Nuclear magnetic resonance in atomic-scale superconductor/magnet multilayered systems

We investigate the nuclear spin-lattice relaxation rate (T ₁T)^-1 in atomic-scale superconductor/magnet multilayered systems and discuss the discrepancy between two recent (T₁T) ^-1 experiments on Ru in RuSr₂YCu₂O₈. When the magnetic layers are in the antiferromagnetic state, (T ₁T)^-1 in the magnetic layers is shown to decrease with decreasing temperature due to the excitation gap associated with the magnetic ordering. The proximity effect of superconductivity on (T₁T) ^-1 in the magnetic layer is negligibly small. Our result indicates that the temperature dependence of (T₁T)^-1 on Ru in RuSr₂YCu₂O₈ likely originates from the antiferromagnetism in the RuO₂ layers, but not from the superconductivity in the CuO₂ layers.