Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 3: Spin-Systeme und itinerante Magnete
TT 3.11: Vortrag
Montag, 8. März 2004, 12:00–12:15, H18
ESR study of the low-dimensional quantum spin system TiOCl — •V. Kataev1,2, J. Baier2, A. Möller3, L. Jongen3, G. Meyer3 und A. Freimuth2 — 1Leibniz-Institut für Festkörper- und Werkstoffforschung PF D-01171 Dresden — 2II. Physikalisches Institut, Universität zu Köln, D-50937 Köln — 3Institut für Anorganische Chemie, Universität zu Köln, D-50939 Köln
We present electron spin resonance (ESR) measurements of Ti3+ (3d1) ions in single crystals of the novel layered quantum spin magnet TiOCl [1]. The ESR data give evidence that the single electron in the d-shell occupies predominantly the dxy orbital which lies in the bc crystallographic plane. This result suggests a formation of a spin-1/2 chain along the b direction, owing to the overlap of the orbital states, and supports recent LDA+U calculations of the band structure [2]. The ESR signal vanishes at Tc=67 K signalling the transition to a non-magnetic, possibly a spin-Peierls state, as proposed in Ref. [2]. Our x-ray powder diffraction data give however no evidence for the structural transition associated with the spin-gap transition. A pronounced dependence of the linewidth and the g factor on temperature suggests a strong coupling of spins to the lattice which may be decisive for the magnetic properties of TiOCl. In connection with the peculiar temperature dependence of the ESR parameters we discuss the role of spin and probably also orbital fluctuations above Tc for the opening of the spin gap.
[1] For details see, V. Kataev et al., Phys. Rev. B 68, 140405(R) (2003).
[2] A. Seidel et al., Phys. Rev. B 67, 020405(R) (2003).
supported by DFG through SFB 608