95 research outputs found
Kinetics of a mixed spin-1/2 and spin-3/2 Ising ferrimagnetic model
We present a study, within a mean-field approach, of the kinetics of a mixed
ferrimagnetic model on a square lattice in which two interpenetrating square
sublattices have spins that can take two values, , alternated
with spins that can take the four values, . We use the
Glauber-type stochastic dynamics to describe the time evolution of the system
with a crystal-field interaction in the presence of a time-dependent
oscillating external magnetic field. The nature (continuous and discontinuous)
of transition is characterized by studying the thermal behaviors of average
order parameters in a period. The dynamic phase transition points are obtained
and the phase diagrams are presented in the reduced magnetic field amplitude
and reduced temperature plane, and in the reduced temperature and
interaction parameter planes, namely in the and planes,
is the reduced crystal-field interaction. The phase diagrams always exhibit a
tricritical point in plane, but do not exhibit in the plane
for low values of . The dynamic multicritical point or dynamic critical end
point exist in the plane for low values of . Moreover, phase
diagrams contain paramagnetic , ferromagnetic , ferrimagnetic
phases, two coexistence or mixed phase regions, and , that
strongly depend on interaction parameters.Comment: 13 pages, 6 figures, submitted to Journal of Magnetism and Magnetic
Material
The Magnetic Reorientation in Ferrimagnetic Systems
The Green function theory is used to study the phenomenon of magnetic reorientation in the ferrimagnetic system. The two-sublattice ferrimagnetic system, with different spins and the intra-sublattice ferromagnetic exchange interactions, is considered. The magnon fluctuations supress in different way the magnetic orders of the sublattices and one obtains two magnetic orders. Each of these orders has different reorientation temperatures
Spatially Anisotropic Spin J₁-J₂ Heisenberg Model for an Antiferromagnetic Square Lattice: Phase Diagrams
The new magnetic materials such as the layered oxide high-temperature superconductor can be well described by the Heisenberg spin model with nearest-neighbor coupling J₁ and next-nearest-neighbor coupling J₂. A generalization of the J₁-J₂ model is the J₁^{x}-J₁^{y}-J₂ model where the nearest-neighbor bonds have different strengths J₁^{x} and J₁^{y} in the x and y directions, respectively. The effect of the couplings J₂ and J₁^{y} on the antiferromagnetic Néel state is investigated within the quantum many-body Green function method
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