We present a comprehensive macroscopic thermodynamic study of the quasi-one-dimensional (1D) s=21 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.
@article{arxiv.1305.6731,
title = {Thermodynamic Properties of the Anisotropic Frustrated Spin-chain Compound Linarite PbCuSO$_4$(OH)$_2$},
author = {M. Schäpers and A. U. B. Wolter and S. -L. Drechsler and S. Nishimoto and K. -H. Müller and M. Abdel-Hafiez and W. Schottenhamel and B. Büchner and J. Richter and B. Ouladdiaf and M. Uhlarz and R. Beyer and Y. Skourski and J. Wosnitza and K. C. Rule and H. Ryll and B. Klemke and K. Kiefer and M. Reehuis and B. Willenberg and S. Süllow},
journal= {arXiv preprint arXiv:1305.6731},
year = {2013}
}