Magnetism of Cu_6 Ge_6 O_{18}-x H_2 O (x = 0 ~ 6), a compound of the one-dimensional Heisenberg $S = 1/2$ model with competing antiferromagnetic interactions

TL;DR

This study investigates the magnetic properties of Cu_6Ge_6O_{18}-xH_2O compounds, revealing their behavior aligns with a one-dimensional Heisenberg S=1/2 model with competing antiferromagnetic interactions, and shows how water content influences magnetic phase transitions.

Contribution

It provides experimental susceptibility data for Cu_6Ge_6O_{18}-xH_2O and analyzes its magnetic behavior within the framework of a one-dimensional Heisenberg model with competing interactions, highlighting the impact of water content.

Findings

Susceptibility matches the 1D Heisenberg S=1/2 model with competing AF interactions.

The system is near a boundary between gapless and gapped magnetic excitations.

The ratio T_N/T_max varies uniquely with water content x, explained by phase transition and disorder effects.

Abstract

We measured the magnetic susceptibilities of Cu$_6$Ge$_6$O$_{18}$-xH$_2$O ($x = 0 \sim 6$). Susceptibility above the antiferromagnetic (AF) transition temperature ($T_{\rm N}$) agrees with susceptibility of the one-dimensional Heisenberg $S = 1/2$ model with competing AF interactions. From the estimated ratio between nearest-neighbor and next-nearest-neighbor AF exchange interactions, the spin system is probably located near a boundary between spin systems with gapless and gapped magnetic excitation. The value of $T_{\rm N}/T_{\rm max}$, where $T_{\rm max}$ is temperature at which the susceptibility is maximum, shows a unique dependence on $x$. The $x$ dependence can be explained qualitatively by taking phase transition as a function of $x$ and the effect of disorder into account.