Experimental Verification of the Gapless Point in the $S$=1 Antiferromagnetic Bond Alternating Chain

TL;DR

This study experimentally confirms the existence of a gapless point at an alternating ratio of approximately 0.6 in an $S$=1 antiferromagnetic bond alternating chain, combining susceptibility, magnetization measurements, and numerical calculations.

Contribution

The paper provides the first experimental verification of the gapless point at $ ext{α} extapprox 0.6$ in the $S$=1 bond alternating chain through combined measurements and numerical analysis.

Findings

Susceptibility shows behavior indicative of a gapless or nearly gapless chain.

Magnetization measurements up to 50 T suggest a very small or zero gap.

Numerical calculations align with experimental data at $ ext{α} extapprox 0.6$.

Abstract

Susceptibility and high field magnetization measurements have been performed on powder samples of an $S$=1 bond alternating chain compound [\{Ni(333-tet)($\mu$-N$_3$)\}$_n$](ClO$_4$)$_n$ (333-tet=tetraamine N,N'-bis(3-aminopropyl)-1,3-propanediamine). As the temperature is decreased, the susceptibility exhibits a round maximum at around 120 K and decreases gradually down to 10 K, and then falls down rapidly with a logarithmic curvature which is behavior of the susceptibility of a gapless or a nearly gapless antiferromagnetic chain. Magnetization up to 50 T at 1.4 K shows no or a very small gap in this compound. We have carried out numerical calculations for the $S$=1 antiferromagnetic bond alternating chain with various alternating ratios $\alpha$ and obtained a very good agreement between experiments and calculations for $\alpha$=0.6. We verify experimentally that the gapless point exists around $\alpha$=0.6.