Low temperature electrical transport properties of RuO₂ and IrO₂ single crystals

We have systematically measured the electrical transport properties of several RuO₂ and IrO₂ single crystals over a wide temperature range from 300 K down to 0.3 K to study the conduction mechanisms in these oxides. Our measured resistivities are in close agreement with the recent band-theory calculations for these materials. The characteristic temperatures for the acoustic-mode and optical-mode phonons are determined. Our measured magnetoresistances are positive and follow the Kohler rule, indicating that the transport properties of these oxides exhibit normal behaviour as described by the Boltzmann equation. In contrast, we do not find any signature of superconductivity down to 0.3 K, though the band-theory calculations predict a superconducting transition temperature of ∼5 K. Magnetization measurements suggest a very low level of paramagnetic impurities in our crystals.