Crystal structure and magnetism in the S = 1/2 spin dimer compound NaCu2VP2O10

Abstract

The crystal structure of the spin dimer magnet NaCu₂VP₂O₁₀ was determined using single-crystal X-ray diffraction and electron diffraction. NaCu₂VP₂O₁₀ displayed a non-centrosymmetric orthorhombic C222₁ structure with a = 6.13860 (10) Å, b = 14.4846 (3) Å and c = 8.2392 (2) Å. The layered structure comprised CuO₄ plaquettes, VO₆ octahedra and PO₄ tetrahedra. A pair of CuO₄ plaquettes formed Cu₂O₆ structural dimers through edge sharing. The Cu-Cu network formed a distorted puckered-layer structure with pseudo-one-dimensional characteristics. Maximum magnetic susceptibility was observed at ∼60 K and NaCu₂VP₂O₁₀ became non-magnetic upon further cooling. The spin gap between the spin-singlet non-magnetic ground state and triplet excited state was estimated to be 43.4 K. Thus, NaCu₂VP₂O₁₀ was assumed to be an alternating chain system with a singlet ground state of dimer origin. The V⁵⁺ ions in the VO₆ octahedra showed large off-centre displacements along the [110] direction in the primitive perovskite structure, which were attributed to the pseudo-Jahn-Teller distortion of d ⁰ transition metals.

Keywords: electron diffraction; magnetic susceptibility; single-crystal X-ray diffraction; spin dimer compounds.