A REAL-SPACE PAIR MODEL FOR THE NMR BEHAVIOR IN HIGH-T(C) CUPRATES

A model for real-space singlet pairs (RSP), hopping on the quasi 2-D a ntiferromagnetic background of localized spins is presented. A crossov er in the temperature dependence of the antiferromagnetic correlation length xi(T) is found. The crossover is caused by the long-wavelength RSP density fluctuations coupled to the antiferromagnetic fluctuations in the 2-D magnetic layers. The NMR characteristics have prononced fe atures around crossover temperature T. The effective ''magnetic mass' ', magnetic energy shift and the size of the ''magnetic cloud'' of the RSP are also calculated. The results are compared with the NMR behavi or observed experimentally in the high-T(c) cuprates.