Magnetic Order in the Pyrochlore Iridates A2Ir2O7 (A = Y, Yb)
  We present results from muon spin relaxation/rotation, magnetization, neutron scattering and transport measurements on polycrystalline samples of the pyrochlore iridates Y2Ir2O7 (Y-227) and Yb2Ir2O7 (Yb-227). Well-defined spontaneous oscillations of the muon asymmetry are observed together with hysteretic behavior in magnetization below 130 K in Yb-227, indicative of commensurate long-range magnetic order. Similar oscillations are observed in Y-227 below 150 K; however the onset of hysteretic magnetization at T = 190 K indicates a transition to an intermediate state lacking long-range order as observed in Nd-227. Our results also show that insulating members of the iridate family have nearly identical magnetic ground states, and that the presence of magnetic A-site species does not play any significant role in altering the ground state properties. 
S. M. Disseler, Chetan Dhital, A. Amato, S. R. Giblin, Clarina de la   Cruz, Stephen D. Wilson, and M. J. Graf
cond-mat.str-el