Search

We report on the effect of Nb substitution on the lattice evolution and magnetic properties of the Ce 1− x Nb x O 2 . Based on the microstructure analysis the solubility limit of Nb was revised to x = 0.03. The lattice response to the Nb dopant shows unexpected non-monotonic dependence which cannot be described by an ideal solution of non-interacting point defects. By slow cooling, quenching, and sealed sample anneals, the ideal solution model, including oxygen vacancies, Nb dopant, and oxygen interstitials as key defects does not adequately describe the observed concentration of Ce 3+ . Magnetic measurements reveal that for ceramics prepared in air at ambient pressure the concentration of Ce 3+ ions linearly increases with Nb content at approximately 1:2 ratio up to the Nb solubility limit. The effect of the crystal field on the energy splitting between the Ce 3+ Γ8 and Γ7 multiplets shows strong dependence on the Nb concentration especially at low doping levels. This serves as an evidence of the possible point defect association in the title compound even at a very diluted Nb concentration. [ABSTRACT FROM AUTHOR]

Ca 9.5–1.5 x Bi x Cd(VO 4 ) 7 (0 ≤ x ≤ 1) solid solutions with the whitlockite-type structure (SG R 3 c ) were synthesized by a standard solid-state method in air. Structures of Ca 9.5–1.5 x Bi x Cd(VO 4 ) 7 ( x = 0.167, 0.5, 0.833) were refined by the Rietveld method from synchrotron powder X-ray diffraction data. Nonlinear optical properties of the whitlockite-type compounds can be designed and increased by an order of magnitude through appropriate isovalent and aliovalent substitutions for Ca 2+ cations. Dielectric and temperature second harmonic generation investigations revealed the presence of a reversible ferroelectric phase transition in the range from 1331 K to 1055 K. The phase transition temperature monotonically decreases while nonlinear optical activity of Ca 9.5–1.5 x Bi x Cd(VO 4 ) 7 strongly increases with increasing Bi 3+ content. [ABSTRACT FROM AUTHOR]

Highlights: [•] The detailed P–T phase diagram of BiMnO3 was established. [•] We found three monoclinic modifications of BiMnO3 at pressure and temperature. [•] A suppression of monoclinic C2/c phase have been observed under pressure. [•] We found a new orthorhombic Imma phase of BiMnO3 at P >20GPa. [Copyright &y& Elsevier]

Abstract: A new inverse spinel ScMn2O4 has been synthesized and characterized by measurements of structural and physical properties. The crystal structure of ScMn2O4, similar with the spinel Mn3O4, is made up of Mn2+ located at tetrahedral site and Mn3+/Sc3+ ions randomly located at the octahedral site. Experimental results of magnetic susceptibility and heat capacity demonstrate that ScMn2O4 undergoes a ferrimagnetic phase transition at the temperature of about 58K. Extensive analyses on the data obtained from structural refinement, electronic structural calculation and EELS spectra measurement suggests that substitution of Sc for Mn in MnO6 octahedron could greatly suppress Jahn–Teller distortions in comparison with what observed in Mn3O4. [Copyright &y& Elsevier]

Abstract: Submillimeter and millimeter wave ESR measurements of spin gap systems SrCu2(PO4)2 and PbCu2(PO4)2, which have four kinds of dimers, have been performed to investigate the magnetic properties of spin gap systems using the pulsed magnetic field up to 35T. The observed ESR spectra of powder sample SrCu2(PO4)2 show sharp and single peak in the temperature range from 4.2 to 80K. The anisotropy of the g-values turned out to be very small compared to the usual anisotropic powder spectra of copper compounds. The dynamical properties will be discussed from the temperature dependence measurements. [Copyright &y& Elsevier]

Abstract: Oxygen vacant superconductors LaFeAsO1− δ were synthesized under a high-pressure condition. A bell-shaped feature in Tc vs. δ was observed for LaFeAsO1− δ as well as TbFeAsO1− δ . The optimized Tc was achieved at δ of 0.15, being comparable with that for TbFeAsO1− δ . The relatively wide δ window of LaFeAsO1− δ may merit scientific and technical studies of high-Tc superconductivity. [ABSTRACT FROM AUTHOR]