On the influence of magnetic and nonmagnetic impurities on Y-based HTSC

In order to study the influence of doping on the physical properties of the superconducting ceramics YBa2Cu3O7-delta, the ceramics samples with different contents of Ni, Zn, Co, Fe and Ga were made. The superconducting fraction, the low-frequency susceptibility in a constant external field and the temperature dependence of magnetic susceptibility in a weak constant field were measured for each sample. The latter parameter permits the critical temperature (the transition onset to be determined) more precisely independently of percolation effects. The experimental results show a stronger suppression of the superconducting state by the nonmagnetic impurities, supporting the existence of d-state pairs in HTSC. The suppression of superconductivity by the magnetic impurities depends on preferential localization of the magnetic ions in the Cu(1) or Cu(2) cells.