In this study, we performed powder neutron diffraction and inelastic scattering measurements of frustrated pyrochlore Nd$_2$Ir$_2$O$_7$, which exhibits a metal-insulator transition at a temperature $T_{rm MI}$ of 33 K. The diffraction measurements re
vealed that the pyrochlore has an antiferromagnetic long-range structure with propagation vector $vec{q}_{0}$ of (0,0,0) and that it grows with decreasing temperature below 15 K. This structure was analyzed to be of the all-in all-out type, consisting of highly anisotropic Nd$^{3+}$ magnetic moments of magnitude $2.3pm0.4$$mu_{rm B}$, where $mu_{rm B}$ is the Bohr magneton. The inelastic scattering measurements revealed that the Kramers ground doublet of Nd$^{3+}$ splits below $T_{rm MI}$. This suggests the appearance of a static internal magnetic field at the Nd sites, which probably originates from a magnetic order consisting of Ir$^{4+}$ magnetic moments. Here, we discuss a magnetic structure model for the Ir order and the relation of the order to the metal-insulator transition in terms of frustration.
