Staggered Quadrupolar Phase in the Bond- Diluted Spin-1 Blume-Emery-Griffiths Model

Abstract

The random bond-dilution effects of bilinear interaction parameter J ij between the nearest- neighbor (NN) sites are taken into consideration for the spin-1 Blume-Emery-Griffiths (BEG) model on the Bethe lattice (BL) comprised of two interpenetrating equivalent sublat- tices A and B for given coordination number z in terms of exact recursion relations (ERR). A bimodal distribution for J ij is assumed which is either introduced with probability p or closed with 1 − p. It is assumed that the biquadratic exchange interaction parameter (K) is constant between the NN spins and the single-ion anisotropy parameter (D) is taken to be equivalent on the sublattices A and B. After the study of thermal changes of the order- parameters, the phase diagrams are calculated on possible planes spanned by our system parameters. It is found that the model presents both first- and second-order phase transitions. In addition to the well-known ferromagnetic (F), paramagnetic (P) and ferrimagnetic (FI) phases, the staggered quadrupolar (SQ) phase is also observed. The bicritical point (BCP) for all z and double BCP with z ≥ 4 are observed. The tetracritical point was also found for lower values of p with z ≥ 5.