91 research outputs found
Supporting Information for Topochemical Synthesis and Electronic Structure of High-Crystallinity Infinite-Layer Nickelates on an Orthorhombic Substrate
No full textAdditional materials and methods, experimental details of the thin-film growth and reduction processes and characterization methods, and experimental and calculation data, including growth of precursor films; reduction processes; X-ray diffraction and atomic force microscopy; scanning transmission electron microscopy; transport measurements; X-ray absorption spectroscopy and resonant inelastic X-ray scattering; density functional theory calculations; lattice parameters of infinite layer nickelate determined using STEM; visualization of oxygen atoms using annular bright field imaging; the strain distribution of infinite layer nickelate; XRD pattern of the reduction process using CaH2 and NaH; ABF-STEM image of the NdNiO3 film and the NdNiO2 film; the enlarged HADDF-STEM image and strain distribution of the interface region; magnetoresistance of representative samples; DFT calculated band structure; the experimental geometry of XAS and RIXS measurements; XRD data, fitting thickness, and resistivity of various NNO2 samplesPeer reviewe
The role of boron lattice expansion in superconducting diborides
No full textLattice structure of the diborides has been studied to explore a possible relation between high Tc superconductivity and expansion of the boron plane. High purity Mg1-xAxB2 diborides have been prepared by direct reaction of the elements and the lattice parameters are determined by X-ray diffraction, providing a measure to the strain ε of the B-B distance. The results show that the superconductivity in these intermetallics appears in a critical region of tensile strain and charge density in the boron plane. © 2003 Elsevier Ltd. All rights reserved
Temperature dependent local Cu-O displacements from underdoped to overdoped La-Sr-Cu-O superconductor
No full textWe have studied doping evolution of the temperature dependent local Cu-O displacements in the La(2-x)Sr(x)CuO(4) superconductor by polarized Cu K-edge extended X-ray absorption fine structure (EXAFS) measurements. While temperature dependent Debye-Waller factor of the Cu-O bonds, measuring the local Cu-O displacements, shows an anomalous increase at low temperature for the underdoped single crystals, we do not find such a dependence for the case of the overdoped system. The results, which are discussed in the light of recent angle resolved photoemission measurements, provide an evidence for some important correlation between the doping dependent electron-lattice interaction, the charge inhomogeneities and the local Cu-O displacements in the copper oxide superconductors
RuK-edge absorption study on the La1-xCexRu2 system
No full textWe have measured high-resolution Ru K-edge x-ray absorption spectra for the intermetallic La1-xCexRu2 system. Multiple-scattering calculations are made to explore the origins of different features observed in the experimental x-ray absorption near-edge structure (XANES) and their variation with Ce doping. The experiments and theoretical analysis demonstrate that the Ce doping in La1-xCexRu2 has a direct influence on the states at the Fermi level and hence the hybridization between the f and d states induced by doping
Exchange interactions in Ca3Co2O6 probed locally by NMR
No full textWe have measured the nuclear spin-lattice relaxation of 59Co in the geometrically frustrated Ising-type spin-chain system Ca3Co2O6 as a function of temperature and applied magnetic field. In the nearly-saturated ferrimagnetic and ferromagnetic regimes considered here, the field-dependent energy scales governing the spin-lattice relaxation rates reflect the energy cost of a spin flip in the Co ions adjacent to the probed nuclei. This results in a thermally activated form for the nuclear relaxation rates, which can be exploited as a local probe of the exchange interactions. In particular, the measurements enable the values of intra- and interchain exchange constants J1, J2+J3 to be directly extracted from the data. By using a quasi-one-dimensional model, we then determine the value of J2 consistent with the spin-density-wave order observed in zero field
Experimental evidence of chemical-pressure–controlled superconductivity in cuprates
