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Doping induced magnetic clusters and Co spin state transition in Na_xCoO_2 with 0.78<x<.97

C. Bernhard·Ch. Niedermayer·A. Drew·G. Khaliullin·S. Bayrakci·J. Strempfer·R. K. Kremer·D. P. Chen·C. T. Lin·B. Keimer
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Abstract

By muon spin rotation we investigated the magnetic properties of a series of highly Na doped NaxCoO2 single crystals with 0.78(1) 0.04 until they yield a bulk magnetic state near x=0.78. Evidence for a strong (likely geometrical) frustration of the magnetic order is obtained from the anomalous doping dependence of the spin fluctuation rate (above the ordering temperature) which is strongly enhanced at x=0.78 as compared to x=0.97.

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C. Bernhard, Ch. Niedermayer, A. Drew, G. Khaliullin, S. Bayrakci, J. Strempfer, R. K. Kremer, D. P. Chen, C. T. Lin, B. Keimer. 2007-10-04. Doping induced magnetic clusters and Co spin state transition in Na_xCoO_2 with 0.78<x<.97. https://arxiv.org/abs/cond-mat/0701033

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