Evolution of Magnetism in the Na3-δ(Na1-xMgx)Ir2O6 Series of Honeycomb Iridates
David C. Wallace, Craig Brown, Tyrel M. McQueen
The structural and magnetic properties of a new series of iridium-based honeycomb lattices with the formula Na3-δ(Nad1-x^Mgx)Ir2O6(0less than or equal to}xless than or equal to}) 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 the average Ir-O-Ir bond angle. Samples with x or δ> 0 do not show long range antiferromagnetic order above T=2.0 K, and instead exhibit glassy magnetism with freezing temperatures, Tf, ranging from 3.9 K to 5 K. We further show that the oxidation state of Ir is variable in honeycomb iridates, and samples with imperfect stoichiometry can have significant quantities of low spin d6Ir3+. These magnetic "holes" are likely the origin of the spin glass-like state observed in these and related iridates. Stacking faults between adjacent two dimensional honeycomb layers occur with significant frequency, but have little effect on the magnetic properties. Together, these results demonstrate that chemical defects and non-stoichiometry have a significant effect on the magnetism of compounds in the A2IrO3 materials family.
, Brown, C.
and McQueen, T.
Evolution of Magnetism in the Na<sub>3-δ</sub>(Na<sub>1-x</sub>Mg<sub>x</sub>)Ir<sub>2</sub>O<sub>6</sub> Series of Honeycomb Iridates, Journal of Solid State Chemistry, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915419
(Accessed June 9, 2023)