Rubidium vanadium(<scp>iii</scp>) vanadyl(<scp>iv</scp>) phosphate, Rb₃V³⁺(V⁴⁺O)(PO₄)(H_0.5PO₄)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 <i>P</i>1̄ with the unit cell parameters <i>a</i> = 9.637(1), <i>b</i> = 12.254(2), <i>c</i> = 12.336(2) Å, <i>α</i> = 105.82(1), <i>β</i> = 104.81(1) and <i>γ</i> = 102.75(1)°. Its crystal structure was determined by single crystal X-ray diffraction. The structure of Rb₃V³⁺(V⁴⁺O)(PO₄)(H_0.5PO₄)₂ is formed from V³⁺-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 <i>via</i> V⁴⁺O₅ polyhedra in a three-periodic framework with channels running parallel to the <i>a</i> and <i>b</i> axes. Rb atoms occupy positions inside the framework channels. The title compound achieves a long range ordered antiferromagnetic state at <i>T</i>_N = 2.1 K and formally demonstrates a high value of the magnetic frustration parameter <i>f</i> equal to the ratio of the Weiss and Néel temperatures |<i>Θ</i>|/<i>T</i>_N = 15, which can be attributed to the reduced dimensionality of the magnetic subsystem. At <i>T</i> < <i>T</i>_N, the magnetization curve exhibits the signature of the 1/3 plateau.