89 research outputs found
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
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