Chemical Pressure effect at the boundary of Mott insulator and itinerant electron limit of Spinel Vanadates

The effect of chemical pressure on the structural, transport, magnetic and electronic properties of ZnV2O4 has been investigated by doping Mn and Co onto the Zn sites of ZnV2O4. With Mn doping the V-V distance increases and with Co doping it decreases. The resistivity and thermoelectric power data indicate that, as the V-V distance decreases, the system moves towards quantum phase transition. The transport data also indicate that the conduction is due to small polaron hopping. The chemical pressure shows a non-monotonous behaviour of charge gap and activation energy. On the other hand, when Ti is doped on the V-site of ZnV2O4, the metal metal distance decreases and, at the same time, T-N also increases.