The Ising model in the presence of a random field is investigated within the mean field approximation based on Landau expansion. The random field is drawn from the asymmetric and anisotropic bimodal probability distribution P(hi)=pδ(hi−h0)+qδ(hi+λ∗h0), where the site probabilities p,q...

Properties of semi-infinite (S=1) Heisenberg ferromagnet with biquadratic exchange were studied in terms of surface exchange (ε=IS/I) and biquadratic coupling (a). It was shown that a strict correlation exists, depending on ε, between the type of surface spin waves (acoustic or optical) and...

We study a geometrically frustrated triangular Ising antiferromagnet in an external magnetic field which is selectively diluted with nonmagnetic impurities employing an effective-field theory with correlations and Monte Carlo simulations. We focus on the frustration-relieving effects of such a...

The phase diagram of the ABpC1−p mixed ferro-ferrimagnetic ternary alloy consisting of Ising spins sA=1, sB=32, and sC=12 is investigated by the use of a mean-field theory based on the Bogoliubov inequality for the Gibbs free energy. The effect of the single-ion anisotropy on the transition...

Using the two-spin cluster mean-field method, the spin-1 Heisenberg model with Dzyaloshinskii–Moriya (DM) interactions is studied for the simple cubic lattice. For the case of the DM vector coupling D⇒=Dz^ (D is the DM interaction parameter and z^ is the unit vector of the z-axis direction),...

The Ising model in the presence of a random field, drawn from the asymmetric and anisotropic trimodal probability distribution P(hi)=pδ(hi−h0)+qδ(hi+λ∗h0)+rδ(hi), is investigated. The partial probabilities p,q,r take on values within the interval [0,1] consistent with the constraint...

The Ising model in the presence of a random field is investigated within the mean field approximation based on Landau expansion. The random field is drawn from the trimodal probability distribution P(hi)=pδ(hi−h0)+qδ(hi+h0)+rδ(hi), where the probabilities p,q,r take on values within the...

The phase diagrams of the bilayer spin-32 Ising model on the Bethe lattice is analyzed by taking into account the intralayer coupling constants of the two layers (J1,J2), interlayer coupling constant between the layers (J3) and crystal field interaction (D) for the coordination number q=3 by...

We have studied the Blume–Capel model by using the expanded Bethe–Peierls approximation. In this approximation, the system is taken as a group of chains composed of a central chain and its nearest-neighbor chains. The nearest-neighbor chains are in an effective field produced by the other...

The Ising model, in the presence of a random field, is investigated within the mean-field approximation based on Landau expansion. The random field is drawn from the bimodal probability distribution P(h)=pδ(h−h0)+(1−p)δ(h+h0), where the probability p assumes any value within the interval...