Hopping Conductivity in One-Dimensional Ca3Co2O6 Single Crystal

We studied the electronic conductivity of the quasi-one dimensional Ca₃Co₂O₆ single crystal. The results evidence a VRH conductivity with temperature-induced crossover between ID (intra-chain) and 3D transport and the opening of a Coulomb gap in the d bands. At low temperatures, an applied magnetic field induces a large negative magneto-resistance (MR) independent from the 3D magnetic ordering. Both spin-dependent hopping and field-induced suppression of the Coulomb gap are discussed.