Quasi two-dimensional antiferromagnet SrRu₂O₆: mechanism of electrical conduction

The electronic ground state in the layered antiferromagnetic compound SrRu2O6is semiconducting. However, the band gap estimated from fitting of the Arrhenius model to the high temperature region (300-200 K) of the electrical- transport data in SrRu2O6is typically found to be significantly smaller than the theoretically predicted value. Here we show that in the high-temperature region, the Arrhenius, variable range hopping (VRH), and modified VRH exhibit similar goodness of fit when fitted to transport data. Interestingly, the fluctuation-induced tunneling (FIT) model is observed to exhibit an excellent fit in a much wider temperature range. For SrRu2O6, which inherently possesses a quasi-two-dimensional crystal structure, the FIT model points towards the intriguing possibility of thermal-fluctuation-induced tunnelling of charge carriers across the conducting and insulating layers. We also explored the role of morphology and defects in a number of SrRu2O6samples prepared in different batches. Data on multiple samples bring out the profound role of intrinsic defects and associated strain in the nature of electrical conduction, especially at lower temperatures.