ON THE SELECTIVE COPPER SUBSTITUTION WITH Zn 2+ AND Ni 2+ IONS IN LSCO CUPRATES

Direct proof of the role of the CuO2 planes in the occurrence of the high temperature superconductivity in cuprates is got experimentally from the investigation of the behaviour of the critical temperature Tc under gradual substitution of the in plane Cu2+ ions by divalent metal ions M2+. In the present paper, functional dependencies T-c = 7-'c(y) on the y content of M ion are inferred from the existing experimental evidence on La1.85S0.15Cu1-yMyO4 (LSCO) for M2+ denoting either Zn2+ or Ni2+. Data processing and analysis point, in both cases, to a sharp linear decrease of Te under the increase of y, with an M ion dependent slope. The result substantiates the basic hypothesis of the two-dimensional two-band Hubbard model of searching the origins of the high-Tc superconductivity in cuprates inside individual Cuo(2) planes.