Magnetic analog of the isotope effect in cuprates

We present extensive magnetic measurements of the (CaxLa1-x)(Ba1.75-xLa0.25+x)Cu3Oy system with its four different families (x) having a T-c(max)(x) variation of 28% and minimal structural changes. For each family, we measured the Neel temperature, the anisotropies of the magnetic interactions, and the spin-glass temperature. Our results exhibit a universal relation T-c=cJn(s) for all families, where c similar to 1, J is the in-plane Heisenberg exchange, and n(s) is the superconducting carrier density. This relates cuprate superconductivity to magnetism in the same sense that phonon-mediated superconductivity is related to atomic mass.