Doping Experiments on Low-Dimensional Oxides and a Search for Unusual Magnetic Properties of MgAlB14

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Doping experiments on La{sub 2}CuO{sub 4}, Sr{sub 2}CuO{sub 3} and SrCu{sub 2}(BO{sub 3}){sub 2} were performed with the intent of synthesizing new metallic low-=dimensional cuprate oxide compounds. Magnetic susceptibility {chi}(T) measurements on a polycrystalline La{sub 2}CuO{sub 4} sample chemically oxidized at room temperature in aqueous NaClO showed superconductivity with a superconducting transition temperature T{sub c} of 42.6 K and a Meissner fraction of 26%. They were unable to electrochemically oxidize La{sub 2}CuO{sub 4} in a nonaqueous solution of tetramethylammonium hydroxide (TMAOH) and methanol. Sr{sub 2}CuO{sub 3} was found to decompose upon exposure to air and water. Electron paramagnetic resonance, isothermal ... continued below

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Hill, Julienne Marie December 31, 2002.

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  • Ames Laboratory
    Publisher Info: Ames Lab., IA (United States)
    Place of Publication: Iowa

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Doping experiments on La{sub 2}CuO{sub 4}, Sr{sub 2}CuO{sub 3} and SrCu{sub 2}(BO{sub 3}){sub 2} were performed with the intent of synthesizing new metallic low-=dimensional cuprate oxide compounds. Magnetic susceptibility {chi}(T) measurements on a polycrystalline La{sub 2}CuO{sub 4} sample chemically oxidized at room temperature in aqueous NaClO showed superconductivity with a superconducting transition temperature T{sub c} of 42.6 K and a Meissner fraction of 26%. They were unable to electrochemically oxidize La{sub 2}CuO{sub 4} in a nonaqueous solution of tetramethylammonium hydroxide (TMAOH) and methanol. Sr{sub 2}CuO{sub 3} was found to decompose upon exposure to air and water. Electron paramagnetic resonance, isothermal magnetization M(H), and {chi}(T) measurements on the primary decomposition product, Sr{sub 2}Cu(OH){sub 6}, were consistent with a nearly isolated, spin S = 1/2, local moment model for the Cu{sup +2} spins. From a fit of {chi}(T) by the Curie-Weiss law and of the M(H) isotherms by a modified Brillouin function, the weakly antiferromagnetic exchange interaction between adjacent Cu{sup +2} spins in Sr{sub 2}Cu(OH){sub 6} was found to be J/k{sub B} = 1.06(4) K. Doping studies on SrCu{sub 2}(BO{sub 3}){sub 2} were inconclusive. {chi}(T) measurements on an undoped polycrystalline sample of SrCu{sub 2}(BO{sub 3}){sub 2}, a sample treated with distilled water, and a sample treated with aqueous NaClO showed no qualitative differences between the samples. In addition, {chi}(T) and M(H, T) studies of the ultra-hard material MgAlB{sub 14} were carried out in search of superconductivity or ferromagnetism in this compound. {chi}(T) measurements on a powder sample revealed temperature-independent diamagnetism from 1.8 K up to room temperature with a Curie-Weiss impurity concentration equivalent to {approx} 1 mol% of spin-1/2 ions. In contrast, M(H, T) data on hot pressed samples showed evidence of ferromagnetic transitions above {approx} 330 K. Scanning electron microscopy and Auger microprobe analysis of the hot pressed samples indicated that the observed ferromagnetism was likely due to Fe impurities.

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3647 Kilobytes pages

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INIS; OSTI as DE00806588

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  • Other Information: TH: Thesis (Ph.D.); Submitted to Iowa State Univ., Ames, IA (US)

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  • Report No.: IS-T 2066
  • Grant Number: W-7405-Eng-82
  • Office of Scientific & Technical Information Report Number: 806588
  • Archival Resource Key: ark:/67531/metadc737653

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  • December 31, 2002

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  • Oct. 18, 2015, 6:40 p.m.

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  • Nov. 11, 2015, 6:36 p.m.

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Hill, Julienne Marie. Doping Experiments on Low-Dimensional Oxides and a Search for Unusual Magnetic Properties of MgAlB14, thesis or dissertation, December 31, 2002; Iowa. (digital.library.unt.edu/ark:/67531/metadc737653/: accessed December 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.