High-temperature ferromagnetism of Li-doped vanadium oxide nanotubes

The nature of a puzzling high-temperature ferromagnetism of doped mixed-valent vanadium oxide nanotubes reported earlier by Krusin-Elbaum et al., Nature, 431 (2004) 672, has been addressed by static magnetization, muon spin relaxation, nuclear magnetic and electron spin resonance spectroscopy techni...

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Veröffentlicht in:Europhysics letters 2009-12, Vol.88 (5), p.57002
Hauptverfasser: Popa, A. I, Vavilova, E, Arango, Y. C, Kataev, V, Täschner, C, Klauss, H.-H, Maeter, H, Luetkens, H, Büchner, B, Klingeler, R
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Sprache:eng
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Zusammenfassung:The nature of a puzzling high-temperature ferromagnetism of doped mixed-valent vanadium oxide nanotubes reported earlier by Krusin-Elbaum et al., Nature, 431 (2004) 672, has been addressed by static magnetization, muon spin relaxation, nuclear magnetic and electron spin resonance spectroscopy techniques. A precise control of the charge doping was achieved by electrochemical Li intercalation. We find that it provides excess electrons, thereby increasing the number of interacting magnetic vanadium sites, and, at a certain doping level, yields a ferromagnetic-like response persisting up to room temperature. Thus we confirm the surprising previous results on the samples prepared by a completely different intercalation method. Moreover our spectroscopic data provide first ample evidence for the bulk nature of the effect. In particular, they enable a conclusion that the Li nucleates superparamagnetic nanosize spin clusters around the intercalation site which are responsible for the unusual high-temperature ferromagnetism of vanadium oxide nanotubes.
ISSN:0295-5075
1286-4854
DOI:10.1209/0295-5075/88/57002