Metallic Nonsuperconducting Phase andD-Wave Superconductivity in Zn-SubstitutedLa1.85Sr0.15CuO4

Measurements of the resistivity, magnetoresistance, and penetration depth were made on films of ${\mathrm{La}}_{1.85}{\mathrm{Sr}}_{0.15}{\mathrm{CuO}}_4$, with up to 12 at. % of Zn substituted for the Cu. The results show that the quadratic temperature dependence of the inverse square of the penetration depth, indicative of $d$-wave superconductivity, is not affected by doping. The suppression of superconductivity leads to a metallic nonsuperconducting phase, as expected for a pairing mechanism related to spin fluctuations. The metal-insulator transition occurs in the vicinity of $k_F\ell \approx 1$, and appears to be disorder driven, with the carrier concentration unaffected by doping.