Eur. Phys. J. B 14, 73-82 (2000)
https://doi.org/10.1007/s100510050108

Localization effects in the charge density wave state of the quasi-two-dimensional monophosphate tungsten bronzes (PO₂)₄(WO₃)_2m (m = 7, 8, 9 )

¹ Laboratoire d'Études des Propriétés Électroniques des SolidesCNRS, BP 166, 38042 Grenoble Cedex 9, France
² Departamento de Quimica, ITN, 2686 Sacavem Codex, Portugal
³ Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2825 Monte de Caparica, Portugal
⁴ Laboratoire CRISMATCNRS UMR 6508, ISMRA, Université de Caen, 14050 Caen Cedex, France

Received: 16 September 1999
Published online: 15 March 2000

Abstract

The monophosphate tungsten bronzes (PO₂)₄(WO₃)_2mare quasi-two-dimensional conductors which show charge density wave type electronic instabilities. We report electrical resistivity and magnetoresistance measurements down to 0.30 K and in magnetic fields up to 16 T for the m = 7, 8 and 9 members of this family. We show that these compounds exhibit at low temperature an upturn of resistivity and field dependences of the magnetoresistance characteristic of localization effects. We discuss the dimensionality of the regime of localization as m is varied. We show that for m=7, the regime is quasi-two-dimensional and three-dimensional for m= 8, 9.