Condensed Matter Physics, 2006, vol. 9, No. 1(45), p. 179186, English
DOI:10.5488/CMP.9.1.179
Title:
Nonuniversal critical behaviour of a mixedspin Ising model on the extended Kagomé lattice
Author(s):
 J.Strecka
(Department of Theoretical Physics and
Astrophysics, Faculty of Science, P. J. Safárik
University, Park Angelinum 9, 040 01 Kosice, Slovak
Republic)
,

 L.Canova
(Department of Theoretical Physics and
Astrophysics, Faculty of Science, P. J. Safárik
University, Park Angelinum 9, 040 01 Kosice, Slovak
Republic)

The mixed spin1/2 and spin3/2 Ising model on the extended
Kagom\'e lattice is solved by establishing a mapping
correspondence with the eightvertex model. When the parameter of
uniaxial singleion anisotropy tends to infinity, the model system
becomes exactly solvable as the staggered eightvertex model
satisfying the freefermion condition. The critical points within
this manifold can be characterized by critical exponents from the
standard Ising universality class. The critical points within
another subspace of interaction parameters, which corresponds to a
coexistence surface between two ordered phases, can be
approximated by corresponding results of the uniform eightvertex
model satisfying the zerofield condition. This coexistence
surface is bounded by a line of bicritical points that have
nonuniversal continuously varying critical indices.
Key words: Ising model, eightvertex model, bicritical points,
nonuniversality
PACS: 75.10.Hk, 05.50.+q, 75.40.Cx
