Structure and Magnetic Properties of the Pyrochlore Iridate Y2Ir2O7

Neutron powder diffraction and inelastic measurements were performed examining the 5d pyrochlore Y$_2$Ir$_2$O$_7$. 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 $\sim$ 0.2 $\mu_B /$Ir (for a magnetic structure with wave vector $Q \neq 0$) or $\sim$ 0.5 $\mu_B /$Ir (for Q = 0).