A generalized spherical version of the Blume-Emery-Griffits model with ferromagnetic and antiferromagnetic interactions
Abstract
We have investigated analitycally the phase diagram of a generalized spherical version of the Blume-Emery-Griffiths model that includes ferromagnetic or antiferromagnetic spin interactions as well as quadrupole interactions in zero and nonzero magnetic field. We show that in three dimensions and zero magnetic field a regular paramagnetic-ferromagnetic (PM-FM) or a paramagnetic-antiferromagnetic (PM-AFM) phase transition occurs whenever the magnetic spin interactions dominate over the quadrupole interactions. However, when spin and quadrupole interactions are important, there appears a reentrant FM-PM or AFM-PM phase transition at low temperatures, in addition to the regular PM-FM or PM-AFM phase transitions. On the other hand, in a nonzero homogeneous external magnetic field , we find no evidence of a transition to the state with spontaneous magnetization for FM interactions in three dimensions. Nonethelesss, for AFM interactions we do get a scenario similar to that described above for zero external magnetic field, except that the critical temperatures are now functions of . We also find two critical field values, , at which the reentrance phenomenon dissapears and (), above which the PM-AFM transition temperature vanishes.
Keywords
Cite
@article{arxiv.cond-mat/0006324,
title = {A generalized spherical version of the Blume-Emery-Griffits model with ferromagnetic and antiferromagnetic interactions},
author = {S. E. Savel'ev and Guillermo Ramirez-Santiago},
journal= {arXiv preprint arXiv:cond-mat/0006324},
year = {2009}
}
Comments
21 pages, 6 figs. Title changed, abstract and introduction as well as section IV were rewritten relaxing the emphasis on spin S=1 and Figs. 5 an 6 were improved in presentation. However, all the results remain valid. Accepted for publication in Phys. Rev. B