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.
Highlights
Quantum-spin systems have attracted considerable attention since the discovery of characteristic quantum phenomena such as superconductivity and quantum-spin liquids (Lee, 2008; Balents, 2010)
According to the indices obtained from the powder X-ray diffraction (XRD) patterns, the zone axes of the incident electron beams were identified in the Selected-area electron diffraction (SAED) patterns
Observed the diffraction spots of the 00l condition by tilting the specimen to remove the multiple reflections at forbidden reflection positions, which may appear in a crystal structure with screws or grid planes [Fig. 1(d)]
Summary
Quantum-spin systems have attracted considerable attention since the discovery of characteristic quantum phenomena such as superconductivity and quantum-spin liquids (Lee, 2008; Balents, 2010). Spin dimer systems are representative materials that exhibit quantum-spin fluctuations. In such systems, magnetic ions are often coupled with antiferromagnetic exchange interactions, resulting in the formation of spin dimers. Dimers are coupled with neighbouring dimers via weak exchange interactions. With increasing interactions between dimers in low-dimensional systems, spin dimer compounds can be considered as an alternating chain system. Dimerized quantum magnets usually display an energy gap between spin-singlet non-magnetic ground and triplet excited states; the inter- and intra-dimer interactions caused by the arrangement of magnetic ions affect the energy gap
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