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TT: Tiefe Temperaturen
TT 6: Postersitzung I: Josephsonkontakte und SQUIDs, Supraleitung: Theorie, Korrelierte Elektronen, Niederdimensionale Systeme, Magnetotransport, Quantenhalleffekt, Kohlenstoff-Nanoröhrchen, Quantenflüssigkeiten
TT 6.36: Poster
Montag, 26. März 2001, 14:30–17:00, Rang S\ 3
Sr2V3O9 and Ba2V3O9: Spin chains with strong Dzyaloshinsky-Moriya interaction — •Enrique Kaul1, Roman Shpanchenko2, Jörg Sichelschmidt1, and Cristoph Geibel1 — 1Max-Planck Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden, Germany — 2Moscow State University, Dep. of Chemistry, Moscow 119899, Russia
Sr2V3O9 and Ba2V3O9 are materials with low dimensional structures formed by chain-like arrangements of S=1/2 V+4 octahedra. Sr2V3O9 has corner-sharing chains which are linked by V+5 tetrahedra forming 2D layers. Ba2V3O9 has rutyle-like chains of edge-sharing V+4 octahedra. We synthesized pure polycrystalline Sr2V3O9 and Ba2V3O9 by the solid state reaction method and performed specific heat Cp(T), magnetic susceptibility χ(T) and ESR measurements. χ(T) presents in both compounds a maximum at 50K (Sr2V3O9) and 60K (Ba2V3O9) evidencing low dimensional magnetic interactions. Fitting χ(T) with the Bonner-Fisher model lead to an intrachain interaction exchange J=78K (Sr2V3O9) and J=97K (Ba2V3O9). This is confirmed by a corresponding linear term in the specific heat at low temperatures. χ(T), Cp(T) and ESR results clearly indicate magnetic order near 5K in Sr2V3O9, whereas no evidence of magnetic order was found in Ba2V3O9 down to 0.5K. This indicate a stronger interchain coupling in Sr2V3O9 than in Ba2V3O9, as expected from the structure. The presence of systematic upturns in the χ(T) at low temperatures in both compounds suggest the presence of a strong Dzyaloshinsky-Moriya interaction.