  We suggest, and demonstrate, a systematic approach to the study of cuprate
superconductors, namely, progressive change of ion size in order to
systematically alter the interaction strength and other key parameters.
R(Ba,Sr)$_2$Cu$_3$O$_y$ (R={La, ... Lu,Y}) is such a system where potentially
obscuring structural changes are minimal. We thereby systematically alter both
dielectric and magnetic properties. Dielectric fluctuation is characterized by
ionic polarizability while magnetic fluctuation is characterized by exchange
interactions measurable by Raman scattering. The range of transition
temperatures is 70 to 107 K and we find that these correlate only with the
dielectric properties, a behavior which persists with external pressure. The
ultimate significance may remain to be proven but it highlights the role of
dielectric screening in the cuprates and adds support to a previously proposed
novel pairing mechanism involving exchange of quantized waves of electronic
polarization.
