Condensed Matter Physics, 2008, vol. 11, No. 3(55), p. 543-553

Title: Magnetic and thermal properties of a one-dimensional spin-1 model
  F.Mancini (Dipartimento di Fisica "E. R. Caianiello" - Unit\`a CNISM di Salerno, Universit\`a degli Studi di Salerno, Via S. Allende, I-84081 Baronissi (SA), Italy) ,
  F.P.Mancini (Dipartimento di Fisica and Sezione I.N.F.N., Universit\`a degli Studi di Perugia, Via A. Pascoli, I-06123 Perugia, Italy)

We study the one-dimensional S=1 Blume-Emery-Griffiths model. Upon transforming the spin model into an equivalent fermionic model, we provide the exact solution within the Green's function and equations of motion formalism. We show that the relevant response functions as well as thermodynamic quantities can be determined, in the whole parameters space, in terms of a finite set of local correlators. Furthermore, considering the case of an antiferromagnetic chain with single-ion anisotropy in the presence of an external magnetic field, we find three plateaus in the magnetization curve. In the neighborhood of the endpoints of the intermediate plateau, the specific heat shows a double peak structure.

Key words: Blume-Emery-Griffiths model, magnetic plateau, exact solution
PACS: 75.10.Pq, 75.10.-b, 75.30.Kz

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