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Localized versus itinerant magnetic moments in Na0.72CoO2

J. L. Gavilano·B. Pedrini·K. Magishi·J. Hinderer·M. Weller·H. R. Ott·S. M. Kazakov·J. Karpinski
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Abstract

Based on experimental 59Co-NMR data in the temperature range between 0.1 and 300 K, we address the problem of the character of the Co 3d-electron based magnetism in Na0.7CoO2. Temperature dependent 59Co-NMR spectra reveal different Co environments below 300 K and their differentiation increases with decreasing temperature. We show that the 23Na- and 59Co-NMR data may consistently be interpreted by assuming that below room temperature the Co 3d-electrons are itinerant. Their magnetic interaction appears to favor an antiferromagnetic coupling, and we identify a substantial orbital contribution corb to the d-electron susceptibility. At low temperatures corb seems to acquire some temperature dependence, suggesting an increasing influence of spin-orbit coupling. The temperature dependence of the spin-lattice relaxation rate T1-1(T) confirms significant variations in the dynamics of this electronic subsystem between 200 and 300K, as previously suggested. Below 200 K, Na0.7CoO2 may be viewed as a weak antiferromagnet with TN below 1 K but this scenario still leaves a number of open questions.

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J. L. Gavilano, B. Pedrini, K. Magishi, J. Hinderer, M. Weller, H. R. Ott, S. M. Kazakov, J. Karpinski. 2005-12-22. Localized versus itinerant magnetic moments in Na0.72CoO2. https://doi.org/10.1103/physrevb.74.064410

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