We present experimental evidence for small-moment magnetism below the ferromagnetic transition temperature (Tc3=183K) in the quasi-one-dimensional metal BaIrO3. Further, we identify rearrangement of the local magnetic moment distribution, which leaves the bulk magnetization unchanged, at the Mott-like transition (Tc1=26K). These results are only possible via muon-spin relaxation (μSR) techniques, since neutron scattering studies are hindered by the large absorption of neutrons by Ir. The low-temperature characteristics of this compound, as revealed by μSR, are unconventional, and suggest that its magnetic properties are driven by changes occurring at the Fermi surface due to the formation of a charge-density wave state. © 2005 The American Physical Society.
