87Rb NMR study of the temperature and electric field dependence of the soliton density near the lock-in transition of incommensurate Rb2ZnCl4 |
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Authors: | J. Petersson E. Schneider |
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Affiliation: | (1) Fachbereich Physik, Universität des Saarlandes, D-6600 Saarbrücken, Federal Republic of Germany |
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Abstract: | The frequency distribution of the87Rb NMR 1/2 –1/2 central transition is measured in a detailed manner as a function of the temperature and the crystal orientation in the normal (N), incommensurate (IC), and commensurate (C) phases of high quality single crystals of Rb2ZnCl4 (RZC). Special emphasis is laid upon the region around the lock-in transition atTc. While in the N and C phases discrete lines are observed, in the IC phase a continuous distribution of frequencies is detected. In a temperature interval not exceeding 15 K aboveTc some centers of intensity termed C lines can be observed in the frequency distribution. They reflect the fact that in the IC phase close toTc several nuclei feel a local surrounding very similar to that of the low temperature C phase. For the first time in the region aroundTc the influence could be studied which an electric field favouring the ferroelectric C phase has on the NMR spectra. The experimental results are related to the temperature and electric field dependence of the soliton density near the lock-in transition. A general definition of the soliton density is developed whose validity is not limited to the very narrow soliton limit. The meaning of this definition is also discussed in terms of well known phenomenological theories of the three phases of RZC. The experimental NMR data can be well described by this general definition.Dedicated to Prof. Dr. H.E. Müser on the occasion of his 60th birthday |
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