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| Paper IPM / Physic / 8857 |
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| Abstract: | |||||||
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We have studied the thermodynamic behavior of the bond alternating
Antiferromagnetic-Ferromagnetic and
Antiferromagnetic-Antiferromagnetic Heisenberg mixed spin chains.
The cumulant expansion has been used as an analytic approach to
obtain the quasi-classical Hamiltonian of a (S, s)
ferrimagnetic bond alternating spin chain within the second order
corrections. The internal energy and the specific heat per unit cell
are calculated via the classical Hamiltonian. Quantum Monte carlo
method has also been implemented as a reference approach to obtain
the thermodynamic properties of the model. Results of the cumulant
expansion are in good agreement with the Quantum Monte Carlo ones.
The analytical results obtained by cumulant expansion can also be
applied to the homogeneous (S=s=1) alternating bond spin chain
Ni2(EDTA)·6H2O, in the absence of single ion
anisotropy parameter.
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