Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 20: Correlated Electrons - Poster Session
TT 20.30: Poster
Mittwoch, 28. März 2007, 14:00–17:45, Poster A
7Li NMR and ESR study of the Cu spin dynamics and Li mobility in the frustrated spin-1/2 chain cuprate Li2ZrCuO4 — •Y. Arango1, E. Vavilova1,2, V. Kataev1,2, S.-L. Drechsler1, A. Moskvin3, O. Volkova1,4, A. Vasilyev4, and B. Büchner1 — 1Institute for Solid State and Materials Research IFW Dresden, D-01171 Dresden, Germany — 2Kazan Physical Technical Institute of RAS, 420029 Kazan, Russia — 3Ural State University, 620083 Ekaterinburg, Russia — 4Moscow State University, 119992 Moscow, Russia
The new frustrated quasi-1D quantum spin system Li2ZrCuO4 is close to a ferromagnetic critical point and exhibits unusual thermodynamic properties. The crystal structure of Li2ZrCuO4 contains CuO2 chains and two different types of Li positions. The first type is regularly occupied. The second type is 50 % occupied. Thus, there are two equivalent positions for type II between which the Li ions can hop. We have measured Cu2+ ESR and 7Li NMR in Li2ZrCuO4. The ESR data reveal a strong enhancement of quasi-static spin correlations below ∼ 50−60 K and possibly a transition to a magnetically ordered state below ∼ 8 K. The 7Li NMR spectrum consists of two lines which can be assigned to the two nonequivalent Li positions. The analysis of the spectral shape and relaxation times T1 and T2 strongly corroborates the ESR results regarding the slowing down of the Cu spin dynamics and gives a clear indication of the magnetric order at low T. Moreover, the NMR monitors the mobility of the Li ions in Li2ZrCuO4 and yields a characteristic temperature Tg∼ 80 K for the quenching of the hopping of the Li ions between the two type II-positions.