Effect of transition-metal elements on the superconductivity of Y-Ba-Cu-O

We have fabricated samples of the form ${\mathrm{YBa}}_2$(${\mathrm{Cu}}_{0.9}$ ${\mathrm{A}}_{0.1}$ ${)}_3$ ${\mathrm{O}}_{6+\mathrm{y}}$ where A=Ti, Cr, Mn, Fe, Co, Ni, Cu, and Zn. The superconducting state was investigated by both resistance and magnetization measurements. In addition, the magnetic susceptibility above $T_c$ has been measured. $T_c$ was found to be strongly correlated with the size of the paramagnetic moments, largely due to scattering from the magnetic sites. In the sample containing Zn, however, $T_c$ was dramatically reduced due to filling of the antibonding d band.