%0 Journal Article %T Evolution of Magnetism in the $Na_{3-d}Na_{1-x}Mg_xIr_2O_6$ Series of Honeycomb Iridates %A D. C. Wallace %A C. M. Brown %A T. M. McQueen %J Physics %D 2014 %I arXiv %R 10.1016/j.jssc.2014.03.013 %X The structural and magnetic properties of a new series of iridium-based honeycomb lattices with the formula Na3-delta(Na1-xMgx)Ir2O6 (x = 0 to 1) are reported. As x and delta are increased, the honeycomb lattice contracts and the strength of the antiferromagnetic interactions decreases systematically due to a reduction in Ir-O-Ir bond angles. Samples with imperfect stoichiometry exhibit disordered magnetic freezing at temperatures Tf between 3.4 K and 5 K. This glassy magnetism likely arises due to the presence of non-magnetic Ir3+, which are distributed randomly throughout the lattice, with a possible additional contribution from stacking faults. Together, these results demonstrate that chemical defects and non-stoichiometry have a significant effect on the magnetism of compounds in the A2IrO3 materials family. %U http://arxiv.org/abs/1404.4579v1