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DF: Dielektrische Festkörper
DF 9: Phasenüberg
änge und Spektroskopie
DF 9.5: Vortrag
Donnerstag, 27. März 2003, 16:30–16:50, HSZ/403
35Cl nuclear magnetic resonance study of critical fluctuations in bis(4-chlorophenyl)sulphone [(ClC6H4)2SO2] — •Dieter Michel1, Abdoulaye Taye1 und Jörn Petersson2 — 1University of Leipzig, Faculty of Physics and Geosciences, 04103 Leipzig, Germany — 2University of the Saarland, Department of Physics,
D-66041 Saarbrücken, Germany
The critical dynamics close to the phase transition from the normal to the incommensurately modulated phase (at ca. 149.7 K) is studied by means of the 35Cl NMR spin-lattice relaxation at the central transitions lines. The temperature dependence of the critical contribution to the spin-lattice relaxation rate 1/T1 above Ti can be described by a critical exponent ζ ≈ 0.67 which is fully consistent with predictions for the universality class of the three-dimensional (3d) XY model. The conclusions drawn from the 35Cl NMR relaxation times are in very good agreement with results derived from 35Cl nuclear quadrupole resonance measurements1 of the same crystal and with results of NMR measurements on other crystals with IC phases2. A broad region for the critical fluctuations is found experimentally. The experimental results very nicely agree with the theoretical treatment3 of T1 using the renormalization group theory.
[1] A. Taye, et al., Phys. Rev. B 66, 174102-1 (2002) [2] F. Decker and J. Petersson, Phys. Rev. B 61, 8993 (2000) [3] F. Decker, et al., Phys. Rev. B 65, 014110-1 (2002)