Interplane magnetic coupling effects in the multilattice compound Y_2Ba_4Cu_7O_{15}

TL;DR

This paper models the interplane magnetic interactions in Y_2Ba_4Cu_7O_{15} using a bilayer Hubbard model, revealing how in-plane antiferromagnetic fluctuations influence interlayer coupling and align with experimental NMR/NQR data.

Contribution

It introduces a bilayer Hubbard model with inequivalent planes to analyze interplane magnetic coupling in Y_2Ba_4Cu_7O_{15}, providing new insights into fluctuation effects.

Findings

Strong in-plane antiferromagnetic fluctuations induce interplane magnetic coupling.

Interlayer fluctuation equalization increases with decreasing temperature and doping.

Model results align qualitatively with NMR and NQR experimental observations.

Abstract

We investigate the interplane magnetic coupling of the multilattice compound Y_2Ba_4Cu_7O_{15} by means of a bilayer Hubbard model with inequivalent planes. We evaluate the spin response, effective interaction and the intra- and interplane spin-spin relaxation times within the fluctuation exchange approximation. We show that strong in-plane antiferromagnetic fluctuations are responsible for a magnetic coupling between the planes, which in turns leads to a tendency of the fluctuation in the two planes to equalize. This equalization effect grows whit increasing in-plane antiferromagnetic fluctuations, i. e., with decreasing temperature and decreasing doping, while it is completely absent when the in-layer correlation length becomes of the order of one lattice spacing. Our results provide a good qualitative description of NMR and NQR experiments in Y_2Ba_4Cu_7O_{15}.