Berlin 2008 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 32: Correlated Electrons: Poster Session
TT 32.58: Poster
Thursday, February 28, 2008, 14:00–18:00, Poster B
Investigations on oxide nanocompounds — •Ingo Hellmann1, Andreia Popa1, Yulieth Arango1, Evgenia Vavilova1,2, Anupama Parameswaran1, Rüdiger Klingeler1, Vladislav Kataev1, Galina Zakharova3, Christine Täschner1, Martin Knupfer1, and Bernd Büchner1 — 1IFW Dresden, Dresden, Germany — 2Kazan Physical Technical Institute, Kazan, Russia — 3Institute of Solid State Chemistry, Yekaterinburg, Russia
In transition metal oxide nanocompounds the small size of these structures as well as charge, spin and orbital degrees of freedom of the 3d-ions lead to properties which can be quite different from the respective bulk materials. We applied optical spectroscopy, PES and EELS as well as static magnetization, ESR and NMR studies in order to obtain insight into the rich physics of these materials. Vanadium oxide nanotubes exhibit diverse properties ranging from spin frustration and semiconductivity to superparamagnetism or even ferromagnetism by Li-doping. The intercalation of a small amount of other ions, such as Co, Fe, Mn, Cr, strongly affects the magnetic and electronic characteristics. As an example, Co0.18V2O5 nanotubes show antiferromagnetic ordering at 15 K. Interestingly, a ferromagnetic hysteresis is observed at still lower temperatures. A similar magnetic response was obtained for α-MnO2 nanorods which consist of edge coupled octahedra forming tunnel-like structures. The Mn-ion is present in a 4+ oxidation state with spin S = 3/2. By electron doping via an electrochemical reaction or in-situ evaporation using lithium, the manganese valency can be tuned in order to obtain Mn3+ sites having spin S = 2.