Phase Diagrams of Diluted Mixed Spin Ising Model on Square Lattice

AbstractWithin effective field theory (EFT), the critical properties of a random transverse crystal field Ising model with bond dilution are studied on a square lattice. Under both weak and strong bond dilution conditions, we consider three cases (α = 0,±0.5) of a transverse crystal field ratio, obtaining global phase diagrams in T−D x space for changes in the random transverse crystal field concentration. The phase diagrams obtained for a weak bond dilution are very similar in shape to those of pure bond but with decreases in corresponding ordered phases and critical values. However, the phase diagrams for a strong bond dilution exhibit varieties, including a change in reentrant phenomenon, the occurrence of transverse crystal field degeneration, and the opposite direction crossover of temperature peak value.

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Weak universal critical behaviour of the mixed spin-(1/2,S ) Ising model on the Union Jack (centered square) lattice: integer versus half-odd-integer spin-S case

physica status solidi (b) ◽

10.1002/pssb.200642018 ◽

2006 ◽

Vol 243 (8) ◽

pp. 1946-1955 ◽

Cited By ~ 6

Author(s):

Jozef Strečka ◽

Lucia Čanová ◽

Ján Dely

Keyword(s):

Ising Model ◽

Critical Behaviour ◽

Square Lattice ◽

Integer Spin ◽

Mixed Spin

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PHASE TRANSITIONS OF THE MIXED-SPIN ISING MODEL ON A DECORATED LATTICE WITH THE NEAREST-NEIGHBOR INTERACTION BETWEEN DECORATING SPINS

International Journal of Modern Physics B ◽

10.1142/s0217979209053680 ◽

2009 ◽

Vol 23 (24) ◽

pp. 4963-4976 ◽

Cited By ~ 4

Author(s):

A. BENYOUSSEF ◽

A. EL KENZ ◽

M. EL YADARI ◽

M. LOULIDI

Keyword(s):

Phase Transitions ◽

Ising Model ◽

Phase Diagrams ◽

Nearest Neighbor ◽

Mean Field ◽

Nearest Neighbors ◽

Field Approximation ◽

Mean Field Approximation ◽

Neighbor Interaction ◽

Mixed Spin

A mean-field approximation is developed for a decorated ferrimagnetic Ising model, in which the two magnetic atoms A and B have spins σ=1/2 and S=1, respectively. In this system, the exchange interaction between nearest-neighbors of atom B is taken into account. Some interesting phenomena, such as the appearance of three types of phase diagrams and the existence of one and two compensation points are found. Phase diagrams and temperature dependence of the magnetizations of the system are investigated in detail.

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Weak Singularities of the Isothermal Entropy Change as the Smoking Gun Evidence of Phase Transitions of Mixed-Spin Ising Model on a Decorated Square Lattice in Transverse Field

Entropy ◽

10.3390/e23111533 ◽

2021 ◽

Vol 23 (11) ◽

pp. 1533

Author(s):

Jozef Strečka ◽

Katarína Karl’ová

Keyword(s):

Magnetic Field ◽

Phase Transitions ◽

Ising Model ◽

Magnetocaloric Effect ◽

Entropy Change ◽

Transverse Magnetic ◽

Continuous Phase ◽

Square Lattice ◽

Mixed Spin ◽

Weak Singularities

The magnetocaloric response of the mixed spin-1/2 and spin-S (S>1/2) Ising model on a decorated square lattice is thoroughly examined in presence of the transverse magnetic field within the generalized decoration-iteration transformation, which provides an exact mapping relation with an effective spin-1/2 Ising model on a square lattice in a zero magnetic field. Temperature dependencies of the entropy and isothermal entropy change exhibit an outstanding singular behavior in a close neighborhood of temperature-driven continuous phase transitions, which can be additionally tuned by the applied transverse magnetic field. While temperature variations of the entropy display in proximity of the critical temperature Tc a striking energy-type singularity (T−Tc)log|T−Tc|, two analogous weak singularities can be encountered in the temperature dependence of the isothermal entropy change. The basic magnetocaloric measurement of the isothermal entropy change may accordingly afford the smoking gun evidence of continuous phase transitions. It is shown that the investigated model predominantly displays the conventional magnetocaloric effect with exception of a small range of moderate temperatures, which contrarily promotes the inverse magnetocaloric effect. It turns out that the temperature range inherent to the inverse magnetocaloric effect is gradually suppressed upon increasing of the spin magnitude S.

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