Apparent low-field spin-lattice dispersion in the smectic-A mesophase of thermotropic cyanobiphenyls.
Proton field-cycling spin-lattice relaxometry T1 of the smectic-A mesophase in cyanobiphenyls revealed the presence of steep dispersions in the low-frequency regime. We clearly show that the strong dispersion characteristic of smectic organizations cannot be attributed to the collective molecular dynamics (order director fluctuations), as it is usually interpreted. We present two independent experimental evidences: the dependence of the dispersion with the slew rate of the magnetic field cycle and the dependence of the dispersion with the presence and power of an ultrasonic field.
Anoardo
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Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina. anoardo@mail.famaf.unc.edu.ar
Bonetto
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Kimmich
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R