Electrical, structural and magnetic properties of pure and doped 1T-TaS₂

A review of the available electrical and structural data on both pure and doped 1T-TaS2 leads us to propose that the nearly commensurate to commensurate transition at 200 K is accompanied by Mott localization in two dimensions. One electron out of 13 in the Ta plane is localized onto the centre of a star of 13 Ta atoms. The picture helps in understanding the concentration dependence of the low-temperature resistivity in cation-doped samples, particularly the sharp maximum at an atomic fraction x ∼ 0.08 for Ti doping. Examining recent resistivity data by Di Salvo and Graebner (1977) we find that at low temperatures the conduction mechanism assumes a three-dimensional character. The lack of a Curie-type susceptibility in spite of electron localization is ascribed to spin-orbit coupling, according to an earlier suggestion by Geertsma, Haas, Huisman and Jellinek (1972).