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Author: Liu, X. × Publisher: London : Nature Publishing Group ×

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    Spin-orbit-driven magnetic structure and excitation in the 5d pyrochlore Cd2Os2O7
    (London : Nature Publishing Group, 2016) Calder, S.; Vale, J.G.; Bogdanov, N.A.; Liu, X.; Donnerer, C.; Upton, M.H.; Casa, D.; Said, A.H.; Lumsden, M.D.; Zhao, Z.; Yan, J.-Q.; Mandrus, D.; Nishimoto, S.; van den Brink, J.; Hill, J.P.; McMorrow, D.F.; Christianson, A.D.
    Much consideration has been given to the role of spin-orbit coupling (SOC) in 5d oxides, particularly on the formation of novel electronic states and manifested metal-insulator transitions (MITs). SOC plays a dominant role in 5d5 iridates (Ir4þ), undergoing MITs both concurrent (pyrochlores) and separated (perovskites) from the onset of magnetic order. However, the role of SOC for other 5d configurations is less clear. For example, 5d3 (Os5þ) systems are expected to have an orbital singlet with reduced effective SOC. The pyrochlore Cd2Os2O7 nonetheless exhibits a MIT entwined with magnetic order phenomenologically similar to pyrochlore iridates. Here, we resolve the magnetic structure in Cd2Os2O7 with neutron diffraction and then via resonant inelastic X-ray scattering determine the salient electronic and magnetic energy scales controlling the MIT. In particular, SOC plays a subtle role in creating the electronic ground state but drives the magnetic order and emergence of a multiple spin-flip magnetic excitation.
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    Free-standing Fe2O3 nanomembranes enabling ultra-long cycling life and high rate capability for Li-ion batteries
    (London : Nature Publishing Group, 2014) Liu, X.; Si, W.; Zhang, J.; Sun, X.; Deng, J.; Baunack, S.; Oswald, S.; Liu, L.; Yan, C.; Schmidt, O.G.
    With Fe2O3 as a proof-of-concept, free-standing nanomembrane structure is demonstrated to be highly advantageous to improve the performance of Li-ion batteries. The Fe2O3 nanomembrane electrodes exhibit ultra-long cycling life at high current rates with satisfactory capacity (808 mAh g-1 after 1000 cycles at 2 C and 530 mAh g-1 after 3000 cycles at 6 C) as well as repeatable high rate capability up to 50 C. The excellent performance benefits particularly from the unique structural advantages of the nanomembranes. The mechanical feature can buffer the strain of lithiation/delithiation to postpone the pulverization. The two-dimensional transport pathways in between the nanomembranes can promote the pseudo-capacitive type storage. The parallel-laid nanomembranes, which are coated by polymeric gel-like film and SEI layer with the electrolyte in between layers, electrochemically behave like numerous "mini-capacitors" to provide the pseudo-capacitance thus maintain the capacity at high rate.