NMR Evidence for Common Magnetic Behavior in Double Layered Superconducting Cuprates

${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ NMR measurements on (${\mathrm{Pb}}_{0.75}$ ${\mathrm{Cu}}_{0.25}$)${\mathrm{Sr}}_2$ (${\mathrm{Ca}}_{0.5}$ ${\mathrm{Y}}_{0.5}$)${\mathrm{Cu}}_2$ ${\mathrm{O}}_7$ and Y${\mathrm{Ba}}_2$ ${\left({\mathrm{Cu}}_{0.9}{\mathrm{Co}}_{0.1}\right)}_3$ ${\mathrm{O}}_7$ show that the shifts have a similar value and temperature dependence to that of Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{6.48}$. All three have a $T_c$ of 45 K. This behavior parallels that found from a comparative NMR study of Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_4$ ${\mathrm{O}}_8$ and Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{6.8}$ both with $T_c\approx 80$ K. The common behavior of ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$ shifts in these different double layered superconductors strongly suggests that $T_c$ and the spin susceptibility are intimately related in systems where the changes in $T_c$ result from differences in hole concentration.