Magnetic properties in ferroelectric superlattices with two alternative layers described by a transverse spin-1/2 Ising model

The critical. temperature, magnetization, and subceptibility in ferroelectric superlattices with two alternative layers described by a transverse spin-1/2 Ising model are studied using the effective field theory with a probability distribution technique. We discuss an L-t layer superlattice of simple cubic symmetry with nearest-neighbor interactions. We derive the phase diagram, the magnetizations profiles, and the susceptibilities. In such superlattices, the critical temperature can shift to either a lower or higher temperature compared with the corresponding bulk value. The superlattice longitudinal susceptibility diverges at the superlattice critical temperature

The magnetic properties and hysteresis behaviors of the mixed spin-(1/2,1) Ferrimagnetic nanowire

In this work, the mixed spin Ising nanowire model consisting of a spin-1 ferromagnetic core, which is surrounded by a spin-1/2 ferromagnetic surface shell is studied in the presence of magnetic and crystal fields using of the Monte Carlo (MC) Simulations based on the heat bath algorithm. We assume that the exchange interaction between two nearest-neighbor spins at the surface shell and the core is antiferromagnetic. We have examined the effects of the surface and the crystal field on the critical and compensation temperatures. The thermodynamic properties, the hysteresis behaviors are also studied. For appropriate values of the system parameters, the compensation point and multi-loops are found

The Magnetic Properties of Multi-surface Transverse Ferroelectric Ising Thin Films

International audienceThe effective field theory (EFT) based on the transverse Ising model (TIM) is used to study the layer and average polarizations of multi-surface ferroelectric thin film. The effects of the transverse fields and the exchange interactions on the polarization are discussed. It is obvious that the polarizations are affected explicitly by the TIM parameters, and the larger the exchange interactions, the larger the layer and average polarizations. Our theoretical predictions may be a reference for future work in studying the phase transition properties of ferroelectric thin films

Dynamic Magnetic Properties of a Mixed Spin Ising Double-WalledFerromagnetic Nanotubes: A Dynamic Monte Carlo Study

Using the dynamic Monte Carlo simulation, the dynamic critical temperature of a ferromagnetic or ferrimagnetic double-walled nanotubes (DWNTs) is studied within the kinetic Ising model under the presence of a time-dependent oscillating external magnetic and crystal fields with mixed spins S (A) = 1 and S (B) = 3/2. The effects of the time-dependent oscillating external magnetic field, the period of the oscillating magnetic field, and the crystal field on the thermal behavior of the dynamic sub-lattice order parameters and the total dynamic order parameter, total dynamical magnetic susceptibility, dynamical specific heat, and dynamic hysteresis of a DWNTs are studied. Our theoretical predictions may be a reference for future experiment studies of the nanostructures

The ferroelectric properties of films with defect layers

Using the transverse Ising model and the effective field theory based on the probability distribution technique, which accounts for the single-site spin correlations, the phase transition temperature, polarization, susceptibility and hysteresis loops for a ferroelectric (FE) film with defect layers are studied. It is shown that the defect layers in the FE film can induce a strong increase or decrease of the critical temperature of the phase transition due to different exchange interactions in the defect layers, which is connected with the values of the exchange interactions that depend on the distance between the spins. Considering the fact that the interactions can be different in defect layers compared to layers without defects, we have shown that the coercive field decreases in the case of different numbers of defect layers. The results obtained are in qualitative agreement with experimental data on ferroelectric films with different thicknesses

Effect of Seeding Layers on Hysteresis Loops and Phase Transition of the Ferroelectric Thin Film

International audienceThe hysteresis loops and the transition properties of a ferroelectric (FE) thin film with seeding layers are studied using the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions. The effect of the interaction parameters for the seeding layer on the hysteresis loops and phase diagram are also examined. We calculated the critical temperature and the polarization of the FE thin film for different seeding layer structures. We find that the seeding layer can greatly increase the Curie temperature and the polarization of the whole FE thin film. The hysteresis loops are obtained for some typical value of the exchange interaction and the transverse field for a film with one or two seeding layers