Synthesis, Structure, and Magnetic Properties of the Layered Copper(II) Oxide Na₂Cu₂TeO₆

Abstract

A new quaternary layered transition-metal oxide, Na2Cu2TeO6, has been synthesized under air using stoichiometric (with respect to the cationic elements) mixtures of Na2CO3, CuO, and TeO2. Na2Cu2TeO6 crystallizes in the monoclinic space group C2/m with a = 5.7059(6) A, b = 8.6751(9) A, c = 5.9380(6) A, beta = 113.740(2) degrees, V = 269.05(5) A3, and Z = 2, as determined by single-crystal X-ray diffraction. The structure is composed of infinity(2)[Cu2TeO6] layers with the Na atoms located in the octahedral voids between the layers. Na2Cu2TeO6 is a green nonmetallic compound, in agreement with the electronic structure calculation and electrical resistance measurement. The magnetic susceptibility shows Curie-Weiss behavior between 300 and 600 K with an effective moment of 1.85(2) muB/Cu(II) and theta(c) = -87(6) K. A broad maximum at 160 K is interpreted as arising from short-range one-dimensional antiferromagnetic correlations. With the aid of the technique of magnetic dimers, the short-range order was analyzed in terms of an alternating chain model, with the surprising result that the stronger intrachain coupling involves a super-superexchange pathway with a Cu-Cu separation of >5 A. The J2/J1 ratio within the alternating chain refined to 0.10(1), and the spin gap is estimated to be 127 K.

Structure and basic magnetic properties of the honeycomb lattice compounds Na2Co2TeO6 and Na3Co2SbO6

“…The bond valence sums are consistent with the assignment of Co 2+ and Te 6+ as formal oxidation states. The two-layer stacking sequence found for Na 2 Co 2 TeO 6 is distinctly different from that found for the Cu analog, Na 2 Cu 2 TeO 6 [17], which, though monoclinic, is based on a pseudo-hexagonal three-layer stacking sequence. Na 3 Co 2 SbO 6 was found to be isostructural with Na 3 Cu 2 SbO 6 .…”

Orbitally induced hierarchy of exchange interactions in the zigzag antiferromagnetic state of honeycomb silver delafossite Ag3Co2SbO6

“…In particular, among the Cu 3 M 2+ 2 SbO 6 series (M = Mn, Co, Ni, Cu), the magnetism of manganese compound was not characterized at all [31]. The honeycomb S=1/2 delafossite compound Cu 5 SbO 6 (Cu + 3 Cu 2+ 2 Sb 5+ O 6 ) was characterized as dimerized system, in which the ground state is a spin singlet [32] similarly to previously known NaFeO 2 -derived Cu 2+ honeycomb compounds Na 2 Cu 2 TeO 6 [33][34][35] and Na 3 Cu 2 SbO 6 [35][36][37][38][39] and in spite of significant structural differences. At the same time both polytypes of Cu 3 Ni 2 SbO 6 and Cu 3 Co 2 SbO 6 compounds were found to order antiferromagnetically with transitions, at 22.3 and 18.5 K for Ni and Co variants, respectively, with Curie−Weiss fits that are in agreement with Ni 2+ and Co 2+ high spins [40,41].…”

Magnetic Excitations of Spin-Gap System Na3Cu2SbO6 with Distorted Honeycomb Structure

“…The neutron measurements were carried out on the triplet-axis-spectrometer ISSP-PONTA at JRR-3 of Japan Atomic Energy Agency in Tokai. Three crystals aligned within 0.7 ° were used, where the typical volume of each crystal was about 60 mm 3 . The 002 reflection of the pyrolytic graphite (PG) was used both for the monochromator and the analyzer.…”