We report 63Cu and 205Tl nuclear magnetic resonance (NMR) measurements on trilayered high-Tc compounds TlBa2Ca2Cu3O10-y (Tl-1223) that were synthesized at a high pressure and exhibits a high value of superconducting (SC) transition temperature Tc > 130 K. In the SC state, the nuclear spin-lattice relaxation rate 1/T1 reveals a T3 behavior below Tc, followed by a T1T=const behavior at very low temperatures. The results are accounted for by the d-wave pairing model where the presence of the residual density of the states Nres(EF) is incorporated at the Fermi level to be consistent with the experiments. The important finding is that the size [in Nres (EF)] is much smaller for the present compounds of Tl-1223 with Tc > 130 K than for the previous Tl-2223. Correspondingly, it is shown that an NMR intensity at a satellite peak in the Tl-NMR spectrum, which originates from a possible substitution of Tl for Ca, is much smaller for the former than for the latter. The synthesis technique at a high pressure is found to be a good way to remove such a crystal imperfection due to Tl/Ca intersubstitution. We have demonstrated from a microscopic point of view that as a result of decreasing the degree of disorder effect, the Tc in Tl-1223 has revealed a value higher than 130 K.
|ジャーナル||Physical Review B - Condensed Matter and Materials Physics|
|出版ステータス||Published - 5月 1 2002|
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