SUGIYAMA, J.; NOZAKI, H.; BREWER, J. H.; ANSALDO, E. J.; MORRIS, G. D.; DELMAS, Claude

doi:10.1016/j.physb.2005.11.039

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SUGIYAMA, J.
Central Research and Development Laboratory

NOZAKI, H.
Central Research and Development Laboratory

BREWER, J. H.
Canadian Institute for Advanced Research [CIFAR]
Department of Physics and Astronomy [Vancouver]
TRIUMF [Vancouver]

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Physica B: Condensed Matter. 2006, vol. 374-375, p. p. 148-151

Elsevier

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Magnetism of the simplest layered cobalt oxide, LixCoO2 with x=1.0, 0.95, and 0.7, has been investigated by µ+ SR spectroscopy together with magnetic susceptibility measurements, using polycrystalline samples in the temperature range between 300 and 1.8 K. Weak transverse field µ+ SR showed the appearance of magnetism below ~65 K (=T on c) for the sample with x=1.0. The volume fraction of the magnetic phase at 1.8 K is determined to be ~20 % for LiCoO2, strongly suggesting that the observed magnetism is not induced by impurities but is an intrinsic behavior. This indicates that either a charge disproportionation (2Co3+→Co2++Co4+) or a spin state transition (t 6 2g -> t 5 2g e 1g) occurs below 65 K. Zero field µ+ SR spectra of LiCoO2 consist mainly of a slow relaxing signal due to random fields, even at 1.8 K, plus a small amount of a fast relaxing signal and an oscillating component, implying the presence of an antiferromagnetic order, as in the case of NaxCoO2 with x > 0.75. For Li-deficient LixCoO2 samples, T on c decreases with decreasing x from 50 K for x=0.95 to 25 K for x=0.7. The volume fraction of the magnetic phase is however almost independent of x and is estimated as 20% at 1.8 K, but no oscillations were observed in the zero field spectrum.< Réduire

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Muon spin rotation and relaxation

Critical phenomena

Antiferromagnet

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Frustated magnetism in the two-dimensional triangular lattice of LixCoO2

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