Berlin 2012 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 5: Spin Structures and Magnetic Phase Transitions

MA 5.9: Vortrag

Montag, 26. März 2012, 11:45–12:00, H 0112

Z2 vortices in 2D triangular Cr-spin lattices — •Mamoun Hemmida, Hans-Albrecht Krug von Nidda, and Alois Loidl — Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany

Using Electron-Spin-Resonance spectroscopy, we discovered a universal spin-spin relaxation law in two-dimensional frustrated triangular lattice antiferromagnets. The rock salt compounds HCrO2, LiCrO2, and NaCrO2 as well as the delafossite compounds CuCrO2, AgCrO2, and PdCrO2 show a characteristic temperature dependence of the resonance linewidth, indicating relaxation via a certain kind of magnetic vortices, the so-called Z2 vortices. These vortices have been suggested originally by Kawamura and Miyashita (KM) [1]. Their work is an extension to the well-known Berezinskii-Kosterlitz-Thouless (BKT) scenario [2]. Indeed, as it is currently well established [4], the KM scenario seems to be an analogue to the earlier extension of BKT scenario, i.e. Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) model [3], which describes successfully the melting process in a two-dimensional liquid crystal. In the frame of this presentation other recent experimental results obtained by Nuclear-Magnetic-Resonance (NMR) and Muon-Spin-Rotation (μSR) as well as current theoretical studies will be included to promote the interpretation of the up-to-date ESR results. References: [1] H. Kawamura, and S. Miyashita, J. Phys. Soc. Jpn. 53, 4138 (1984). [2] J. M. Kosterlitz and D. J. Thouless, J. Phys. C 6, 1181 (1973). [3] B. I. Halperin and D. R. Nelson, PRL. 41, 121 (1978). [4] M. Hemmida, et al., J. Phys. Soc. Jpn. 80, 053707(2011).