We report a ${}^{63,65}\mathrm{Cu}$ NMR spin-lattice and transverse relaxation study in the infinite-layer antiferromagnet ${\mathrm{Ca}}_{0.85}{\mathrm{Sr}}_{0.15}{\mathrm{CuO}}_2.$ Experiments were performed in the antiferromagnetic phase between 5.4 and 504 K using two samples of different hole concentration. Despite their low concentration of about ${10}^{-4},$ the holes strongly affect both relaxation types. At $T<\mathrm{}100\mathrm{}$ K, a maximum in the spin-lattice relaxation rate has been quantitatively described considering the effect of holes diffusing with an activation energy of 27 meV which is independent from the concentration. The transverse relaxation is mainly induced by spin-spin indirect coupling. Its strong doping dependence can be directly related to a strong doping dependence of the electronic susceptibility at zero frequency and at the antiferromagnetic wave vector.

• Received 28 January 1998

DOI:https://doi.org/10.1103/PhysRevB.58.2724