Re-appearance of antiferromagnetic ordering with Zn and Ni substitution in La_2-xSr_xCuO₄

The effects of non-magnetic Zn and magnetic Ni substitution for Cu site on magnetism are studied by measurements of uniform magnetic susceptibility for lightly doped La_2-xSr_xCu_1-zM_zO₄ (M = Zn or Ni) polycrystalline samples. For the parent x = 0, Zn doping suppresses the Néel temperature T_N whereas Ni doping hardly changes T_N up to z = 0.3. For the lightly doped samples with T_N ∼ 0, the Ni doping recovers T_N. For the superconducting samples, the Ni doping induces the superconductivity-to-antiferromagnetic transition (or crossover). All the heavily Ni doped samples indicate a spin glass behavior at ∼15 K.