Rubidium vanadium(III) vanadyl(IV) phosphate, Rb 3 V 3+ (V 4+ O)(PO 4 )(H 0.5 PO 4 ) 2 : crystal chemistry and low-dimensional magnetism.

In this paper, we present the synthesis and characterization of a rubidium vanadium(III) vanadyl(IV) phosphate, obtained under hydrothermal conditions. The new compound crystallizes in the triclinic space group P 1̄ with the unit cell parameters a = 9.637(1), b = 12.254(2), c = 12.336(2) Å, α = 105.82(1), β = 104.81(1) and γ = 102.75(1)°. Its crystal structure was determined by single crystal X-ray diffraction. The structure of Rb ₃ V ³⁺ (V ⁴⁺ O)(PO ₄ )(H _0.5 PO ₄ ) ₂ is formed from V ³⁺ -centered octahedra sharing all oxygen vertices and one edge with phosphate tetrahedra to form ribbons parallel to the [011] direction. These ribbons are further linked via V ⁴⁺ O ₅ polyhedra in a three-periodic framework with channels running parallel to the a and b axes. Rb atoms occupy positions inside the framework channels. The title compound achieves a long range ordered antiferromagnetic state at T _N = 2.1 K and formally demonstrates a high value of the magnetic frustration parameter f equal to the ratio of the Weiss and Néel temperatures | Θ |/ T _N = 15, which can be attributed to the reduced dimensionality of the magnetic subsystem. At T < T _N , the magnetization curve exhibits the signature of the 1/3 plateau.