High temperature ferromagnetism of Li-doped vanadium oxide nanotubes
| Autor: | 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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| Rok vydání: | 2009 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1209/0295-5075/88/57002 |
| Popis: | 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. Comment: with some amendments published in Europhysics Letters (EPL) 88 (2009) 57002; http://epljournal.edpsciences.org |
| Databáze: | arXiv |
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