From systematic measurements of Tc, Knight shift, NQR frequency of 63Cu and 17O with high-pressure measurement in high-Tc materials, La2-xSrxCuO4, YBa2Cu3O7 and Tl2Ba2CuO6+y the following results have been obtained. The staggered susceptibility at the zone boundary, χ(Q) which is a measure of the antiferromagnetic spin fluctuation decreases in order of the La, Y and Tl system. χ(Q) is governed by the number of Cu d-holes, n(Cu) and O p-holes, n(O) in the CuO2 plane. χ(Q) increases when n(Cu)/n(O) increases. Tc increases and then decreases with n(Cu)/n(O) having a maximum at an optimum value of n(Cu)/ n(O). Correlation between χ(Q) and Tc has been discussed by assuming χ(Q) to play an essential role for the occurrence of high-Tc superconductivity. The T-dependence of 1/T1 below Tc suggests strongly the d-wave pairing model.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering