  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.
