Iridium oxides are of interest because many novel magnetic phases have been predicted in crystals, depending on the geometry of the crystal lattice. Our proposal concerns one such iridium oxide, Yb2Ir2O7, having a crystal structure known as the pyrochlore structure, in which the Ir ions form networks of connected tetrahedra. Our aim is to use neutron diffraction to determine the magnetic structures that occurs in these materials at low temperatures. In a previous experiment we determined that the iridium magnetic moments point either all in or all out of the tetrahedral, which means it is possible that iridates in this family could exhibit a novel topological phase called a Weyl semi-metal. In this proposal our focus is on the Yb moments. We wish to find out how they order at very low temperature, and how this order couples to the iridium magnetic moments.