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Start Over Author "A. Cava" Journal journal of solid state chemistry
316 results on '"A. Cava"'

34. Synthesis and characterization of the novel antiferromagnet LaNiB3O7

Author

Shu Guo, Elizabeth M. Carnicom, R. J. Cava, Karoline Stolze, and Kelly M. Powderly

Subjects
Materials science, Magnetism, chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Inorganic Chemistry, Condensed Matter::Materials Science, chemistry.chemical_compound, Lanthanum oxide, Materials Chemistry, Antiferromagnetism, Physical and Theoretical Chemistry, Magnetic moment, Nickel oxide, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Magnetic susceptibility, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Crystallography, Nickel, chemistry, Ceramics and Composites, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology, Néel temperature
Abstract

We present the synthesis, structure, and magnetic properties of the novel borate LaNiB3O7 – the first magnetically ordered compound reported in the CaAlB3O7 structure type. This material is made of alternating sheets of corner-sharing borate tetrahedra and planes of La and Ni ions, with distorted nickel oxide [NiO6] octahedra and lanthanum oxide [LaO10] polyhedra. Temperature-dependent magnetic susceptibility data reveal dominantly antiferromagnetic interactions and an antiferromagnetic transition with a Neel temperature of 19 K, confirmed by specific heat data. The magnetic moment per nickel ion is 3.06 μB. This compound uncovers a new family of rare-earth transition-metal borates to probe for magnetic interactions.

Published
2019
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42. Crystal structure and elementary properties of PbS2 with a pressure–stabilized S-S dimer

Author

F. Alex Cevallos, Robert J. Cava, Danrui Ni, Tai Kong, Shu Guo, Ruidan Zhong, Jingjing Lin, and Kelly M. Powderly

Subjects
Materials science, business.industry, 02 engineering and technology, Crystal structure, Electronic structure, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Degenerate semiconductor, Inorganic Chemistry, Crystallography, Semiconductor, Electrical resistivity and conductivity, Seebeck coefficient, Materials Chemistry, Ceramics and Composites, Direct and indirect band gaps, Physical and Theoretical Chemistry, 0210 nano-technology, business, Single crystal
Abstract

PbS2 and Pb0.9Ag0.1S2 were prepared through the reaction of PbS with excess sulfur (and silver) at 4 GPa and 600 °C. PbS2 crystallizes in the CuAl2 structure type, (I4/mcm (#140), a = 6.1106(5) A, c = 7.4949(6) A, Z = 4), determined by single crystal X-ray diffraction. Its structure consists of layers of [S2]2- dimers and Pb2+ in square antiprismatic coordination – a rare structure type for metal dichalcogenides. Electronic structure calculations suggest that the material should be an indirect band gap semiconductor. Consistent with the calculations, the temperature-dependent resistivity of undoped PbS2 is that of a degenerate semiconductor, while the Ag-doped material shows metallic temperature dependent resistivity down to 2 K. The materials are both diamagnetic. For the Ag-doped material, the Seebeck coefficient is small and shows nearly linear temperature-dependent behavior from 50 to 250 K.

Published
2019
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43. The homometallic warwickite V2OBO3

Author

Tomasz Klimczuk, Karolina Górnicka, Elizabeth M. Carnicom, and Robert J. Cava

Subjects
Diffraction, Crystallographic point group, Materials science, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Magnetic susceptibility, Synchrotron, Electronic, Optical and Magnetic Materials, law.invention, Inorganic Chemistry, Crystallography, Ferrimagnetism, law, Electrical resistivity and conductivity, Lattice (order), 0103 physical sciences, Materials Chemistry, Ceramics and Composites, Orthorhombic crystal system, Physical and Theoretical Chemistry, 010306 general physics, 0210 nano-technology
Abstract

The synthesis, structure and elementary magnetic characterization of the homometallic warwickite V2OBO3 are reported. The material adopts the orthorhombic warwickite structure type at room temperature, space group Pnma (No. 62) with lattice parameters a = 9.2317(1) A, b = 3.1172(1) A, and c = 9.5313(1) A. Temperature-dependent magnetic susceptibility, electrical resistivity, and specific heat measurements show anomalies near 35 K, between 135 K and 150 K, and near 260 K, with the transition at ~ 35 K likely to a ferrimagnetic state. High resolution synchrotron powder X-ray diffraction data at temperatures between 295 K and 90 K display significant peak splitting upon cooling, indicating that at least one crystallographic symmetry change occurs at low temperatures.

Published
2018
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44. La15NbxGe9: a superstructure of the Mn5Si3 structure type with interstitial Nb atoms

Author

Joanna Blawat, M. Roman, Tomasz Klimczuk, Weiwei Xie, and Robert J. Cava

Subjects
Superconductivity, Materials science, 02 engineering and technology, Crystal structure, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Heat capacity, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Inorganic Chemistry, symbols.namesake, Crystallography, Electrical resistivity and conductivity, Formula unit, Materials Chemistry, Ceramics and Composites, symbols, Crystallite, Physical and Theoretical Chemistry, 0210 nano-technology, Ternary operation, Debye model
Abstract

The crystal structure and elementary properties of La15NbxGe9 are reported. Single-crystal X-ray diffraction, from a crystallite with only 0.12 Nb/formula unit, reveals that this compound, although transition metal deficient, crystallizes in a hexagonal “15-1-9”-like structure type, space group P63mc (no. 186) with lattice parameters a = b = 15.5017(2) A, c = 6.9173(2) A. The physical properties were examined by specific heat and resistivity measurements. La15Nb0.4Ge9 shows metallic behavior, and no superconductivity is observed above 0.4 K. The Sommerfeld coefficient (γ = 62.41(8) mJ mol−1 K−2) and the Debye temperature ( θ D = 267(1) K) were estimated from a fit to the low temperature heat capacity data. La15Nb0.4Ge9 is the first reported compound in the ternary La-Nb-Ge system.

Published
2018
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