THERMODYNAMICS OF ALTERNATING QUANTUM-CLASSICAL (S,1 2)(N) CHAINS WITH Z-Z-TYPE COUPLINGS AND LOCAL ANISOTROPY ON CLASSICAL SPINS/

We propose a general treatment for solving the case of ferrimagnetic c hains made up of two sublattices (S, 1/2), characterized by Z-Z exchan ge couplings between nearest neighbors and a z-uniaxial anisotropy on the classical spins (d=2 point group D-2h or d=3 point group D-infinit y h). The transfer-matrix method is particularly convenient for obtain ing closed-form expressions of the partition function and its derivati ves with respect to the applied field, when this last one is parallel to the z axis of quantization. Consequently, we respectively focus on the conjugated effects of anisotropy and classical-spin dimensionality on the low-temperature behaviors of the parallel magnetization and su sceptibility. The presence of classical spins alternating with quantum ones allows us to focus on the case where the field is normally appli ed to the z axis of quantization. We show that it is only possible to derive a closed-form expression of the normal susceptibility chi(perpe ndicular to) and then study its low-temperature behavior. This work is a good model for testing a previous experimental work achieved on bim etallic chains which are encountered in the compound MnCo(EDTA).6H(2)O .