Order-disorder transitions of t2g-orbitals of V3+ ions and incommensurate structural deformations in the metallic spinel CuV2S4

• Published in: Physica Status Solidi (b) 2007-07, Vol.244 (7), p.2565-2575
• Main Authors: Hidaka, M., Tokiwa, N., Wijesundera, R. P., Awaka, J., Nagata, S., Park, Young Jun, Lee, Ki Bong
• Format: Article
• Language: English
• Subjects: 64.70.Kb; 64.70.Rh; 71.45.Lr; 77.80.Bh; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Physics; Structure of solids and liquids; crystallography
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.200642194

Structural transitions of the spinel CuV2S4 have been studied by means of X‐ray diffraction using synchrotron radiation. The temperature dependence of reflections forbidden in a cubic spinel structure of Fd3m suggests that there are order–disorder transitions of 3d2 (t2g) orbitals of V3+ ions at about 75 and 210 K. An incommensurate superlattice reflection of (2+3/4, 2, 2+3/4) shows the structural phase transition occurring at about 90 K, in addition to the superlattice structural modulation at about 30–35 and 55 K. A reduced wavevector q = (3/4–δ, 0, 3/4–δ) shows the temperature dependence of the δ value from 0.015 to –0.025. A lock‐in of δ = 0.0 and a crossover of the δ value occur in the region of 40 to 50 K. The incommensurate structural modulation along [110], [011], and [101] directions appearing below about 90 K affects a paramagnetic spin order of V3+ ions at about 30–35 and 55 K, in addition to the 90 K structural transition. The paramagnetic behavior is interpreted mainly by the structural deformation and the (dxy , dyz , dzx ) orbitals in the VS6 octahedral chains sited along [110], [011], and [101] directions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)