Thermodynamic properties of a uniform and nonuniform spin-12 chain as a model for the oxalate-bridged Cu(II) complexes

By using the transfer matrix renormalization group method, we studied the magnetic and thermodynamic properties of the uniform and the nonuniform quantum Heisenberg spin chain with S=12. Compared with experiment results of some compounds, we investigated the effects of different interactions among the magnetic irons of the quantum system, and it is found that the ferro- and antiferromagnetic interaction affect the magnetic characteristics of the system and play important roles in determining the internal energy and the specific heat at finite temperature.