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Paper   IPM / P / 8857
School of Physics
  Title:   Thermodynamic Properties of AF-F and AF-AF Bond Alternating Spin Chains
  Author(s): 
1.  J. Abouie
2.  A. Langari
3.  S.A. Ghasemi
  Status:   Preprint
  Journal:
  Year:  2008
  Supported by:  IPM
  Abstract:
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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