Y NMR imaging of the staggered magnetization in doped Haldane chain Y(2)BaNi(1-x)Mg(x)O(5)

TL;DR

This study uses Y NMR imaging to measure the spin-spin correlation length in doped Haldane chains, confirming theoretical predictions and revealing edge magnetic moments with Curie behavior.

Contribution

It provides a model-independent experimental method to determine the correlation length in doped quantum spin chains using NMR imaging.

Findings

Magnetization decays exponentially with correlation length matching theory.

Edge sites exhibit Curie behavior indicative of effective S=1/2 spins.

The method confirms theoretical predictions for infinite S=1 chains.

Abstract

We present a static, model-independent, experimental determination of the spin-spin correlation length \xi in a quantum spin system. This is achieved in doped Haldane (i.e., S=1 Heisenberg antiferromagnetic) chain Y(2)BaNi(1-x)Mg(x)O(5) by Y NMR imaging of the staggered magnetization induced around the Mg-impurities (i.e., chain boundaries) by magnetic field. The magnitude of this magnetization is found to decay exponentially with \xi equal to the theoretical prediction for an infinite S=1 chain, and the staggered magnetic moment at the edge site showing the Curie behavior of an effective S=1/2 spin.