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Type: Artigo de periódico
Title: Structural and magnetic study of LaBaCoCuO5+delta
Author: Suescun, L
Jones, CY
Cardoso, CA
Lynn, JW
Toby, BH
Araujo-Moreira, FM
de Lima, OF
Pardo, H
Mombru, AW
Abstract: The structure and magnetic properties of the compound LaBaCuCoO5+delta have been studied for the non-stoichiometric oxygen concentration delta approximate to 0.6. The structure is pseudo-cubic with a tripled perovskite unit cell. The crystal structure was determined by a combined Rietveld fit to neutron and synchrotron x-ray powder diffraction data in the orthorhombic Pmmm space group, with cell parameters a=3.9223(3) angstrom, b=3.9360(3) angstrom, c=11.7073(8) angstrom, and V=180.74(2) angstrom(3) (room temperature). Antiferromagnetic ordering of Cu and Co magnetic moments is observed below 205(4) K. The magnetic structure with cell a(M)=2a, b(M)=2b, and c(M)=2c, could be described with the Shubnikov space group Fmmm'. The magnetic moments of both equivalent Cu/Co sites were determined at 50 and 170 K to be 0.83(3)mu(B) and 0.58(3)mu(B), respectively, consistent with one unpaired electron per atom. The fit of the intensities to a simple mean field magnetic model appeared to be insufficient to account for the variation of moments at temperatures close to T-N while a three dimensional Heisenberg model could improve the fit. Susceptibility measurements between 4 and 350 K also show irreversibility below 150 K. The local environments of Cu and Co were studied by extended x-ray absorption fine structure spectroscopy at both absorption edges. Cu atoms adopt an elongated octahedral or square-based pyramidal oxygen environment which suggests mainly the presence of Cu(II) in the structure. Co adopts different local environments, depending on the electronic and spin states.
Country: EUA
Editor: American Physical Soc
Citation: Physical Review B. American Physical Soc, v. 71, n. 14, 2005.
Rights: aberto
Identifier DOI: 10.1103/PhysRevB.71.144405
Date Issue: 2005
Appears in Collections:Unicamp - Artigos e Outros Documentos

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