic nanoparticles. Reflectometry studies investigate the magnetic properties of materials in the form of thin films and heterostructures, with a significant number of proposals looking at proximity effects at multiferroic oxide interfaces.
COLLEGE 6 – STRUCTURE AND DYNAMICS OF DISORDERED SYSTEMS
M.M. Koza (College 6 secretary)
In recent years, the request for beamtime in College 6 has resembled a rollercoaster ride. Subcommittee meeting after subcommittee meeting, low demand has alternated with all-time highs. The year 2019 was no exception to this persistent cycle. Of no exception either, was the very high quality of the proposed studies. A steadily increasing number of proposals demanding high pressures, polarisation capabilities, magnetic fields, multiple instruments and protocols with the simultaneous application of complementary techniques serves to underscore this point.
In addition, the scientific focus has shifted further, onto complex matter and materials. Interest in the structure and dynamics of molecular liquids, liquid alloys, molten salts, and confined and porous systems outranked attention directed at monatomic samples and glassy and amorphous compounds.
The growing technical and scientific complexity of the studies being proposed is nicely represented by the highlight of the autumn proposal round: a study seeking to understand the effect of high magnetic fields on the dynamic properties of magnetic ionic liquids—made possible by the recent implementation of a high-field magnet at IN5.
COLLEGE 7 – SPECTROSCOPY IN SOLID STATE
PHYSICS AND CHEMISTRY
T. Weber (College 7 secretary)
College 7 deals with non-magnetic spectroscopy in solid-state systems, covering a broad range of topics that includes the determination of phonon dispersion relations and densities of states, phonon-softening effects due to anharmonic interactions, and structural and orbital-ordering phase transitions. Further topics include ionic relaxation and diffusion, as well as the dynamics of molecular and physio-/chemisorbed systems.
While College 7 has a wide variety of cold- and thermal-neutron spectrometers and diffractometers at its disposal, in the recent proposal
round most days of beamtime were awarded for experiments at
the high-flux, thermal-neutron, three-axis spectrometer IN8, the time-of-flight spectrometers IN6-SHARP and IN5, the high-resolution spin-echo instrument IN11 and the IN1-LAGRANGE spectrometer. The complexity of both the investigated systems and the instrumental resolution functions typically require sophisticated theoretical models and data analysis tools. Assistance in these fields can be provided by the ILL’s Theory and Scientific Computing groups.
COLLEGE 8 – STRUCTURE AND DYNAMICS OF BIOLOGICAL SYSTEMS
N. Coquelle (College 8 secretary)
College 8 focuses on biological molecules, using a large palette of techniques and instruments to unravel molecular structures and link these to their functions and/or dynamics. Neutron crystallography (D19, LADI and soon DALI) provides a technique for visualising hydrogen/deuterium protein atoms and understanding their catalytic mechanism or their mode of recognising small molecules. Studies in solutions are performed using our unique set of SANS machines (D11, D22 and D33). Signals from a molecular type (DNA vs protein or lipids vs protein for example) can be masked out using deuteration.
Reflectometers (Figaro, D17) and the diffractometer D16 are excellent instruments for studying the properties of bio-mimicking surfaces (model lipidic bilayers) and the mode of interaction or the type of modification triggered by specific macromolecules on these lipidic surfaces. Finally, the neutron spectrometers IN15, IN13 and IN11 are used to gain insight into the dynamics of these biological systems over a large range of time and q.
There are several laboratories available on the EPN campus to facilitate sample preparation, including the D-lab for the perdeuteration of biological molecules and the EMBL biology laboratories for specific operations. The PSB platform and the PSCM offer a large variety of complementary techniques to further characterise samples.
COLLEGE 9 – SOFT CONDENSED MATTER
S. Prevost (College 9 secretary) and A. Maestro (focus group secretary) College 9 covers the vast field of soft condensed matter, studying the
architecture of complex fluids at the nano- to micrometre scales, its evolution with time-resolved experiments under various stresses, and the related dynamics. Over the last few proposal rounds we have observed growing demand for interfacial studies.
Our users benefit from the support of the PSCM for complementary measurements. Additionally, the SMSS offers an increasing number of techniques and sample environments that can be used both ex situ and in situ, such as the DLS currently commissioned for SANS, the automatic suite for adsorption and Langmuir troughs which increase performance and turnover in reflectometry, and the combined humidity, pH and pressure cell for both SANS and NR.
Many LSS instruments will benefit from the on-going Endurance Phase 2 programme, which will bring about the renewal of H15 including a full upgrade of D11 and new detectors for D11 and D22; as well
as the D50/NeXt overhaul, which will bring imaging capabilities
to the ILL, boosting the opportunities for College 9’s users. The TOF instruments are more and more in demand from College 9 proposers, reflecting the importance of dynamics in relation to structure in colloids.
More information on the support facilities cited can be found on p.106.
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