Magnetotransport and charge density wave instabilities in the quasi-two-dimensional phosphate tungsten bronzes (PO 2) 4(WO 3) 2m (m = 4,6,7)

Abstract

Electrical resistivity has been measured between 4.2 K and 300 K in fields up to 6 Tesla on the monophosphate tungsten bronzes P 4W 8O 32, P 4W 12O 44 and P 4W 14O 50. These compounds are anisotropic quasi-two-dimensional metals showing several charge density wave instabilities. For m = 4 and m = 6, a large anisotropic magnetoresistance is found in the lowest temperature charge density wave state, as expected, with small carrier pockets left on the Fermi surface by gap openings. For m = 7, several instabilities are found by the transport properties together with a small magnetoresistance. These results are partly consistent with X-ray diffuse scattering studies.