Bibliogr. s. 961.

Motivated by the rapid development in the synthesis of novel molecule-based magnets, we have investigated magnetic and thermodynamic properties of mixed spin (s–S) exchange coupled chains displaying a simple linear AB or a knotted AB2 arrangement. Approximate approach for s = 1/2 and S ≥ 5/2, treating at an intermediate step spin S operator as a commuting variable and using the transfer matrix technique, is used. Susceptibility, magnetization and heat capacity of both spin systems are evaluated numerically from the corresponding free energy for S = 5/2. Uniform ferromagnetic and antiferromagnetic couplings are discussed. The procedure reproduces the right values of saturation magnetization and the entropy content of the systems, corroborating its correctness. χT curves are shown to depend crucially on the µBH/J ratio. For zero-field heat capacity a double-peak structure is revealed for the AB chain, whereas for the AB2 chain only one broad anomaly is observed.