Vadim Dyadkin

A new multipurpose diffractometer PILATUS@SNBL.

The diffraction beamline BM01A at the European Synchrotron Radiation Facility (CRG Swiss-Norwegian beamlines) has been successfully operational for 20 years. Recently, a new multifunctional diffractometer based on the Dectris Pilatus 2M detector has been constructed, commissioned and offered to users. The diffractometer combines a fast and low-noise area detector, which can be tilted and moved horizontally and vertically, together with flexible goniometry for sample positioning and orientation. The diffractometer is controlled by a user-friendly and GUI-based software Pylatus which is also used to control various auxiliary equipment. The latter includes several heating and cooling devices, in situ cells and complimentary spectroscopic tools.

A Composite of Complex and Chemical Hydrides Yields the First Al‐Based Amidoborane with Improved Hydrogen Storage Properties

The first Al-based amidoborane Na[Al(NH2 BH3 )4 ] was obtained through a mechanochemical treatment of the NaAlH4 -4 AB (AB=NH3 BH3 ) composite releasing 4.5 wt % of pure hydrogen. The same amidoborane was also produced upon heating the composite at 70 °C. The crystal structure of Na[Al(NH2 BH3 )4 ], elucidated from synchrotron X-ray powder diffraction and confirmed by DFT calculations, contains the previously unknown tetrahedral ion [Al(NH2 BH3 )4 ](-) , with every NH2 BH3 (-) ligand coordinated to aluminum through nitrogen atoms. Combination of complex and chemical hydrides in the same compound was possible due to both the lower stability of the AlH bonds compared to the BH ones in borohydride, and due to the strong Lewis acidity of Al(3+) . According to the thermogravimetric analysis-differential scanning calorimetry-mass spectrometry (TGA-DSC-MS) studies, Na[Al(NH2 BH3 )4 ] releases in two steps 9 wt % of pure hydrogen. As a result of this decomposition, which was also supported by volumetric studies, the formation of NaBH4 and amorphous product(s) of the surmised composition AlN4 B3 H(0-3.6) were observed. Furthermore, volumetric experiments have also shown that the final residue can reversibly absorb about 27 % of the released hydrogen at 250 °C and p(H2 )=150 bar. Hydrogen re-absorption does not regenerate neither Na[Al(NH2 BH3 )4 ] nor starting materials, NaAlH4 and AB, but rather occurs within amorphous product(s). Detailed studies of the latter one(s) can open an avenue for a new family of reversible hydrogen storage materials. Finally, the NaAlH4 -4 AB composite might become a starting point towards a new series of aluminum-based tetraamidoboranes with improved hydrogen storage properties such as hydrogen storage density, hydrogen purity, and reversibility.

Chiral criticality in the doped helimagnets Mn1−yFeySi

S. V. Grigoriev, E. V. Moskvin, V. A. Dyadkin, D. Lamago, 3 Th. Wolf, H. Eckerlebe, and S. V. Maleyev Petersburg Nuclear Physics Institute, Gatchina, 188300 Saint-Petersburg, Russia Laboratoire Léon Brillouin, CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France Karlsruher Institut für Technologie, Institut für Festkörperphysik, P.O. box 3640, D-76021 Karlsruhe, Germany Helmholtz Zentrum Geesthacht, 21502 Geesthacht, Germany (ΩDated: January 19, 2013)

A chiral link between structure and magnetism in MnSi

We consider crystal and magnetic chiral structures for MnSi and isostructural metal silicides, where a complete set of structural and magnetic measurements allows us to define both magnetic and structural chiral configurations. We show that magnetic symmetry inherits chirality from the crystal structure. We derive, with emphasis on symmetry arguments, a new type of magneto-structural relation, namely a symmetrized coupling between structural and magnetic chiralities that provides a structural control on the magnetic chirality.

In situ cell for X-ray single-crystal diffraction experiment at electric field

A special cell for single crystal diffraction experiments under applied electric field has been developed and tested. A wide angle scan range provided by the cell allows the data collection in a large volume of the reciprocal space. Test experiments at synchrotron source for ferroelectric and relaxor single crystals show the possibility to the dependence of both Bragg and diffuse scattering on applied electric field. Further development of insitu diffraction methods with the proposed cell at synchrotronbased and laboratory instruments is discussed.

Controlling the Dzyaloshinskii-Moriya interaction to alter the chiral link between structure and magnetism forFe1−xCoxSi

Monosilicides of 3d-metals frequently show a chiral magnetic ordering with the absolute configuration defined by the chirality of the crystal structure and the sign of the Dzyaloshinskii-Moriya interaction (DMI). Structural and magnetic chiralities are probed here for Fe

Diffuse scattering in lead-based relaxors: synchrotron experiments, data, and models

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High-pressure synthesis of skiagite-majorite garnet and investigation of its crystal structure

Co

Crystal structure and thermal expansion of Mn1−xFexGe

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Thermal expansion of monogermanides of 3d-metals

Si series and their mutual relationship is found to be dependent on the chemical composition. The chirality of crystal structure was previously shown to be governed by crystal growth, and the value of the DMI is nearly the same for all monosilicides of Fe, Co and Mn. Our findings indicate that the sign of the DMI in Fe