Specific heat and transport study of the co-existence of charge-density-wave and weak ferromagnetism in BaIrO₃

Abstract

Monoclinic BaIrO₃ was reported to display simultaneous onset of charge density wave transition (CDW) and weak ferromagnetic ordering of Ir moments at T_c=175 K. In this work, we present heat capacity, resistivity, thermopower and thermal conductivity measurements on a high-quality polycrystalline BaIrO₃ sample. The specific heat evidences a well defined mean field like anomaly, much larger than that reported for a single crystal, and at a slightly higher T_c=183 K. The increase of the resistivity below T_c is also much larger than in previous investigation, and the semiconducting behavior at low temperature is much more pronounced. The onset of the CDW leads to a strong increase of the thermopower, from a few μV/K above T_c up to nearly 300μV/K at 70 K, supporting a strong decrease of the charge carrier density and the opening of a gap at T_c. In contrast, no anomaly is observed at T_c in the thermal conductivity, which is dominated by phonon contributions.