No full textX-ray absorption spectroscopy (XAS) and high-resolution X-ray diffraction are combined to study the interplay between electronic and lattice structures in controlling the super- conductivity in cuprates with a model charge-compensated CaxLa1−xBa1.75−xLa0.25+xCu3Oy (0 x < 0.5, y ≈ 7.13) system. In spite of a large change in Tc, the doped holes, determined by the Cu L and O K XAS, hardly show any variation with the x. On the other hand, the CuO2 plaquette size shows a systematic change due to different size of substituted cations. The results provide a direct evidence for the chemical pressure being a key parameter for controlling the superconducting ground state of the cuprates
NMR study of magnetic order, metamagnetic transitions, and low-temperature spin freezing in Ca_{3}Co_{2}O_{6}
No full textWe report on a (59)Co NMR investigation of the trigonal cobaltate Ca(3)Co(2)O(6) carried out on a single crystal, providing precise determinations of the electric field gradient and chemical shift tensors, and of the internal magnetic fields at the nonmagnetic Co I sites, unavailable from former studies on powders. The magnetic-field-induced ferri-and ferromagnetic phases at intermediate temperature (e.g., 10 K) are identified by distinct internal fields, well accounted for by purely dipolar interactions. The vanishing transferred hyperfine field at the Co I site indicates that the Co(3+) (I) orbitals do not participate in the intrachain superexchange, in disagreement with a previous theoretical model. The strong Ising character of the system is confirmed experimentally by the field dependence of the resonance lines, indicating that local moments are saturated even at the phase boundaries. In the vicinity of the critical fields, nuclear spin-spin relaxations detect the spin-reversal dynamics of large magnetic assemblies, either Ising chain fragments or finite-size domains, which drive the metamagnetic transitions. Such collective excitations exhibit a glassy behavior, slowing down to subacoustic frequencies and freezing at low temperature. The relevance of such slow-fluctuation modes for the low-temperature multistep behavior reported in the magnetization is discussed
Valence State of Pb in Transition Metal Perovskites PbTMO3 (TM= Ti, Ni) Determined From X-Ray Absorption Near-Edge Spectroscopy
No full textWe present a combined experimental and theoretical Pb‐L3 X‐ray absorption near‐edge spectroscopy (XANES) to investigate the chemical state of Pb in transition metal perovskites PbTMO3 (TM= Ti, Ni). A pre‐edge feature originated from the excitation of a 2p core electron to the 6s orbital is only observed in PbNiO3, from which the valence of Pb is determined to be Pb4+ with two 6s holes. However, no such 2p–6s related excitation was observed in PbTiO3, indicating the formation of Pb2+ with fully occupied 6s2 state in this materials. Our results demonstrate that this pre‐edge peak from dipole allowed 2p–6s transition is a sensitive finger‐print of the Pb valence state in solid state materials
Endoscopic removal of supernumerary tooth from the nasal cavity of a child: a case report
No full textIntroduction: A case report showing the removal of a supernumerary tooth from the nasal cavity by means of an endoscopic approach is presented.
Materials and methods: A 9-year-old healthy child presented to our department because of the right central incisor which appeared clinically rotated. The observation of orthopantomography revealed the presence of a supernumerary tooth in the anterior maxilla with the crown positioned towards the nasal floor. The maxillary CT demonstrated a quite close relationship of the tooth with the nasal cavity, so a nasal approach was planned.
Results: Under general anesthesia the supernumerary tooth was removed by means of an endoscopic approach from a nostril. During the extraction the adjacent structures were unharmed. The postoperative course was uneventful.
Conclusions: This case report suggests that in case of supernumerary teeth positioned close to the nasal cavity, trans-nasal endoscopy may represent a valid alternative to more demolishing traditional surgery
Evidence for Local Lattice fluctuations as a response function of the charge stripe order in the La1.48Nd0.4Sr0.12Cu04 system
No full textWe have used polarized Cu K-edge extended x-ray absorption fine structure to investigate the local lattice displacements in the charge-ordered La(1.48)Nd(0.4)Sr(0.12)CuO(4) system. The temperature-dependent distance broadening, given by the Debye-Waller factors of the Cu-O bonds measuring local lattice fluctuations, shows a clear steplike increase below the charge stripe order temperature. The results construct a direct evidence for the local lattice fluctuations as a response function of the charge stripe ordering in the cuprate superconductors
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