Synthesis of Four Isomeric Phases of CdVO(SeO₃)₂ and Characterization of Their Structural, Thermal, and Magnetic Properties

We prepared four isomeric phases of CdVO(SeO₃)₂, α-, β-, γ-, and δ-phases by hydrothermal reactions and characterized their structural, thermal, and magnetic properties. These compounds all exhibit one-dimensional (1D) chains made up of distorted VO₅ square pyramids such that the apical oxygen O_ap of each VO₅ square pyramid acts as the sixth ligand to an adjacent VO₅ square pyramid to form the (V-O_ap···V-O_ap···)_∞ chains. The Se⁴⁺ ions of the (SeO₃)^2- anions bridge the basal oxygen atoms O_bs of adjacent VO₅ square pyramids to form the V-O_bs···Se⁴⁺·· O_bs-V spin exchange paths within each (V-O_ap···V-O_ap···)_∞ chain in the γ- and δ-phases, but between the adjacent (V-O_ap···V-O_ap···)_∞ chains in the α- and β<i>-</i>phases. The magnetic properties of the γ- and δ-phases are all described by a 1D antiferromagnetic (AFM) chain model. Surprisingly, so are the magnetic properties of the α- and β-phases because the V-O_bs···Se⁴⁺·· O_bs-V spin exchanges between the adjacent (V-O_ap···V-O_ap···)_∞ chains are substantial only in one direction. The α-, β<i>-</i>, and γ-phases undergo a long-range antiferromagnetic ordering at 3.2 K, 3.5 K, and 2.9 K, respectively, while the δ-phase exhibits paramagnetic behavior down to 2 K.