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

The ordered rocksalt-type oxide Na₃Cu₂SbO₆ was synthesized and its magnetic properties were investigated. The broad peak in the temperature-dependent magnetic susceptibility data near 92 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 J₁∕k=−79 K and J₂∕J₁=0.39. The high-temperature data (T>300 K) exhibit Curie-Weiss behavior with a Weiss temperature of −55(2) K. These results are very similar to those reported for the isostructural oxide Na₂Cu₂TeO₆ [ 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^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 K, are also consistent with the J values derived from the AF-AF model but not with those obtained from the AF-F alternative.