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TT: Fachverband Tiefe Temperaturen
TT 32: Correlated Electrons: Poster Session
TT 32.57: Poster
Thursday, February 28, 2008, 14:00–18:00, Poster B
Electrochemical doping of Vanadium Oxide Nanotubes — •A. Popa1, I. Hellmann1, R. Klingeler1, V. Kataev1, E. Vavilova1,2, Y. Arango1, C. Täschner1, M. Knupfer1, H.-H. Klauß3, C. Masquelier4, and B. Büchner1 — 1Leibniz-Institute for Solid State and Materials Research IFW Dresden, Germany — 2Kazan Physical Technical Institute, RAS, Kazan, Russia — 3Technical University- Dresden,Germany — 4Laboratoire de Réactivité et de Chimie des Solides, Amiens, France
A new class of nanoscale low-dimensional magnets, mixed valent vanadium oxide multiwall nanotubes (VOx-NTs), show up diverse novel properties ranging from spin frustration and semiconductivity to ferromagnetism by doping with either electrons or holes. The structural low dimensionality and mixed valency of vanadium ions yield a complex temperature dependence of the static magnetization and the nuclear relaxation rates. Upon electron doping of VOx-NTs, our spectroscopic data confirm an increased number of magnetic V4.4+ sites. Interestingly, a considerable superparamagnetic moment of 0.1µ B is found at room temperature after electrochemical intercalation of 10% of Li while no strong effect on the magnetization occurs for other doping levels. Recent µSR studies on Li0.1VOx-NT indeed confirm that more than 40% of the sample is magnetic. This result is corroborated by Li7-NMR measurements which confirm the increase of V4.4+ sites upon Li doping and imply an additional internal magnetic field only for the doping level 0.1.