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Sixpack charge order in β-Na1/3V2O5



Transition-metal oxides form a variety of low-dimensional structures built by formations of oxygen polyhedra and exhibit a wide spectrum of exceptional electronic and magnetic properties.

Some years ago the one-dimensional vanadium bronze β-Na1/3V2O5 attracted new attention when one-dimensional conductivity in stoichiometric samples was discovered.
The metallic phase is observed above 130 K, where a metal-to-insulator transition (MIT) takes place due to charge order. A series of investigations started to clarify the peculiarities of the MIT, but both the conduction mechanism and the charge distribution are still heavily under debate.

β-Na1/3V2O5 crystallizes in a monoclinic crystal structure building three inequivalent vanadium chains parallel to the crystallographic b axis. Since each Na atom donates one electron to the empty vanadium d bands, the sixth part of the vanadium atoms has electron configuration 3d1.
Therefore, ESR is ideally suited for the investigation of the magnetic properties of this vanadium system, since the V4+ ions can be used as a microscopic probe of the spin system. In particular, an ESR investigation of β-Na1/3V2O5 allows for the direct observation of the charge-ordering process.

The angular and temperature dependent investigations have been performed on β-Na1/3V2O5 single crystals of high quality, because already small deviations of the Na concentration x=1/3 inhibit the existence of the metallic phase and lead to semiconducting behaviour.


na ladders

 

Important information can be derived:

 

To learn more, see:
M. Heinrich, H.-A. Krug von Nidda, R. M. Eremina, A. Loidl, Ch. Helbig, G. Obermeier, and S. Horn, Phys. Rev. Lett. 93, 116402 (2004).