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Dome-shaped magnetic phase diagram of thermoelectric layered cobaltites

J. Sugiyama·J. H. Brewer·E. J. Ansaldo·H. Itahara·T. Tani·M. Mikami·Y. Mori·T. Sasaki·S. Hebert·A. Maignan
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Abstract

Using muon spin spectroscopy we have found that, for both Na$_x$CoO$_2$ (0.6 $\leq x \leq$ 0.9) and 3- and 4-layer cobaltites, a common low temperature magnetic state (which in some cases is manifest as an incommensurate spin density wave) forms in the CoO$_2$ planes. Here we summarize those results and report a dome-shaped relation between the transition temperature into the low-$T$ magnetic state and the composition $x$ for Na$_x$CoO$_2$ and/or the high-temperature asymptotic limit of thermopower in the more complex 3- and 4-layer cobaltites. This behavior is explained using the Hubbard model on two-dimensional triangular lattice in the CoO$_2$ plane.

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J. Sugiyama, J. H. Brewer, E. J. Ansaldo, H. Itahara, T. Tani, M. Mikami, Y. Mori, T. Sasaki, S. Hebert, A. Maignan. 2003-10-22. Dome-shaped magnetic phase diagram of thermoelectric layered cobaltites. https://doi.org/10.1103/physrevlett.92.017602

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