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

We have fabricated samples of the form YBa₂(Cu0.9{A}0.1)₃{O}6+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.