Random field effects on the phase diagrams of spin-1/2 Ising model on a honeycomb lattice

Abstract

Ising model with quenched random magnetic fields is examined for single Gaussian, bimodal and double Gaussian random field distributions by introducing an effective field approximation that takes into account the correlations between different spins that emerge when expanding the identities. Random field distribution shape dependence of the phase diagrams, magnetization and internal energy is investigated for a honeycomb lattice with a coordination number q = 3. The conditions for the occurrence of reentrant behavior and tricritical points on the system are also discussed in detail.

Effective field theory for the Ising model with a fluctuating exchange integral in an asymmetric bimodal random magnetic field: A differential operator technique

“…where Q 12 = 1 2 tanh(2βJ) from relations (13), (14), (15), (16), so that for the respective critical point we get 2Q c 12 = 1 or tanh(2β c J) = 1 which implies that…”

“…where G k = 3g k0 + 4g k1 + g k2 and the g's functions are defined in (14). The resulting equation for the equilibrium magnetization from ( 9) is…”

“…This procedure presents a great versatility and has been applied to several occasions such as pure, site-and bond-random Ising model, although this procedure shall not yield accurate values for the physical quantities in the critical region due to the absence of long range fluctuations. EFT has already been used in numerous physical problems as a tool to study the magnetic behavior of complex spin systems, such as diluted ferromagnets [9,10,11], pure anisotropic systems [12], disordered systems [13,14], cylindrical nanowires [15].…”

The Effect of Exchange Interaction on Phase Transition Behavior of Magnetic Nanotubes

“…Since Blume-Capel (BC) model was created [1,2] , the magnetothermal properties and phase transition properties of BC models on various lattices have been studied [3][4][5] . Canko's scientific research team explored the phase transition characteristics of single-spin [6] (S=1) system, mixed-spin system [7][8] (S=1/2 and S=1, S=1/2 and S=3/2), and found that the lattice field significantly affected the magnetothermal properties and phase transition of the system, especially the negative crystal field.…”

Phase diagram of the classical Heisenberg model in a trimodal random field distribution

“…A problem associated with the ferromagnetic model in a random field is the survival of the tricritical point [10][11][12][13][14]. Depending on the choice of the random-field distribution, for example when it is given by a symmetric double-delta functions [15], the mean-field approximation gives rise to a tricritical point.…”