Evolution of magnetism in the Na3−δ(Na1−xMgx)Ir2O6Na3−δ(Na1−xMgx)Ir2O6 series of honeycomb iridates

The structural and magnetic properties of a new series of iridium-based honeycomb lattices with the formula Na3−δ(Na1−xMgx)Ir2O6Na3−δ(Na1−xMgx)Ir2O6(0≤x≤1)(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 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.

The magnetic properties of honeycomb iridates strongly depend on iridium spacing and the concentration of non-magnetic Ir3+ sites.Figure optionsDownload as PowerPoint slide