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

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 mu V/K above T-c up to nearly 300 mu V/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. (c) 2005 Elsevier B.V. All rights reserved.