Synthesis, Structure, and Compositional Tuning of the Layered Oxide Tellurides Sr₂MnO₂Cu_2–xTe₂ and Sr₂CoO₂Cu₂Te₂

Abstract

The synthesis and structure of two new transition metal oxide tellurides, Sr 2 MnO 2 Cu 1.82(2) Te 2 and Sr 2 CoO 2 Cu 2 Te 2 , are reported. Sr 2 CoO 2 Cu 2 Te 2 with the purely divalent Co 2+ ion in the oxide layers has magnetic ordering based on antiferromagnetic interactions between nearest neighbors and appears to be inert to attempted topotactic oxidation by partial removal of the Cu ions. In contrast, the Mn analogue with the more oxidizable transition metal ion has a 9(1)% Cu deficiency in the telluride layer when synthesized at high temperatures, corresponding to a Mn oxidation state of +2.18(2), and neutron powder diffraction revealed the presence of a sole highly asymmetric Warren-type magnetic peak, characteristic of magnetic ordering that is highly two-dimensional and not fully developed over a long range. Topotactic oxidation by the chemical deintercalation of further copper using a solution of I 2 in acetonitrile offers control over the Mn oxidation state and, hence, the magnetic ordering: oxidation yielded Sr 2 MnO 2 Cu 1.58(2) Te 2 (Mn oxidation state of +2.42(2)) in which ferromagnetic interactions between Mn ions result from Mn 2+/3+ mixed valence, resulting in a long-range-ordered A-type antiferromagnet with ferromagnetic MnO 2 layers coupled antiferromagnetically. Figure 1. Crystal structure of Sr 2 MO 2 Cu 2 Te 2 , M = Mn, Co with the detail of the distended coordination environment of the transition metal ion shown. Article pubs.acs.org/IC Cite This: Inorg. Chem. 2019, 58, 8140−8150

Hydroxide-Enhanced Superexchange Magnetic Couplings in Ionic Clathrate Hydrates

“…However, it is noteworthy that the partial p state level of host O falls in the same energy range as the guest O p, which can enhance the interaction between the host–guest and in turn affect the magnetic coupling. In Figure c, we also show a plot of the partial charge density of guest O 2 in these O 2 ·X@CHs, which indicates that those states of host O have the delocalized character and exhibit the p-orbital mixing between paramagnetic guest O 2 via host O in O 2 ·EMN + @CHs. , …”

“…Such an AFM coupling is found to be energetically favorable compared with the case of parallel alignment for O 2 ·EMN + @CHs. Similar to the Goodenough–Kanamori rule for the ligand-mediated superexchange interaction where if two cations with half-filled orbitals overlap with the same p-orbital of a ligand, superexchange interaction between them is AFM. , …”

Effect of Nonmagnetic Ion Deficiency on Magnetic Structure: Density Functional Study of Sr2MnO2Cu2–xTe2, Sr2MO2Cu2Te2 (M = Co, Mn), and the Oxide-Hydrides Sr2VO3H, Sr3V2O5H2, and SrVO2H

“…Our DFT+U+SOC calculations show that the Co 2+ ions of Sr 2 CoO 2 Cu 2 Te 2 prefer the ⊥z direction (Table 2), which agrees with experiment. 7 The PDOS plots calculated for the d-states of Co in Sr 2 CoO 2 Cu 2 Te 2 , presented in Figure 5 2). Given the electron counting d 5 , the high-spin Mn 2+ ion has S = 5/2 and, hence, behaves like a classical spin.…”

“…It is the structure of the 10% Mn−O bond contraction that predicts a FM-coupled MnO 2 Te 2 layer in agreement with experiment. 7 Hereafter, our discussion will be based on the results obtained for the structure with 10% Mn− O bond contraction. The Mn 2+ -O•••O-Mn 2+ exchange J 2 and the Mn 3+ -O•••O-Mn 3+ exchange J 3 are both AFM, but J 3 is stronger than J 2 .…”

“…8 In Sr 2 MnO 2 Cu 1.58 Te 2 , however, the spins of each MnO 2 Te 2 layer are FM-coupled as if the Mn−O−Mn spin exchange is FM in spite of their linear Mn−O−Mn linkages, and they adopt the ||z spin orientation. 7 Thus, the magnetic structure of the MnO 2 Te 2 layer is apparently unusual, in sharp contrast to that of the CoO 2 Te 2 layer. This difference in the magnetic structures of the two layers is caused most likely by the occupancy differences at the nonmagnetic Cu + (d 10 , S = 0) sites (Figure S1).…”