We have studied the effects of magnetic and non-magnetic alloying elements on the superconductivity of the high-Tc compound YBa2Cu3Oy by replacing Cu with Fe and Al. Both alloying elements Fe and Al change the crystal symmetry from orthorhombic to tetragonal and the normal conductivity for metal-like to insulator-like with increasing alloy concentration. The suppression rate of Tc due to Fe is found to be comparable to that due to Al, i.e. ≈6 K/at%. The temperature gradient of the upper critical field, i.e. -(dHc2/dT) of alloyed samples YBa2(Cu0.98Fe0.02)3Oy and YBa2(Cu0.99Al0.01)3Oy are about one half of ≈3 T/K of YBa2Cu3Oy.
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