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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 6.32: Poster
Monday, March 26, 2001, 14:30–17:00, Rang S\ 3
NMR investigation of pure and doped NaV2O5 — •Rudi Michalak, Matthias Dischner, Husam Mohammad, Christoph Geibel, and Frank Steglich — Max Planck Institut für chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187 Dresden
Sodium vanadate, NaV2O5, is a low dimensional magnetic system that displays a double phase transition of about 34 K. It is currently believed that, below the transition temperature, sodium vanadate exhibits charge ordering and spin-Peierls dimerisation. To date, the relationship between the two transitions remains unclear. [1] have recently shown by specific heat measurements that isoelectronic doping of the sodium site with Li, or doping with higher valent Ca, both rapidly suppresses the transition temperature. The details of the suppressions, however, are quite different. Here, we present first 23Na and 51V NMR data on the pure compound and on a series of Li- and Ca- doped single crystal samples . This method provides microscopic access to the various doping induced sites. We have studied in detail the appearance of the valence-change induced split of the vanadium signals at a characteristic temperature and their doping dependence. We find that the valence split may occur at higher temperatures in the undoped compound than has previously been assumed. In addition, below the transition temperature we studied the doping dependence of the split of the sodium lines. We found up to eight separate sites signals. This is in agreement with a recent claim claimed by [2] for the undoped material.
[1] M.Dischner et al., JMMM in print [2] Y. Fagot-Revurat et al., Phys.Rev.Lett. 84, 4176, 2000