期刊
JOURNAL OF PHYSICS D-APPLIED PHYSICS
卷 41, 期 19, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0022-3727/41/19/195001
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资金
- CYCIT [MAT2006-10021, CCG06-UCM/MAT-1333]
Perovskite-type cobaltites LaCo1-xTixO3 (0 <= x <= 0.5) synthesized by the liquid mix technique were characterized by x-ray diffraction, neutron diffraction, XPS, magnetic susceptibility and magnetization versus magnetic field measurements. Structural symmetry changes from rhombohedral (S. G. R (3) over barc) for 0.05 <= x <= 0.20 to orthorhombic (S. G. Pbnm) for 0.25 <= x <= 0.40. The bond distances dependence on the composition, x, has been analysed from x-ray and neutron diffraction data. Both the structural and the spectroscopic (from XPS) results suggest that Ti4+ substitution implies the stabilization of low-spin Co-III ions and the evolution of magnetic moments in the paramagnetic zone is also coherent with this assumption. For small values of x both FM responses and the absence of saturation in the M versus H curves at 2K are interpreted in terms of a magnetic frustration. For x > 0.25 the cobalt cations seem to stabilize as CoIII (rather than Co3+) coexisting with Co2+. In these more substituted perovskites, AFM Co2+-O-Co2+ interactions become predominant, leading to a well established AFM ordering for x = 0.4 and 0.5.
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