MAGNETIC SCALING IN CUPRATE SUPERCONDUCTORS

We determine the magnetic phase diagram for the YBa2Cu3O6+x and La2-xSrxCuO4 systems from various NMR experiments. We discuss the possible interpretation of NMR and neutron scattering experiments in these systems in terms of both the nonlinear sigma model of nearly localized spins and a nearly antiferromagnetic Fermi liquid description of magnetically coupled quasiparticles. We show for both the 2:1:4 and 1:2:3 systems that bulk properties, such as the spin susceptibiltiy, and probes at the antiferromagnetic wave vector (pi, pi), such as T-63(1) the Cu-63 spin-lattice relaxation time, both display a crossover at a temperature T-cr, which increases linearly with decreasing hole concentration, from a nonuniversal regime to a z=1 scaling regime characterized by spin pseudogap behavior. We pursue the consequences of the ansatz that T-cr corresponds to a fixed value of the antiferromagnetic correlation length xi and show how this enables one to extract the magnitude and temperature dependence of xi from measurements of T-1 alone. We show that like T-cr, the temperature T* which marks a crossover at low temperatures from the z=1 scaling regime to a quantum disordered regime, exhibits the same dependence on doping for the 2:1:4 and 1:2:3 systems, and so arrive at a unified description of magnetic behavior in the cuprates, in which the determining factor is the planar hole concentration.