MAGNETIC FIELD INFLUENCE ON THERMODYNAMIC CHARACTERISTICS OF SPIN-1 ISING MODEL WITH BILINEAR AND QUADRUPOLAR INTERACTIONS. CLUSTER APPROXIMATION

摘要

The influence of external magnetic field on spin-1 Ising model with bilinear and quadrupolar interactions is studied within the cluster approximation. Phase diagrams in the (magnetic field, temperature) plane are constructed at different values of quadrupolar interaction. Temperature dependences of magnetization and quadrupolar moment are obtained at different values of the model parameters. We show that at those values of the quadrupolar interaction when at zero magnetic field the system undergoes the temperature phase transition between quadrupolar and paramagnetic phases, the external magnetic field not only induces a non-zero magnetization in ``paramagnetic'' and ``quadrupolar'' phases, but also can split this transition into a cascade of phase transitions: ``quadrupolar'' a ferromagnetic a ``paramagnetic'' phase.