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

doi:10.1103/PhysRevLett.92.017602

paper

Dome-shaped magnetic phase diagram of thermoelectric layered cobaltites

arXiv:cond-mat/0310516 · doi:10.1103/PhysRevLett.92.017602

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.

4 pages, 4 figures, 1 table