A 17O NMR study has been carried out for La2-xSrxCuO4 in the lightly- (x=0.075) and heavily-doped (x=0.24) regions in the normal state. Together with the data previously reported for x=0.15, it was found that the nuclear quadrupole frequency νQ in the apical oxygen (O(1)) does not change with x, suggesting that the doped hole does not go into the LaO layer at all. On the contrary, νQ in the planar oxygen (O(2)) increases appreciably with Sr doping. By analyzing νQ of Cu and O(2), it was shown that the increase of holes on the planar O 2pσ orbit is more appreciable than that in the Cu 3d orbit. From the ratio of the hole density in Cu to that in oxygen, and the spin fluctuation probed by 63(T1T), it is suggested that the depression of Tc in the "heavily-doped" region is neither due to the over-doping nor to the collapse of the two-dimensionality, but to other causes. The temperature dependences of the Knight shift 17K in two samples are in sharp contrast with each other. In the lightly-doped region, 17K decreases with decreasing temperature. In the heavily-doped region, however, 17K increases slightly with decreasing temperature, becoming almost T-independent below 100 K. An increase of the anisotropic part of spin Knight shift 17Ks,ani with x also indicates that the hole density at the O 2pσ orbit increases with Sr doping.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering