PbMnTeO₆: a chiral quasi 2D magnet with all cations in octahedral coordination and the space group problem of trigonal layered A²⁺M⁴⁺TeO₆

Abstract

Neutron diffraction rejects the prismatic P6̄2m model with Mn/Te disorder and proves the chiral structure with octahedral coordination for all cations.

Triangular Magnet Emergent from Noncentrosymmetric Sr0.94Mn0.86Te1.14O6 Single Crystals

“…To provide charge balance, there should be 0.16Mn 3+ and 0.70Mn 4+ , resulting in 3.81 as average oxidation number of Mn. It should be noted that the resultant “partially ordered” structure is consistent with previously reported PbMnTeO 6 …”

“…This was extremely strange for Mn 4+ and Te 6+ and was never found for these small cations among hundreds of studied structures . Later, this structure for PbMnTeO 6 was corrected to be P 312, and we expected the same for SrMnTeO 6 .…”

“…It should be noted that the resultant "partially ordered" structure is consistent with previously reported PbMnTeO 6 . 17 The diffraction pattern of the flat single crystals shows (00l) reflections (Figure 1b), indicating that the geometric hexagonal shape is preferably along the ab-plane. The morphology and optical image of the SMTO crystal are shown in the insets of Figure 1a,b, respectively.…”

“…This results in doubling the cell edge c but the structure retains the inversion center, space group being P 31̅ c (or P 2 1 / c for BiMnTeO 6 , distorted by the Jahn–Teller effect). On the other hand, in AGeTeO 6 (A = Sr, Mn, Cd, or Pb), PbMnTeO 6 , and BiMTeO 6 (M = Al and Ga), M/Te only order within the honeycomb layer without changing cell volume, thus eliminating mirror plane and inversion center (chiral space group P 312). BaGeTeO 6 belongs to the same space group but has doubled a cell edge c because of the different oxygen stacking (ABBA vs ABAB) and prismatic (rather than antiprismatic) coordination of Ba 2+ .…”

Successive short- and long-range magnetic ordering in rosiaite-type CoGeTeO6 prepared by ion-exchange reaction

“…Similar structures were also formed with heterovalent combinations of (M′ 4+ , Te 6+ ) (M′ = Mn, Ge, Sn) in place of two Sb 5+ ions, i.e. , PbMnTeO 6 , 11,12 “SrMnTeO 6 ” (actually nonstoichiometric), 13 MGeTeO 6 (M = Mn, Cd, Pb), 14 and MnSnTeO 6 . 15 One more type of rosiaite-related phase has the formula R 3+ M 3+ TeO 6 , where R = rare earth or Bi, and M = Cr, Mn or Fe.…”