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arXiv · 0705.0529

Itinerant and localized magnetism on the triangular lattice: sodium rich phases of Na$_x$CoO$_2$

Meng Gao·Sen Zhou·Ziqiang Wang
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Abstract

We study the interplay between correlation, itinerant ferromagnetism and local moment formation on the electron doped triangular lattice of sodium cobaltates Na$_x$CoO$_2$. We find that strong correlation renormalizes the Stoner criterion and stabilizes the paramagnetic state for $x x_c$, ferromagnetic (FM) order emerges. The enhanced Na dopant potential fluctuations play a crucial role in the sodium rich phases and lead to an inhomogeneous FM state, exhibiting nonmagnetic Co$^{3+}$ patches, antiferromagnetic (AF) correlated regions, and FM clusters with AF domains. Hole doping the band insulator at x=1 leads to the formation of local moments near the Na vacancies and AF correlated magnetic clusters. We explain recent observations by neutron, $μ$SR, and NMR experiments on the evolution of the magnetic properties in the sodium rich phases.

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Meng Gao, Sen Zhou, Ziqiang Wang. 2007-11-13. Itinerant and localized magnetism on the triangular lattice: sodium rich phases of Na$_x$CoO$_2$. https://doi.org/10.1103/physrevb.76.180402

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