https://doi.org/10.1007/s100510050492
Mixed spin transverse Ising model with longitudinal random crystal field interactions *
1
Groupe de Mécanique Statistique des
Transitions de Phases et Phénomènes Critiques,
Laboratoire de Physique Théorique,
Université Hassan II,
Faculté des Sciences Aîn Chock,
BP 5366 Maârif, Casablanca, Morocco
2
Institut für Theoretische Physik,
Universität zu Köln,
Zülpicher Strasse 77, 50937 Köln, Germany
Corresponding author: a kluemper@thp.uni-koeln.de
Received:
13
February
1998
Accepted:
17
March
1998
Published online: 15 October 1998
The effect of a longitudinal random crystal field interaction on the phase diagrams of the mixed spin transverse Ising model consisting of spin-1/2 and spin-1 is investigated within the finite cluster approximation based on a single-site cluster theory. In order to expand a cluster identity of spin-1, we transform the spin-1 to spin-1/2 representation containing Pauli operators. We derive the state equations applicable to structures with arbitrary coordination number N. The phase diagrams obtained in the case of a honeycomb lattice (N=3) and a simple-cubic lattice (N=6), are qualitatively different and examined in detail. We find that both systems exhibit a variety of interesting features resulting from the fluctuation of the crystal field interactions.
PACS: 05.30.-d – Quantum statistical mechanics / 05.50.+q – Lattice theory and statistics; Ising problems / 05.70.-a – Thermodynamics
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1998