Thermodynamic Properties of the Anisotropic Frustrated Spin-chain Compound Linarite PbCuSO$_4$(OH)$_2$

TL;DR

This study investigates the thermodynamic properties of the frustrated spin-chain compound linarite, revealing the necessity of anisotropic exchange interactions to explain experimental data and suggesting potential stabilization of exotic magnetic phases.

Contribution

It provides a comprehensive thermodynamic analysis of linarite and demonstrates the importance of symmetric anisotropic exchange in modeling its magnetic behavior.

Findings

Identification of five magnetic regions with short-range order effects

Qualitative agreement between experimental data and isotropic models is insufficient

Significant symmetric anisotropic exchange (~10%) is needed to match experimental observations

Abstract

We present a comprehensive macroscopic thermodynamic study of the quasi-one-dimensional (1D) $s = \tfrac{1}{2}$ frustrated spin-chain system linarite. Susceptibility, magnetization, specific heat, magnetocaloric effect, magnetostriction, and thermal-expansion measurements were performed to characterize the magnetic phase diagram. In particular, for magnetic fields along the b axis five different magnetic regions have been detected, some of them exhibiting short-range-order effects. The experimental magnetic entropy and magnetization are compared to a theoretical modelling of these quantities using DMRG and TMRG approaches. Within the framework of a purely 1D isotropic model Hamiltonian, only a qualitative agreement between theory and the experimental data can be achieved. Instead, it is demonstrated that a significant symmetric anisotropic exchange of about 10% is necessary to account for the basic experimental observations, including the 3D saturation field, and which in turn might stabilize a triatic (three-magnon) multipolar phase.