Structural and magnetic study of

L Suescun, CY Jones, CA Cardoso, JW Lynn… - Physical Review B …, 2005 - APS
Physical Review B—Condensed Matter and Materials Physics, 2005APS
The structure and magnetic properties of the compound La Ba Cu Co O 5+ δ have been
studied for the non-stoichiometric oxygen concentration δ≈ 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 P
mmm space group, with cell parameters a= 3.9223 (3) Å, b= 3.9360 (3) Å, c= 11.7073 (8) Å,
and V= 180.74 (2) Å 3 (room temperature). Antiferromagnetic ordering of Cu and Co …
The structure and magnetic properties of the compound have been studied for the non-stoichiometric oxygen concentration . 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 space group, with cell parameters , , , and (room temperature). Antiferromagnetic ordering of Cu and Co magnetic moments is observed below . The magnetic structure with cell , , and , could be described with the Shubnikov space group . The magnetic moments of both equivalent sites were determined at 50 and to be and , 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 while a three dimensional Heisenberg model could improve the fit. Susceptibility measurements between 4 and also show irreversibility below . 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.
American Physical Society
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