Electronic structures and low-dimensional magnetic properties of the ordered rocksalt oxides Na3Cu2SbO6 and Na2Cu2TeO6

Abstract

The ordered rocksalt-type oxide ${\mathrm{Na}}_3{\mathrm{Cu}}_2\mathrm{Sb}{\mathrm{O}}_6$ was synthesized and its magnetic properties were investigated. The broad peak in the temperature-dependent magnetic susceptibility data near $92\mathrm{K}$ is indicative of the dominant low-dimensional short-range antiferromagnetic (AF) behavior. The data are very well fitted with the AF-AF alternating linear chain model with $J_1∕k=-79\mathrm{K}$ and $J_2∕J_1=0.39$. The high-temperature data $(T>300\mathrm{K})$ exhibit Curie-Weiss behavior with a Weiss temperature of $-55\left(2\right)\mathrm{K}$. These results are very similar to those reported for the isostructural oxide ${\mathrm{Na}}_2{\mathrm{Cu}}_2\mathrm{Te}{\mathrm{O}}_6$ [J. Xu et al., Inorg. Chem. 44, 5042 (2005)]. Recently, it was shown [Y. Miura et al., J. Phys. Soc. Jpn. 75, 847071 (2006)] that an AF-ferromagnetic (F) linear chain model gives an equally good fit to the low-temperature data for both compounds and that further analysis of magnetic heat capacity data supports the AF-F model. We reinvestigate this proposal by computing the intersite hopping integrals using both the tight-binding spin dimer analysis and the $N^{\text{th}}$-order muffin-tin-orbital downfolding procedure for both compounds. The calculations support the AF-AF model for the antimonide. Further, the Weiss temperatures derived from the high-temperature experimental data, $T>300\mathrm{K}$, are also consistent with the $J$ values derived from the AF-AF model but not with those obtained from the AF-F alternative.