DPG Phi
Verhandlungen
Verhandlungen
DPG

Regensburg 2007 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons - Poster Session

TT 20.33: Poster

Wednesday, March 28, 2007, 14:00–17:45, Poster A

Electrochemical doping of Vanadium Oxide Nanotubes — •A. Popa1, I. Hellmann1, R. Klingeler1, V. Kataev1, E. Vavilova1,2, Y. Arango1, C. Täschner1, X. Liu1, M. Knupfer1, C. Masquelier3, and B. Büchner11Leibniz-Institute for Solid State and Materials Research IFW Dresden, Dresden, Germany — 2Kazan Physical Technical Institute, RAS, Kazan, Russia — 3Laboratoire de Réactivité et de Chimie des Solides, Amiens, France

Vanadium oxide nanotubes (VOx-NTs) exhibit diverse properties ranging from spin frustration and semiconductivity to ferromagnetism by doping with either electrons or holes [1]. We have applied optical, photoemission and EELS as well as static magnetization, ESR and NMR studies in order to obtain insight into the rich physics of these materials. Our data suggest an averaged vanadium valency of about 4.4+ in the undoped case [2]. We observe two magnetically nonequivalent vanadium sites, attributed to V4+ ions (3d1, S=1/2) in octahedral and tetrahedral oxygen coordination and there are strong indications that antiferromagnetic dimers and trimers occur in the vanadium-spin chains in the walls. We find a spin gap of the order of 700 K [3]. Upon electron doping of VOx-NTs, our spectroscopic data confirm a higher number of magnetic V4+ sites. Besides, the magnetic response was studied after the electrochemical insertion of lithium. For certain doping levels, a ferromagnetic signal at room temperature was found.
[1] L. Krusin-Elbaum et al., Nature 431, 672 (2004)
[2] X. Liu et al., Phys. Rev. B 72, 115407 (2005)
[3] E. Vavilova et al., Phys Rev. B 73, 144417 (2006)

100% | Mobile Layout | Deutsche Version | Contact/Imprint/Privacy
DPG-Physik > DPG-Verhandlungen > 2007 > Regensburg