Evolution of magnetism in the [formula omitted] series of honeycomb iridates.

The structural and magnetic properties of a new series of iridium-based honeycomb lattices with the formula Na 3 − δ ( Na 1 − x Mg x ) Ir 2 O 6 ( 0 ≤ x ≤ 1 ) are reported. As x and δ 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 T f between 3.4 K and 5 K. This glassy magnetism likely arises due to the presence of non-magnetic Ir 3+ , 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 A 2 IrO 3 materials family. [ABSTRACT FROM AUTHOR]