We present experimental evidence for small-moment magnetism below the ferromagnetic transition temperature $(T_{\mathrm{c}3}=183\mathrm{K})$ in the quasi-one-dimensional metal $\mathrm{Ba}\mathrm{Ir}{\mathrm{O}}_3$. Further, we identify rearrangement of the local magnetic moment distribution, which leaves the bulk magnetization unchanged, at the Mott-like transition $(T_{\mathrm{c}1}=26\mathrm{K})$. These results are only possible via muon-spin relaxation $\left(\mu \mathrm{SR}\right)$ 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 $\mu \mathrm{SR}$, 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.

• Received 6 April 2005

DOI:https://doi.org/10.1103/PhysRevB.71.220411