Effects of Ni-to-Cu substitution on the properties of the high-Tcsuperconductor La1.85Sr0.15CuO4-y

We report experimental data about the influence of Ni substitution on the properties of the high-Tc superconductor La1.85Sr0.15Cu1-xNixO4-y, 0≤x≤0.05. Superconductivity is totally suppressed above x=0.04 and the Curie law observed at x=0.05 reveals an effective magnetic moment of 0.7μB instead of 3 μB as for spin (1/2. This result is explained by the existence of a singly &) level. Possibilities for non-s-wave superconductivity are also discussed in conjunction with our experimental data. © 1988 The American Physical Society.