INFLUENCE OF MAGNETIC IMPERFECTIONS ON THE LOW-TEMPERATURE PROPERTIESOF D-WAVE SUPERCONDUCTORS

We consider the influence ot planar ''magnetic'' imperfections which d estroy the local magnetic order, such as Zn impurities or Cu2+ vacanci es, on the low-temperature properties of the cuprate superconductors. In the unitary limit, at low temperatures, for a d(x)2-y2 pairing stat e such imperfections produce low-energy quasiparticles with an anistro pic spectrum in the vicinity of the nodes. We find that for the La2-xS rxCuO4 system, one is in the quasi-one-dimensional regime of quasipart icle scattering, discussed recently by Altshuler, Balatsky, and Roseng ren, for impurity concentrations in excess of approximately 0.16% wher eas Ya-Ba-Cu-O7 appears likely to be in the true two-dimensional scatt ering regime for Zn concentrations less than 1.6%. We show the neutron -scattering results of Mason et al. [Phys. Rev. Lett. 71, 919 (1993)] on La1.86Sr0.14CuO4 provide strong evidence for ''dirty d-wave'' super conductivity in their samples. We obtain simple expressions for the dy namic spin susceptibility and Cu-63 spin-lattice relaxation time, 63T1 , in the superconducting state.