SPIN GAP AND NUCLEAR MAGNETIC RELAXATIONS IN THE CUPRATE SUPERCONDUCTORS

The differences between the magnetic properties in the normal state of the underdoped and optimally doped high-T-c cuprates are discussed ba sed on a phenomenological model, in which the effect of the spin gap o n the magnetic susceptibility is included. The closely related tempera ture dependences of the uniform static spin susceptibility, the spin-l attice relaxation rate at the planar O sites (17)(T1T)(-1) and Cu site s (63)(T1T)(-1), and the ratio of (63)(T1T)(-1) to the squared Gaussia n relaxation rate at the planar Cu sites T-2G(-2) are considered. The theoretical predictions are in agreement with experiments. (C) 1997 El sevier Science B.V.