Here we report the magnetic properties of the layered cobalt oxide system, ${\text{Li}}_x{\text{CoO}}_2$, in the whole range of Li composition, $0\le x\le 1$. Based on dc-magnetic-susceptibility data, combined with results of ${}^{59}\text{Co}$ nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) observations, the electronic phase diagram of ${\text{Li}}_x{\text{CoO}}_2$ has been established. As in the related material ${\text{Na}}_x{\text{CoO}}_2$, a magnetic critical point is found to exist between $x=0.35$ and 0.40, which separates the Pauli-paramagnetic and Curie-Weiss metals. In the Pauli-paramagnetic regime $\left(x\le 0.35\right)$, the antiferromagnetic spin correlations systematically increase with decreasing $x$. Nevertheless, ${\text{CoO}}_2$, the $x=0$ end member is a noncorrelated metal in the whole temperature range studied. In the Curie-Weiss regime $\left(x\ge 0.40\right)$, on the other hand, various phase transitions are observed. For $x=0.40$, a susceptibility hump is seen at 30 K, suggesting the onset of static antiferromagnetic order. A magnetic jump, which is likely to be triggered by charge ordering, is clearly observed at $T_{\text{t}}\approx 175\text{K}$ in samples with $x=0.50$ $\left(=1/2\right)$ and 0.67 $\left(=2/3\right)$, while only a tiny kink appears at $T\approx 210\text{K}$ in the sample with an intermediate Li composition, $x=0.60$. Thus, the phase diagram of the ${\text{Li}}_x{\text{CoO}}_2$ system is complex and the electronic properties are sensitively influenced by the Li content $\left(x\right)$.

• Received 23 April 2009

DOI:https://doi.org/10.1103/PhysRevB.80.165114