Order–disorder transitions of t 2g ‐orbitals of V 3+ ions and incommensurate structural deformations in the metallic spinel CuV 2 S 4

• Published in: physica status solidi (b) Vol. 244; no. 7; pp. 2565 - 2575
• Main Authors: Hidaka, M., Tokiwa, N., Wijesundera, R. P., Awaka, J., Nagata, S., Park, Young Jun, Lee, Ki Bong
• Format: Journal Article
• Language: English
• Published: 01.07.2007
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.200642194

Abstract Structural transitions of the spinel CuV 2 S 4 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 3d 2 (t 2g ) orbitals of V 3+ 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 V 3+ 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 (d xy , d yz , d zx ) orbitals in the VS 6 octahedral chains sited along [110], [011], and [101] directions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)