Abstract
The low-dimensional magnetic systems have been widely investigated theoretically and experimentally in recent years. Strong quantum fluctuations due to low dimensionality may suppress the long-range magnetic ordering, resulting in an opening of a finite spin gap. In this thesis, we presented a detailed NMR study on the three spin gap compounds: Cu2Sc2Ge4O13, Cu2PO4OH, and BiCu2VO6. All the temperature dependence of NMR shifts and spectral line widths exhibit a character of low-dimensional magnetism and the absence of long-range ordering. The hyperfine coupling constants of those compounds can be extracted from the variation of NMR shift against magnetic susceptibility. We investigated the temperature dependence of spin-lattice relaxation rates further. Both NMR shifts and spin-lattice relaxation rates revealed the thermal activated behavior, confirming the existence of spin gap in those compounds. The values of spin gap can be deduced from the dimer model, tetramer model, and empirical formula, respectively.
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