Thermodynamic properties of tetrameric bond-alternating spin chains

TL;DR

This paper investigates the thermodynamic behavior of a tetrameric bond-alternating Heisenberg spin chain with mixed exchange interactions, revealing ferrimagnetic features and matching experimental data for a specific copper compound.

Contribution

It provides a detailed numerical analysis of the thermodynamic properties of a specific spin chain model, connecting theoretical predictions with experimental results.

Findings

Uniform susceptibility shows ferrimagnetic features.

Both susceptibilities diverge as T approaches 0.

Double-peak structure in specific heat temperature dependence.

Abstract

Thermodynamic properties of a tetrameric bond-alternating Heisenberg spin chain with ferromagnetic-ferromagnetic-antiferromagnetic-antiferromagnetic exchange interactions are studied using the transfer-matrix renormalization group and compared to experimental measurements. The temperature dependence of the uniform susceptibility exhibits typical ferrimagnetic features. Both the uniform and staggered magnetic susceptibilities diverge in the limit $T\to 0$, indicating that the ground state has both ferromagnetic and antiferromagnetic long-range orders. A double-peak structure appears in the temperature dependence of the specific heat. Our numerical calculation gives a good account for the temperature and field dependence of the susceptibility, the magnetization, and the specific heat for Cu(3-Clpy)$_{2}$(N$_{3}$)$_{2}$ (3-Clpy=3-Chloroyridine).