A new effective-field theory for the Blume-Capel model with a high spin value S is developed by making use of exact spin identities and taking advantage of the differential operator technique. The general formulation for evaluating the transition line and the tricritical point is derived. In...

A new type of effective-field theory that has recently been used with success for many applications concerning the two-state transverse Ising model (spin-12 TIM), is herein extended to the spin-1 TIM. The method, which can explicitly and systematically include correlation effects, is illustrated...

The critical properties of a diluted mixed spin-12 and spin-32 Ising system in a transverse field Ω are investigated within the framework of the effective-field theory. Some interesting phenomena are obtained for the honeycomb lattice, such as the characteristic Ω-dependence of the critical...

A decoupling approximation is introduced for studying the magnetic properties of a spin-S(S≧1/2) Ising system within the framework of the differential operator technique. The formulation yields a statistical accuracy better than that of Bethe–Peierls approximation. It is also applied to the...

The magnetic properties (transition temperature, compensation temperature, total magnetization and initial susceptibility) of a decorated ferrimagnetic Ising system made up of two kinds of magnetic atoms, namely, spin-12 atom and decorated spin-S (S 12) atom with a crystal-field interaction...

Transition temperatures (or phase diagrams) of a multilayer system consisting of spin-12 and spin-32 ferromagnetic Ising layers and disordered interfaces are examined by the use of the new formulation superior to the standard mean-field theory. We find a number of characteristic phenomena. In...