The heat capacities of linear Heisenberg chains

Gonzalo Gutiérrez, Eduardo Valdebenito, Sergio M. Davis

P. Schlottmann

B. M. Lisnii

The ground state and the thermodynamics of a spin-1/2 asymmetric diamond Ising--Heisenberg chain are considered. For the $XYZ$ anisotropic Heisenberg interaction, the exact calculations of the free energy, entropy, heat capacity, magnetization, and magnetic susceptibility are performed using the method of decoration-iteration transformation. In the case of antiferromagnetic interactions (Ising and $XXZ$ anisotropic Heisenberg ones), the ground state, magnetization process, temperature dependence of the magnetization, magnetic susceptibility, and heat capacity are investigated. The influence of geometric frustration and quantum fluctuations on these characteristics is studied.

David L. Huber

Hiroki Yamazaki, K. Katsumata

The magnetic properties of $\mathrm{Cs}{\mathrm{Cr}}_{1\ensuremath{-}x}{\mathrm{Mg}}_{x}{\mathrm{Cl}}_{3} (x=0.073)$ are studied by electron-spin-resonance (ESR), magnetic-susceptibility, and heat-capacity measurements to elucidate the edge state in the finite chains of the $S=2$ quasi-one-dimensional Heisenberg antiferromagnet CsCr${\mathrm{Cl}}_{3}$. The results of the ESR measurements in the temperature range 14-40 K are well explained by an effective $S=1$ fractional spin. A crossover between different Curie constants observed in the susceptibility measurements is also explained by assuming $S=1$ free spins at the ends of the finite chains below 40 K. The appearance of the $S=1$ fractional spin can be understood by the valence-bond-solid model.

Б. И. Садовников, Наталья Германовна Иноземцева, V. I. Inozemtsev

The thermodynamics of an inhomogeneous 1D Heisenberg chain with alternating classical and quantum spins is studied. The explicit expressions for the free energy, specific heat, thermal spin correlations and linear susceptibility are found.