Spin-state ordering and magnetic structures in the cobaltites YBaCo{sub 2}O{sub 5+{delta}} ({delta}=0.50 and 0.44)
- Institute of Solid State and Semiconductors Physics, National Academy of Sciences, P. Brovka Street 17, 220072 Minsk (Belarus)
The antiferromagnetic-ferromagnetic phase transition in YBaCo{sub 2}O{sub 5.50} and YBaCo{sub 2}O{sub 5.44} cobaltites with different types of oxygen-ion ordering in the [YO{sub 0.5/0.44}] layers has been studied by neutron powder diffraction in combination with group-theoretical analysis. As a result, the crystal and magnetic structures above and below the phase transformation temperature T{sub i} were determined and successfully refined. In both cases, the proposed models involve a spin-state ordering between diamagnetic (t{sub 2g}{sup 6}e{sub g}{sup 0}, S=0) and paramagnetic (t{sub 2g}{sup 4}e{sub g}{sup 2}, S=2) Co{sup 3+} ions with octahedral coordination. Electronic ordering results in a nonzero spontaneous magnetic moment in the high-temperature magnetic phases with isotropic negative exchange interactions. In the case of YBaCo{sub 2}O{sub 5.5}, the phase transformation does not change the Pmma (2a{sub p}x2a{sub p}x2a{sub p}) symmetry of the crystal structure. The wave vectors of magnetic structures above and below T{sub i} are k=0 and k=c*/2, respectively. In the case of YBaCo{sub 2}O{sub 5.44} a crossover P4/nmm (3{radical}(2)a{sub p}x3{radical}(2)a{sub p}x2a{sub p}){yields}I4/mmm (3{radical}(2)a{sub p}x3{radical}(2)a{sub p}x4a{sub p}) was involved to solve the low-temperature magnetic structure. The wave vectors in both high-temperature and low-temperature magnetic phases are k=0. Mechanisms of the phase transformation in both compositions are discussed in the light of obtained magnetic structures. The proposed spin configurations were compared with other models reported in literature.
- OSTI ID:
- 20957789
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 75, Issue 13; Other Information: DOI: 10.1103/PhysRevB.75.134407; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANTIFERROMAGNETISM
BARIUM COMPOUNDS
COBALT IONS
CRYSTAL STRUCTURE
LAYERS
MAGNETIC MOMENTS
NEUTRON DIFFRACTION
OXYGEN IONS
PARAMAGNETISM
PHASE TRANSFORMATIONS
PMMA
SPACE GROUPS
SPIN
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0400-1000 K
VECTORS
YTTRIUM COMPOUNDS