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TT: Tiefe Temperaturen
TT 6: Postersitzung I (Amorphe- u. Tunnelsysteme, Niedrigdimensionale Systeme, Supraleitung: Elektronenstruktur, Phononen, Tunneln, Ordnungsparameter)
TT 6.15: Poster
Monday, March 24, 2003, 14:30–19:00, P2c, P2d
Structural and magnetic properties of a low-dimensional spin magnet InCu2/3V1/3O3 — •V. Kataev1, A Möller2, W Jung2, N Schittner1, M Kriener1, and A Freimuth1 — 1II. Physikalisches Institut, Universität zu Köln — 2Institut für Anorganische Chemie, Universität zu Köln
Polycrystalline samples of InCu2/3V1/3O3 have been obtained from mixtures of In2O3, CuO, V2O5 (molar ratio 3:4:1) at 900 ∘C (5d) under a constant flow of O2 in a Pt crucible. The compound crystallizes in the hexagonal space group P63/mmc, a=3.3564(8) Å and c=11.908(3) Å. Non-magnetic V5+ and magnetic Cu2+ (S=1/2) ions share a common site-set with 5-fold triangular-bipyramidal coordination of oxygen ions which is exceptional for Cu2+. These polyhedra are corner-connected to form hexagonal layers separated by layers of In3+ ions along the c-axis. Measurements of static magnetic susceptibility χ and electron spin resonance (ESR) reveal a strong antiferromagnetic coupling of Cu spins with J∼ 300 K. The compound orders magnetically at 38 K. The T-dependence of χ is reminiscent of low-dimensional spin magnets, suggesting that Cu spins in the hexagonal planes may form e.g. chains or rings. Remarkably, ESR gives evidence that the ground state orbital of Cu2+ is d3z2−r2 and not dx2−y2 as in copper oxides with the usual octahedral, square-pyramidal or square-planar coordination. We discuss the origin of such an unusual orbital state of Cu as well as possible spin arrangements in InCu2/3V1/3O3. supported by DFG through SFB 608