Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 32: Correlated Electrons: Poster Session

TT 32.51: Poster

Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B

Quasistatic spin correlations in the frustrated spin-chain cuprate Li₂ZrCuO₄ above T_N — •Yulieth Arango¹, Evgeniya Vavilova², Vladik Kataev^1,2, Olga Volkova³, Aleksandr Vasilyev³, and Bernd Buechner¹ — ¹Institute for Solid State and Material Research IFW Dresden, D-01171 Dresden, Germany — ²Kazan Physical Technical Institute, 420029 Kazan Russia — ³Moscow State University 119992 Moscow Russia

Li₂ZrCuO₄ is a new frustrated quasi-1D spin system with unusual thermodynamic properties due to its proximity to the ferromagnetic critical point. This material contains CuO₂ chains along the crystallographic c-axis, with frustrated exchange interactions between the Cu spins S = 1/2. We carried out high field Cu²⁺ ESR and ⁷Li-NMR measurements on an oriented powder, in a broad temperature range. The ESR data reveal temperature and orientation dependent anisotropy of the g-factor, as well as a progressive broadening of the linewidth below T ≈ 80 K. Two antiferromagnetic resonance modes were observed below T_N ≈ 8 K in long range magnetically ordered state. Surprisingly these modes can be seen also in an extended T-range above T_N. This is in an agreement with the unusual ⁷Li-NMR linewidth and relaxation rates behaviour above T_N . The data analysis suggests the occurrence of quasi-static spin correlations in the chain planes (bc-plane) and anisotropic T-dependent internal field below 80 K. The presence of these features far above T_N indicates a substantial frustration of spin-spin interactions in Li₂ZrCuO₄.