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Instruments / Technical Area	Publication Details	Published
I11-High Resolution Powder Diffraction	Layered CeSO and LiCeSo oxide chalcogenides obtained via topotactic oxidative and reductive transformations Simon J. Cassidy , Michael J. Pitcher , Jared J. K. Lim , Joke Hadermann , Jeremy P. Allen , Graeme W. Watson , Sylvia Britto , Elena J. Chong , David G. Free , Clare P. Grey , Simon J. Clarke Inorganic Chemistry 58, 3838–3850 DOI: 10.1021/acs.inorgchem.8b03485 Diamond Proposal Number(s): [13284, 18786] Open Access Show Abstract ▼ Abstract: The chemical accessibility of the CeIV oxidation state enables redox chemistry to be performed on the naturally coinage-metal-deficient phases CeM1–xSO (M = Cu, Ag). A metastable black compound with the PbFCl structure type (space group P4/nmm: a = 3.8396(1) Å, c = 6.607(4) Å, V = 97.40(6) Å3) and a composition approaching CeSO is obtained by deintercalation of Ag from CeAg0.8SO. High-resolution transmission electron microscopy reveals the presence of large defect-free regions in CeSO, but stacking faults are also evident which can be incorporated into a quantitative model to account for the severe peak anisotropy evident in all the high-resolution X-ray and neutron diffractograms of bulk CeSO samples; these suggest that a few percent of residual Ag remains. A straw-colored compound with the filled PbFCl (i.e., ZrSiCuAs- or HfCuSi2-type) structure (space group P4/nmm: a = 3.98171(1) Å, c = 8.70913(5) Å, V = 138.075(1) Å3) and a composition close to LiCeSO, but with small amounts of residual Ag, is obtained by direct reductive lithiation of CeAg0.8SO or by insertion of Li into CeSO using chemical or electrochemical means. Computation of the band structure of pure, stoichiometric CeSO predicts it to be a Ce4+ compound with the 4f-states lying approximately 1 eV above the sulfide-dominated valence band maximum. Accordingly, the effective magnetic moment per Ce ion measured in the CeSO samples is much reduced from the value found for the Ce3+-containing LiCeSO, and the residual paramagnetism corresponds to the Ce3+ ions remaining due to the presence of residual Ag, which presumably reflects the difficulty of stabilizing Ce4+ in the presence of sulfide (S2–). Comparison of the behavior of CeCu0.8SO with that of CeAg0.8SO reveals much slower reaction kinetics associated with the Cu1–xS layers, and this enables intermediate CeCu1–xLixSO phases to be isolated.	Feb 2019
B18-Core EXAFS I19-Small Molecule Single Crystal Diffraction	Soft chemical control of the crystal and magnetic structure of a layered mixed valent manganite oxide sulfide Jack Blandy , Artem M. Abakumov , Kirsten Christensen , Joke Hadermann , Paul Adamson , Simon Cassidy , Silvia Ramos , David Free , Harry Cohen , Daniel Woodruff , Amber Thompson , Simon J Clarke Apl Materials 3 (4) DOI: 10.1063/1.4918973 Open Access Show Abstract ▼ Abstract: Oxidative deintercalation of copper ions from the sulfide layers of the layered mixed-valent manganite oxide sulfide Sr2MnO2 Cu 1.5S2 results in control of the copper-vacancy modulated superstructure and the ordered arrangement of magnetic moments carried by the manganese ions. This soft chemistry enables control of the structures and properties of these complex materials which complement mixed-valent perovskite and perovskite-related transition metal oxides.	Apr 2015
B18-Core EXAFS	Control of the superconducting properties of Sr2−xCaxVO3FeAs through isovalent substitution Alex Corkett , David Free , Simon Cassidy , Silvia Ramos , Simon J. Clarke Journal Of Solid State Chemistry 216, 91 - 98 DOI: 10.1016/j.jssc.2014.02.024 Show Abstract ▼ Abstract: The effect of the isovalent substitution of Sr2+ by Ca2+ on the structure and superconducting properties of Sr2?xCaxVO3FeAs is described in the compositional range 0?x?0.5. SQUID magnetometry measurements reveal that after an initial increase in Tc, which is maximised at 29.5 K in Sr1.95Ca0.05VO3FeAs, a rapid suppression of superconductivity is observed with increasing x. XANES spectra of Sr2?xCaxVO3FeAs collected on the Fe and V absorption K-edges show that the position of both edges are invariant with composition within the experimental uncertainty. A combination of synchrotron X-ray powder diffraction and neutron powder diffraction techniques is used to rationalise the observed changes in Tc with x, in terms of changes to the structure of the FeAs layer upon partial Ca substitution. These findings demonstrate that superconductivity in the Fe-based superconductors is extremely sensitive to the crystal structure with Tc maximised in samples with regular FeAs4-tetrahedra.	Aug 2014

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