Structure and magnetic properties of the pyrochlore iridate Y ₂Ir ₂O ₇

Neutron powder diffraction and inelastic measurements were performed examining the 5d pyrochlore Y ₂Ir ₂O ₇. Temperature-dependent measurements were performed between 3.4 K and 290 K, spanning the magnetic transition at 155 K. No sign of any structural or disorder-induced phase transition was observed over the entire temperature range. In addition, no sign of magnetic long-range order was observed to within the sensitivity of the instrumentation. These measurements do not rule out long-range magnetic order, but the neutron-powder-diffraction structural refinements do put an upper bound for the ordered iridium moment of ∼0.2 μ _B/Ir (for a magnetic structure with wave vector Q*0) or ∼0.5 μ _B/Ir (for Q=0).