Heat Capacity of RuO2 and IrO2 between 0.54° and 10°K

The heat capacities of the metallic transition-metal oxides IrO2 and RuO2 have been measured between 0.54° and 10°K. Both compounds exhibited heat capacities characteristic of metals, with contributions due to nuclear quadrupole interactions apparent in the 3He region. The heat capacity of IrO2 was found to be C = 0.308T−2 + 0.0565T3 + 5.51T (mJ/mole·°K). The heat capacity of RuO2 was found to be C = 0.059T−2 + 0.0225T3 + 5.77T (mJ/mole·°K). The results are discussed in relation to electrical resistivity, paramagnetic susceptibility, and Mössbauer effect studies on these materials.