Synthesis, Crystal Structure, and Physical Properties of BaAg₂Cu[VO₄]₂: A New Member of the S = ¹/₂ Triangular Lattice

Abstract

By application of flux growth methods in combination with redox reactions, single crystals of BaAg(2)Cu[VO(4)](2) can be synthesized. A new structure type (triclinic, P1, Z = 2, a = 5.448(2) Å, b = 5.632(3) Å, c = 14.393(6) Å, α = 94.038(9)°, β = 90.347(6)°, and γ = 118.195(5)°) has been found and will be described here. Structure-properties relationships have been investigated by spectroscopic methods (IR, UV-vis-NIR, ESR) and the electronic structure will be discussed within the angular-overlap model (AOM) for Cu(2+). Furthermore, we present the magnetization and specific heat data for BaAg(2)Cu[VO(4)](2) representing a Heisenberg spin system with exclusive super-super exchange (SSE) on a frustrated magnetic triangular lattice. Considerable antiferromagnetic (AFM) low-dimensional interaction is evident, and ferromagnetic-like long-range order sets in at ≈0.7 K.

Hydrothermal synthesis of single crystals of transition metal vanadates in the glaserite phase

“…[17] Appropriately it is named after Christopher Glaser, perhaps the first practicing descriptive inorganic chemist. [18] It has an enormous range of derivatives, [19] whereby the potassium site can range from alkali to alkaline earth ions, [20] the sodium site can be occupied by metals ranging from transition metals [21] to rare earths in a variety of oxidation states, [22] and the tetrahedral building block can be virtually any known tetrahedron including phosphates, vanadates, [14,23,24] chromates, [17] ruthenates [25] and silicates. [26] As such the phase behaves as a highly adaptive solid-state structure.…”

“…These structures are shown inFigure 4. It should be noted that even in the distorted structures the general triangular lattice is maintained, making all interesting candidates for further magnetic studies [23,28,29].…”

AAg2M[VO4]2Möller1, Amuneke2, Daniel3 et al. 2012Phys. Rev. BSelf Cite381480View full textAdd to dashboardCite

“…Extended microscopic calculations have revealed a competition between AFM (due to virtual elec- tron hopping) and FM (Hund's rule coupling) interactions. 20 Changing the dihedral angle mainly tunes the AFM coupling and affects the effective exchange interaction that can eventually give rise to magnetic orders at low temperature. It seems conceivable to assume that the compression of the in-plane lattice constants results in a change (possibly increase) of some dihedral angles and an enhancement of the FM correlations.…”

“…19 This may lead to counterintuitive results originating from the presence of ferromagnetic (FM) and antiferromagnetic (AFM) coupled S = 1/2 chains, as was recently discussed for BaAg 2 Cu[VO 4 ] 2 . 20,21 These considerations have motivated us to target a 2D model system with the motif of a triangular lattice of magnetic 3d transition metal ions exclusively bridged by nonmagnetic linkers, AAg 2 M[VO 4 ] 2 , with A 2+ = Sr or Ba and M 2+ = Co, Ni, Mg. The two former transition metal ions are magnetic and represent the spin systems of S = 3/2 and 1, respectively.…”

Re-entrant spin glass and stepped magnetization in mixed-valence SrFe3(PO4)3

“…The PO 4 anion groups can mediate a competition between Fe-O-Fe superexchange (SE) and Fe-O-O-Fe supersuperexchange (SSE) interactions. The SSE interaction is often underestimated but strong in some S¼1/2 systems [16,17]. The sign and magnitude of SE interaction can be predicated by semiempirical Goodenough-Kanamori-Anderson rules, which is useful to determine the sign of superexchange interactions by both occupied orbitals of adjacent Fe atoms and geometrical information (bond angles and lengths) of Fe-O-Fe [18].…”