Cylindrical Ising Nanowire in an Oscillating Magnetic Field and Dynamic Compensation Temperature

The magnetic properties of a nonequilibrium spin-1/2 cylindrical Ising nanowire system with core/shell in an oscillating magnetic field are studied by using a mean-field approach based on the Glauber-type stochastic dynamics (DMFT). We employ the Glaubertype stochastic dynamics to construct set of the coupled mean-field dynamic equations. First, we study the temperature dependence of the dynamic order parameters to characterize the nature of the phase transitions and to obtain the dynamic phase transition points. Then, we investigate the temperature dependence of the total magnetization to find the dynamic compensation points as well as to determine the type of behavior. The phase diagrams in which contain the paramagnetic, ferromagnetic, antiferromagnetic, nonmagnetic, surface fundamental phases and tree mixed phases as well as reentrant behavior are presented in the reduced magnetic field amplitude and reduced temperature plane. According to values of Hamiltonian parameters, the compensation temperatures, or the N-, Q-, P-, R-, S-type behaviors in the Neel classification nomenclature exist in the system.Comment: 9 pages, 5 figure

Thermodynamic and magnetic properties of the hexagonal type Ising nanowire

The thermodynamic and magnetic properties of the mixed spin (1/2-1) hexagonal Ising nanowire (HIN) system with core-shell structure have been presented by means of the effective-field theory (EFT) with correlations. The effects of the physical parameters of the system on thermodynmaic and magnetic properties (magnetizations, susceptibilities, internal energies, and free energies and hysteresis curves) are investigated for both ferromagnetic and antiferromagnetic case, in detail. One can find that when the temperature increases the hysteresis loop areas decrease and the hysteresis loops disappear at above critical temperature. Moreover, different hysteresis loop behaviors have been observed such as single, double and triple hysteresis loops in the system. In order to confirm the accuracy of the phase transition points, we also investigate the free energy of the system.Comment: 10 pages, 8 figure

An effective-field theory study of hexagonal Ising nanowire: Thermal and magnetic properties

By means of the effective-field theory (EFT) with correlations, the thermodynamic and magnetic quantities such as magnetization, susceptibility, internal energy, free energy, hysteresis curves and compensation behaviors of the spin-1/2 hexagonal Ising nanowire (HIN) system with core/shell structure have been presented. The hysteresis curves are obtained for different values of the system parameters on both ferromagnetic and antiferromagnetic case. It has been shown that the system only undergoes a second-order phase transition. Moreover, from the thermal variations of the total magnetization, the five compensation types can be found under certain conditions, namely the Q-, R-, S-, P-, and N-types.Comment: 8 pages, 9 figure

Dynamic dipole and quadrupole phase transitions in the kinetic spin-1 model

The dynamic phase transitions have been studied, within a mean-field approach, in the kinetic spin-1 Ising model Hamiltonian with arbitrary bilinear and biquadratic pair interactions in the presence of a time varying (sinusoidal) magnetic field by using the Glauber-type stochastic dynamics. The nature (first- or second-order) of the transition is characterized by investigating the behavior of the thermal variation of the dynamic order parameters. The dynamic phase transitions (DPTs) are obtained and the phase diagrams are constructed in the temperature and magnetic field amplitude plane and found six fundamental types of phase diagrams. Phase diagrams exhibit one or two dynamic tricritical points depending on the biquadratic interaction (K). Besides the disordered (D) and ferromagnetic (F) phases, the FQ + D, F + FQ and F + D coexistence phase regions also exist in the system and the F and F + D phases disappear for high values of K.Comment: 13 pages, 4 figure

The thermal behaviors and phase diagrams of the Ising-type endohedral fullerene with magnetic core and diluted magnetic shell (Core@Shell

We have carried out theoretical studies on Ising-type endohedral fullerene (EF) structure with a dopant magnetic atom encaged within the diluted magnetic spherical cage to examine the evolution in magnetic behaviors. We show how the thermal behaviors and phase diagrams of Ising-type EF are affected by diluted surface, crystal field and exchange couplings. We have used to investigate theoretically the effect of Hamiltonian parameters the effective field calculations within Ising model framework. The model Hamiltonian includes nearest neighbor ferromagnetic and antiferromagnetic center-surface (C-S) interaction as well as ferromagnetic surface interaction. We have shown that the system exhibits the first and second order phase transitions as well as tricritical point. In particular, the conditions for the occurrence of these reentrant and double reentrant behaviors are given explicitly

The effects of the composition, temperature and geometry on the hysteretic properties of the Ising-type barcode nanowire

In the present study, a theoretical approach to investigate the magnetic hysteresis properties in barcode nanowire are used and applied to study Ising system on hexagonal structure. The hysteresis behaviors of Ising-type barcode nanowire (IBN) are studied within the effective-field theory with correlations. The effects of the composition (p), temperature (T) and geometry (interlayer length (d), shell length (s), and wire length (r)) on the hysteresis behaviors are examined in detail. The phase diagrams are presented in the five different planes, namely (p, T), (d, r), (d,T), (r, T) and (s, T) as function of coercive field (HC) and remanence (Mr), and investigated soft/hard the magnetic characteristics of the system. We find that the hysteresis loops areas decrease case as the temperature, wire and lengths increase. Moreover, when p increases the hysteresis loop areas increase. Moreover, HC exhibits an increase in around d = 1 value, then HC does not change with the increasing d values. Theoretical results have qualitatively compatible with some experimental works of multilayer nanowire