Hybrid Improper Ferroelectricity in Columnar (NaY)MₙMₙTi₄O₁₂

We show that cation ordering on A site columns, oppositely displaced via coupling to B site octahedral tilts, results in a polar phase of the columnar perovskite (NaY)MnMnTi4O12. This scheme is similar to hybrid improper ferroelectricity found in layered perovskites, and can be considered a realisation of hybrid improper ferroelectricity in columnar perovskites. The cation ordering is controlled by annealing temperature and when present it also polarises the local dipoles associated with pseudo-Jahn–Teller active Mn2+ ions to establish an additional ferroelectric order out of an otherwise disordered dipolar glass. Below TN≈12 K, Mn2+ spins order, making the columnar perovskites rare systems in which ordered electric and magnetic dipoles may reside on the same transition metal sublattice

Mechanochemical synthesis of cobalt/copper fluorophosphate generates a multifunctional electrocatalyst

International audienceA mechanochemical synthesis was developed to generate a highly active electrocatalyst featuring catalytic cobalt sites embedded within an electron-withdrawing fluorophosphate host

Low temperature synthesis, structure and magnetic properties of Mn2[VO4]F

The compound Mn2[VO4]F was synthesized using a hydrothermal synthesis route at low temperature and its crystal structure was determined from single crystal X-ray diffraction data. Mn2[VO4]F was characterized by magnetic susceptibility and specific heat capacity measurements. Mn2[VO4]F crystallizes with the triplite-type structure, space group C2/c, a = 13.451(3) Å, b = 6.6953(16) Å, c = 10.126(3) Å, β = 116.587(4)°, V = 815.6(3) Å3 and Z = 8. The structure consists of a 3D-framework built up of VO4 tetrahedra, and manganese (II) polyhedra which form chains running along the [101] and [010] directions. The coordination of the manganese cations and the connectivity between the manganese polyhedra are not defined clearly due to the disorder of the fluoride anions which form zigzag chains along [001]. The magnetic susceptibility follows a Curie–Weiss behavior above 50 K with Θ = −88 K indicating that predominant magnetic interactions are antiferromagnetic. The specific heat capacity and magnetization measurements show that Mn2[VO4]F undergoes a three-dimensional magnetic ordering at TN = 30 K and a canted weak ferromagnetism due to mixed-anion effect