Electronic structure and metal-insulator transition in SrTi 1 - x Ru x O 3

PACS. 79.60.Bm Clean metal, semiconductor, and insulator surfaces – 78.70.Dm X-ray absorption spectra – 71.30.+h Metal-insulator transitions and other electronic transitions,

Structure Refinement of (Sr,Ba)Nb2O6 Ceramic Powder from Neutron and X-Rays Diffraction Data

The structure of polycrystalline strontium barium niobate at room temperature was refined by the Rietveld method. Sintered ceramic samples were used to collect powder neutron and X-ray diffraction data. The ratio Sr/Ba ~ 64/36 was found from the initial batch composition Sr0.61Ba0.39Nb2O6, corroborating with the quantitative X-ray dispersive spectroscopy (EDS) measurements. The structure is tetragonal with cell parameters a, b = 12.4504(3) Å and c = 3.9325(1) Å and space group P4bm. It was not necessary to introduce any positional disorder for the oxygen atoms. Cation Nb+5 displacements not parallel to the c direction are presented, which can influence the behavior of the ferroelectric properties

A Crystalline Phase Transition And Optical Properties In A Co Iicuii Oxamato-bridged Ferrimagnetic Chain

The compound [CoCu(opba)(DMSO)3] (1) [opba = orthophenylenebis(oxamato)] has been synthesized and characterized. Its crystal structure has been analyzed by X-ray diffraction techniques at 100 and 298 K. A structural phase-transition has been detected at around 150 K. An orthorhombic crystalline system is found at both temperatures, with very similar unit-cell dimensions. At room temperature 1 crystallizes in the Pnam space group (α-1 phase), with a = 7.6712(2), b = 14.8003(3), c = 21.0028(5) Å, and Z = 4, whereas at low temperature it crystallizes in the Pna21 space group (β-1 phase), with a = 7.3530(2), b = 14.5928(4), c = 21.0510(7) Å, and Z = 4. Both crystalline phases consist of linearly ordered bimetallic chains with the [Cu(opba)]2- units tied by CoII ions to form a one-dimensional system. The DMSO molecules in α-1, which are coordinated to either CuII or CoII, are disordered. At low temperature, a small reorganization of the CuII and Co II environments is observed. 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