Synthesis and Physical Properties of the Oxofluoride Cu₂(SeO₃)F₂

Abstract

Single crystals of the new compound Cu(SeO)F were successfully synthesized via a hydrothermal method, and the crystal structure was determined from single-crystal X-ray diffraction data. The compound crystallizes in the orthorhombic space group Pnma with the unit cell parameters a = 7.066(4) Å, b = 9.590(4) Å, and c = 5.563(3) Å. Cu(SeO)F is isostructural with the previously described compounds CoTeOF and CoSeOF. The crystal structure comprises a framework of corner- and edge-sharing distorted [CuOF] octahedra, within which [SeO] trigonal pyramids are present in voids and are connected to [CuOF] octahedra by corner sharing. The presence of a single local environment in both the F andSe solid-state MAS NMR spectra supports the hypothesis that O and F do not mix at the same crystallographic positions. Also the specific phonon modes observed with Raman scattering support the coordination around the cations. At high temperatures the magnetic susceptibility follows the Curie-Weiss law with Curie temperature of Θ = -173(2) K and an effective magnetic moment of μ ∼ 2.2 μ. Antiferromagnetic ordering below ∼44 K is indicated by a peak in the magnetic susceptibility. A second though smaller peak at ∼16 K is tentatively ascribed to a magnetic reorientation transition. Both transitions are also confirmed by heat capacity measurements. Raman scattering experiments propose a structural phase instability in the temperature range 6-50 K based on phonon anomalies. Further changes in the Raman shift of modes at ∼46 K and ∼16 K arise from transitions of the magnetic lattice in accordance with the susceptibility and heat capacity measurements.

S = 1/2 Chain in BiVO3F: Spin Dimers versus Photoanodic Properties

“…BiVO3F offers a unique opportunity to examine the magnetic M-O-M versus M-F-M superexchange in a single material, without of the engagement of oxygen ions incounter polyanions on the oxygen mediating corner, such as PO4, SeO3 and TeO3 in the compounds mentioned above. [19][20][21][22] Here the octahedral distortion due to the V=O vanadyl bond externally to the chain-…”

Proton-detected fast-magic-angle spinning NMR of paramagnetic inorganic solids

“…This is provided by a 2D sideband separation experiment such as the adiabatic Magic Angle Turning (aMAT) sequence, 14 which uses a train of adiabatic refocusing pulses 46 with unique timings in order to result in pure isotropic evolution in the indirect dimension. The experiment, originally developed for lower-g nuclei in the context of energy storage materials, [47][48][49][50] achieves a 2D spectrum correlating pure isotropic to anisotropic frequencies (Fig. 1d), with a projection along the indirect dimension (Fig.…”

Cycloidal Magnetic Order Promoted by Labile Mixed Anionic Paths in M2(SeO3)F2 (M = Mn2+, Ni2+)

“…Cu, Mn and X = Te, Se). 4,5,10 Note that our single crystal XRD data allows for a more accurate structural model than reported for the Mn and Ni compounds necessary for the DFT calculations initiated later. A significant but isotropic contraction of all lattice parameters by 5% occurs for Ni2(SeO3)F2 related to the Mn 2+ vs. Ni 2+ relative ionic radii, which highlights the three-dimensional (3D) character of the framework.…”

“…2 On the other hand, the smaller fluoride anion may act as a bridging species between transition metal cations forming there by sizeable dimensionalities in phases such as the 1D-Fe(SeO3)F 3 , or the 3D-M2(SeO3)F2 (M = Co, Cu). 4,5 Here, the contrasting magnetic exchanges mediated by O 2-vs. Fmay procure a playground for destabilizing the standard collinear spin order into exotic ones, and provide a nice platform for spin-induced multiferroicity.…”