  Electron correlation strength is predicted to be weak in 5d transition metal
oxides and hence, various anomalous electronic properties observed in these
systems are often attributed to the large spin-orbit interaction strength.
Employing first principles approaches, we studied the electronic structure of
Y2Ir2O7, which is insulating and exhibits ferromagnetic phase below 150 K. The
results reveal breakdown of both the above paradigms. The role of spin-orbit
interaction is found to be marginal in determining the ground state properties
of Y2Ir2O7. A large electron correlation strength is required to derive the
experimental bulk spectrum that is consistent with the bulk properties.
