Interplane electronic spin polarization transfer in the superconducting state of Y2Ba4Cu7O15 as revealed by NQR spin-echo double resonance

We report a spin-echo double resonance study of the plane Cu sites in the s uperconducting state of nearly optimally doped Y2Ba4Cu7O15 employing nuclea r quadrupole resonance. The detailed analysis of the temperature dependence of the indirect in-plane and interplane spin-spin relaxation rate reveals two results: (i) In the normal conducting state, strong antiferromagnetic c orrelations exist between adjacent CuO2 layers. (ii) In the superconducting state, the electronic spin polarization transfer between these layers is d rastically reduced for decreasing temperature. Both findings are consistent with the interlayer tunneling model. [S0031-9007(99)08388-X].