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The behavior of thermal hysteresis of 2-D hexagonal spin-crossover nanosystem was studied on the basis of microscopic approach, using an Ising-like model. The results were obtained using Monte Carlo method based on the Metropolis algorithm. In the framework of the considered model, a relation between the system size and interaction strength of the neighbor spin-crossover molecules was established. By applying external pressure, a narrowing of the system's hysteresis and a shift of the transition curves toward higher temperature were observed. The application of pressure also leads to a switching between the HS and LS states of the system, which makes such system promising and desirable in sensor applications (as pressure sensors). The influence of the defects on the system transition curves was investigated. Presence of which leads to the narrowing of the hysteresis width. The obtained results of numerical simulations are in accordance with available theoretical and experimental ones of other authors. [ABSTRACT FROM AUTHOR]

A mixed-spin (5/2, 3/2) Ising model is established to describe the antiferroelectric/ferroelectric (AFE/FE) BiFeO 3 /Co bilayer structure. We study the effects of the crystal field, exchange coupling and external longitudinal electric field on the dielectric properties of the bilayer based on Monte Carlo simulation. We illustrate the temperature dependence of polarization, susceptibility, internal energy and specific heat of the system in detail. As well, we depict the phase diagram and point out the rule of the blocking temperature with various parameters. In particular, we find rich and interesting multi-cycle electric hysteresis behaviors. The results show that these parameters play a crucial part in the physical properties of the AFE/FE BiFeO 3 /Co bilayer structure. [ABSTRACT FROM AUTHOR]

We applied Monte Carlo simulation to investigate the thermodynamic properties and hysteresis loops of the hexagonal core-shell nanoparticle described by a ferrimagnetic mixed-spin (3/2, 5/2) Ising model. The results revealed the significance of the single-ion anisotropy, exchange coupling, external magnetic field in dominating various thermodynamic quantities and hysteresis loops. We obtained the variation of the critical temperature with various parameters. Under certain parameter conditions, the system may exhibit rich multiple-loop hysteresis behaviors, depending on the competition among the physical parameters. An Ising model of nanoparticle with hexagonal core-shell structure is proposed. The multiple profiles and saturation values of the magnetization are discovered in the system. [Display omitted] • A ferrimagnetic hexagonal core-shell nanoparticle was proposed under an external magnetic field. • Magnetization, susceptibility, and internal energy were discussed by Monte Carlo simulation. • The compensation temperature was found under the effect of single-ion anisotropy. • Multiple-loop hysteresis behaviors were discovered due to the competition among different physical parameters. [ABSTRACT FROM AUTHOR]