Spin-spin Correlation lengths of Bilayer Antiferromagnets

TL;DR

This paper calculates the spin-spin correlation length and structure factor in bilayer antiferromagnets, showing they diverge faster at low temperatures than in single-layer systems, with implications for magnetic fluctuations in superconductors.

Contribution

It provides a theoretical and numerical analysis of correlation lengths in bilayer antiferromagnets, highlighting their rapid divergence compared to single layers.

Findings

Correlation length diverges faster as temperature approaches zero.

Measurements are feasible via neutron scattering despite intensity modulation.

Implications for magnetic fluctuations in doped superconductors.

Abstract

The spin-spin correlation length and the static structure factor for bilayer antiferromagnets, such as YBa$_2$Cu$_3$O$_{6}$, are calculated using field theoretical and numerical methods. It is shown that these quantities can be directly measured in neutron scattering experiments using energy integrated two-axis scan despite the strong intensity modulation perpendicular to the layers. Our calculations show that the correlation length of the bilayer antiferromagnet diverges considerably more rapidly, as the temperature tends to zero, than the correlation length of the corresponding single layer antiferromagnet typified by La$_2$CuO$_4$. This rapid divergence may have important consequences with respect to magnetic fluctuations of the doped superconductors.