Unconventional magnetic properties of the weakly ferromagnetic metal Ba Ir O 3

We present experimental evidence for small-moment magnetism below the ferromagnetic transition temperature $({T}_{\mathrm{c}3}=183\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ 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 $({T}_{\mathrm{c}1}=26\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. These results are only possible via muon-spin relaxation $(\ensuremath{\mu}\mathrm{SR})$ 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 $\ensuremath{\mu}\mathrm{SR}$, 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.