205Tl NMR in the High-Tc Superconductor Tl2Ba2CaCu2O8−δ
We report on the NMR Knight shift of 205Tl in Tl2Ba2CaCu2O8−δ for different δ. Due to the variation of the oxygen content Tc ranges from 85K up to 101K. The 205Tl spectra consist of two lines. The main line arises from Tl(1) in the TlO-layer whereas the defect line belongs to Tl(2) in the Ca-layers. The temperature dependence of the line shift of this defect line is strongly related to the oxygen content of the sample. Since the line shift of the defect line is dominated by a negative Knight shift, this Knight shift should be very sensitive to a change of the hole concentration in the CuO2-layers.
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