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In the present work, we will study the effect of dimensionality (i.e 2 + 1 and 3 + 1) has on the different types of coupling in a two-band superconducting system, specifically for the Josephson, bi-quadratic and weak type couplings. This study will be oriented to a ZFC (Zero-Field-Cooling) process and we will see the effect that the variation of temperature for three special cases of the external field (fixed, H < H 1 , H = H 1 and H > H 1) has on the order parameter ψ , phase ψ , magnetization M and free energy G (T) in these superconductors of multibands and a comparison between the behavior of these electronic and thermodynamic variables. This analysis will be carried out using the solution of time-dependent two bands Ginzburg-Landau equations (2B-TDGL). • Dimensionality (2 + 1 and 3 + 1), the type of couplings (Josephson, bi-quadratic and weak), and the temperature of the sample. • Two bands Ginzburg-Landau equations for a two-band system (2B-TDGL). [ABSTRACT FROM AUTHOR]

We used the Curie–Weiss mean-field approximation to study the effects of random single-ion anisotropy and random magnetic field in the phase diagram as well as in the thermodynamic properties of the spin-7/2 Blume–Capel model. The phase diagrams are presented in the planes temperature versus single-ion anisotropy and temperature versus magnetic field, temperature versus random parameters. The dependencies of magnetization are studied as a function of temperature and single-ion anisotropy. • Phase diagrams of the system with a random anisotropies and random field were obtained. • To investigate the system, Curie–Weiss mean-field approximation were used. • First- and second-order phase transition lines for different anisotropies were found. • Tricritical behavior for some values of anisotropy and magnetic field were observed. [ABSTRACT FROM AUTHOR]

Abstract: The phase diagram of an Ising metamagnet in a random magnetic field is studied by using mean-field equations from Bogoliubov''s variational principle. The trimodal probability distribution is applied. The phase diagram in the plane presents continuous and first-order transition lines. The phase transition lines, together with the critical points, were obtained for several random field values. [Copyright &y& Elsevier]

Abstract: By using the differential operator technique and the effective field theory (EFT) scheme, the critical behavior of amorphous classical XY ferromagnet in a random field is studied. The phase diagram in the and planes on a simple cubic lattice for a cluster with two spins is obtained. Calculation is carried out within the EFT approximation. Tricritical points, reentrant phenomena and influence of the random field and amorphization on the transition temperature are discussed. [Copyright &y& Elsevier]

In this paper we have studied the stabilization of the long-range order in ( z ; x ) -plane of two isotropic Heisenberg ferromagnetic monolayers coupled by a short-range exchange interaction ( J ⊥ ), by a long range dipole-dipole interactions and a magnetic field. We have applied a magnetic field along of the z -direction to study the thermodynamic properties above the critical temperature. The dispersion relation ω and the magnetization are given as function of dipolar anisotropy parameter defined as E d = ( g μ ) 2 S / a 3 J ∥ and for other Hamiltonian parameters, and they are calculated by the double-time Zubarev-Tyablikov Green's functions in the random-phase approximation (RPA). The results show that the system is unstable for values of E d ≥ 0.012 with external magnetic field ranging between H / J ∥ = 0 and 1 0 − 3 . The instability appears for E d larger then E d c = 0.0158 with H / J ∥ = 1 0 − 5 , E d c = 0.02885 with H / J ∥ = 1 0 − 4 , and E d c = 0.115 with H / J ∥ = 1 0 − 3 , i.e., a small magnetic field is sufficient to maintain the magnetic order in a greater range of the dipolar interaction. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we used the Cluster Wolff algorithms to simulate the dynamics of the system. We obtained the thermodynamic quantities such as magnetization and susceptibility. Critical temperatures were estimated at the maximum of the susceptibility and with these values we made the phase diagram, versus (the concentration of magnetic bonds) for different values, being the competition parameter. Our results were compared to those obtained by using a new technique in the effective field theory which employs similar probability distribution within the framework of two-site clusters. [Copyright &y& Elsevier]