Volume 81, Number 4, February 2008
Article Number 47005
Number of page(s) 4
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 22 January 2008
EPL, 81 (2008) 47005
DOI: 10.1209/0295-5075/81/47005

Transport and pressure properties of $\chem{Na_{0.5-\delta}CoO_2}$ single crystals with metallic ground state

G. Garbarino1, F. Morales1, M. Núñez Regueiro1, M. Armand2 and P. Lejay1

1  Institut NEEL, CNRS and Université Joseph Fourier - BP 166 Bât E, F-38042 Grenoble Cedex 9, France
2  Laboratoire réactivité et chimie des solides (LRCS), Université Picardie Jules-Verne Amiens - 33, Rue Saint-Leu, F-80039 Amiens Cedex 1, France

received 24 October 2007; accepted in final form 18 December 2007; published February 2008
published online 22 January 2008

We report transport properties as a function of temperature and pressure up to 16 GPa in single crystals of NaxCoO2. Our x = 0.5-$\delta$ samples, obtained by a novel de-intercalation method, present the transitions characteristic of x = 0.5 samples, albeit with a metallic ground state at low temperatures. Besides the obvious consequences of the sub-stoichiometry of our samples, we present evidence suggesting that an insulator state can be induced by disorder that localizes the few carriers left after the transitions.

72.80.Ga - Transition-metal compounds.
61.50.Ks - Crystallographic aspects of phase transformations; pressure effects.
62.50.+p - High-pressure and shock wave effects in solids and liquids.

© EPLA 2008