T -suppression due to R=Pr,Nd,Eu in (La1?xRx)1.82Sr0.18CuO4

The effect of substitution of rare earth elements (R) on superconductivity and crystal structure is investigated for the samples of (La_1−xR_x)_1.82Sr_0.18CuO₄, R=Pr,Nd,Eu through the measurements of electrical resistivity and lattice parameters. It is revealed thatT _c suppression due to R-elements is not due to their magnetism but can be attributed to two contributions; the reduction of the Madelung site potential at apex sites and the random potential scattering on CuO₂ plane which in effective for pair-breaking in d-wave superconductors, both of which are brought about by the displacement of apex oxygens due to the substitution of R-elements.