O-17 NMR-STUDY OF LA2-XSRXCUO4 IN THE LIGHTLY-DOPED AND HEAVILY-DOPED REGIONS

A O-17 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 v(Q) 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, PQ in the planar oxygen (O(2)) increases appreciably with Sr doping. By analyzing v(Q) of Cu and O(2), it was shown that the increase of holes on the planar O 2p(sigma) 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 T(c) 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 17K(s,ani) with x also indicates that the hole density at the O 2p(sigma) orbit increases with Sr doping.