Suppression of anti-ferromagnetism by enhanced solubility of Ni in Cu1−xTlxBa2Ca2Cu3−yNiyO10−δ (y = 0, 0.5, 1.0, 1.5) superconductor

Enhanced solubility of Ni in CuO2 planes of Cu1−xTlxBa2Ca2Cu3O10−δ has been observed. The main objective of ferromagnetic Ni substitution in Cu1−xTlxBa2Ca2Cu3O10−δ superconductor at Cu sites was to reduce any possible anti-ferromagnetic order existing in the inner CuO2 planes (IP); this anti-ferromagnetism is suggested to be suppressing the zero resistivity critical temperature [Tc (R = 0)]. If the anti-ferromagnetic order has some role in bringing about superconductivity at a particular temperature, the doping of ferromagnetic Ni would destroy it and hence the superconductivity. Our studies have shown that the doping of 50% ferromagnetic Ni at Cu sites in CuO2 planes does not destroy the superconductivity; most likely reasons for the enhanced superconductivity have also been discussed. The increased doping of Ni beyond 50% destroys superconductivity and the final material becomes perfect insulator. These studies have suggested that Ni possibly breaks the anti-ferromagnetism existing in the inner CuO2 planes, and the critical temperature is not suppressed very much. The post-annealing experiments demonstrated that the magnitude of diamagnetism is enhanced when carriers are optimum in CuO2 planes. These experiments have contradicted the previous notion of non-uniform doping of inner (IP) and outer planes (OP) as a source of suppression of [Tc (R = 0)] of final compound. These experiments have also manifested that the superconductivity and ferromagnetism can co-exist.