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

TL;DR

This study investigates how chemical pressure, induced by doping, affects the structural, electronic, and magnetic properties of ZnV2O4, revealing a transition towards a quantum phase transition and changes in conduction mechanisms.

Contribution

It provides new insights into how doping-induced chemical pressure influences the Mott insulator to itinerant electron boundary in spinel vanadates.

Findings

V-V distance increases with Mn doping and decreases with Co doping.

System approaches quantum phase transition as V-V distance decreases.

Conduction occurs via small polaron hopping, with non-monotonous charge gap behavior.

Abstract

The chemical pressure effect on the structural, transport, magnetic and electronic properties (by measuring X-ray photoemission spectroscopy) of ZnV2O4 has been investigated by doping Mn and Co on the Zinc site 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 the small polaron hopping. The chemical pressure shows the non-monotonous behaviour of charge gap and activation energy. The XPS study also supports the observation that with decrease of the V-V separation the system moves towards Quantum Phase Transition. On the other hand when Ti is doped on the V-site of ZnV2O4 the metal-metal distance decreases and at the same time the TN also increases.