8 research outputs found
Electronic structure investigation of a charge density wave coupled to a metal-to-metal transition in Ce3Co4Sn13
We study the electronic structure of the skutterudite Ce3Co4Sn13, which is known to exhibit a charge density wave (CDW) transition, at temperature TCDW∼160 K, coupled to a metal-to-metal transition. We use temperature dependent hard x-ray photoemission spectroscopy (HAXPES) and x-ray absorption spectroscopy (XAS) to investigate the occupied and unoccupied electronic states of Ce3Co4Sn13. The Co 2p and Sn 3p core level spectra show small but finite shifts in binding energy positions across TCDW while Ce 3d core level spectra do not show any change across the transition. The Ce M4,5-edge XAS spectrum compared with calculations indicate a typical trivalent ionic Ce3+ spectral shape, ruling out Kondo screening in Ce3Co4Sn13. In contrast, the Co L2,3-edge XAS spectrum compared with a calculated spectrum shows evidence for hybridization with neighboring Sn atoms in a trigonal prismatic co-ordination. Temperature dependent XAS across the Co L2,3-edge shows a small shift across TCDW, consistent with HAXPES results. Detailed XAS measurements as a function of temperature show that the spectral shifts occur with a hysteresis across TCDW, indicative of a first-order transition. Valence band spectra show a normal Fermi edge above and below TCDW. The Co 3d states are observed at a binding energy of ∼2 eV while the Ce 4f states occur as a weak feature within 0.5 eV of the Fermi level. The results suggest an unusual CDW transition coupled to a metal-to-metal transition in Ce3Co4Sn13
Fossil Turtles from the Kiyokawa Formation of the Shimosa Group (Pleistocene) at Chiba Prefecture
Research and Development of 3d Multinary Functional Materials for Substitution of Rare and Toxic Elements
Electronic structure investigation of a charge density wave coupled to a metal-to-metal transition in Ce3Co4Sn13
We study the electronic structure of the skutterudite Ce3Co4Sn13, which is known to exhibit a charge density wave (CDW) transition, at temperature TCDW∼160 K, coupled to a metal-to-metal transition. We use temperature dependent hard x-ray photoemission spectroscopy (HAXPES) and x-ray absorption spectroscopy (XAS) to investigate the occupied and unoccupied electronic states of Ce3Co4Sn13. The Co 2p and Sn 3p core level spectra show small but finite shifts in binding energy positions across TCDW while Ce 3d core level spectra do not show any change across the transition. The Ce M4,5-edge XAS spectrum compared with calculations indicate a typical trivalent ionic Ce3+ spectral shape, ruling out Kondo screening in Ce3Co4Sn13. In contrast, the Co L2,3-edge XAS spectrum compared with a calculated spectrum shows evidence for hybridization with neighboring Sn atoms in a trigonal prismatic co-ordination. Temperature dependent XAS across the Co L2,3-edge shows a small shift across TCDW, consistent with HAXPES results. Detailed XAS measurements as a function of temperature show that the spectral shifts occur with a hysteresis across TCDW, indicative of a first-order transition. Valence band spectra show a normal Fermi edge above and below TCDW. The Co 3d states are observed at a binding energy of ∼2 eV while the Ce 4f states occur as a weak feature within 0.5 eV of the Fermi level. The results suggest an unusual CDW transition coupled to a metal-to-metal transition in Ce3Co4Sn13
Palaeoclimate Status of Marine Isotope Stage (MIS) 7 to Explain Fauna/Flora of the Kiyokawa Formation, Shimosa Group, East-central Japan: Evidence from Pollen and Proxy Records
Political enthusiasm for social pensions and its eventual decline in Taiwan: an institutional account of pension dynamics in a new democracy
Advances in Male Contraception
Despite significant advances in contraceptive options for women over the last 50 yr, world population continues to grow rapidly. Scientists and activists alike point to the devastating environmental impacts that population pressures have caused, including global warming from the developed world and hunger and disease in less developed areas. Moreover, almost half of all pregnancies are still unwanted or unplanned. Clearly, there is a need for expanded, reversible, contraceptive options. Multicultural surveys demonstrate the willingness of men to participate in contraception and their female partners to trust them to do so. Notwithstanding their paucity of options, male methods including vasectomy and condoms account for almost one third of contraceptive use in the United States and other countries. Recent international clinical research efforts have demonstrated high efficacy rates (90–95%) for hormonally based male contraceptives. Current barriers to expanded use include limited delivery methods and perceived regulatory obstacles, which stymie introduction to the marketplace. However, advances in oral and injectable androgen delivery are cause for optimism that these hurdles may be overcome. Nonhormonal methods, such as compounds that target sperm motility, are attractive in their theoretical promise of specificity for the reproductive tract. Gene and protein array technologies continue to identify potential targets for this approach. Such nonhormonal agents will likely reach clinical trials in the near future. Great strides have been made in understanding male reproductive physiology; the combined efforts of scientists, clinicians, industry and governmental funding agencies could make an effective, reversible, male contraceptive an option for family planning over the next decade