scholarly journals 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

2006 ◽  
Vol 243 (8) ◽  
pp. 1946-1955 ◽  
Author(s):  
Jozef Strečka ◽  
Lucia Čanová ◽  
Ján Dely
Keyword(s):  
Ising Model ◽  
Critical Behaviour ◽  
Square Lattice ◽  
Integer Spin ◽  
Mixed Spin

scholarly journals 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 ◽  
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.

Phase Diagrams of Diluted Mixed Spin Ising Model on Square Lattice

1998 ◽  
Vol 210 (1) ◽  
pp. 229-235 ◽  
Author(s):  
Z.H. Xin ◽  
G.Z. Wei ◽  
G.Z. Wei ◽  
T.S. Liu ◽  
T.S. Liu
Keyword(s):  
Ising Model ◽  
Phase Diagrams ◽  
Square Lattice ◽  
Mixed Spin

scholarly journals EXACT RESULTS OF THE MIXED-SPIN ISING MODEL ON A DECORATED SQUARE LATTICE WITH TWO DIFFERENT DECORATING SPINS OF INTEGER MAGNITUDES

2008 ◽  
Vol 22 (15) ◽  
pp. 2355-2372 ◽  
Author(s):  
LUCIA ČANOVÁ ◽  
JOZEF STREČKA ◽  
MICHAL JAŠČUR
Keyword(s):  
Ising Model ◽  
Spin System ◽  
Critical Behavior ◽  
Ground State ◽  
Analytical Approach ◽  
Spontaneous Order ◽  
Square Lattice ◽  
Exact Results ◽  
Numerical Result ◽  
Mixed Spin

The mixed-spin Ising model on a decorated square lattice with two different decorating spins of integer magnitudes S B = 1 and S C = 2 placed on horizontal and vertical bonds of the lattice, respectively, is examined within an exact analytical approach based on the generalized decoration–iteration mapping transformation. Besides the ground-state analysis, finite-temperature properties of the system are investigated in detail. The most interesting numerical result to emerge from our study relates to a striking critical behavior of the spontaneously ordered "quasi-1D" spin system. It was found that this quite remarkable spontaneous order arises when one sublattice of the decorating spins (either S B or S C ) tends toward their "nonmagnetic" spin state S = 0, and the system becomes disordered only upon further single-ion anisotropy strengthening. In particular, the effect of single-ion anisotropy upon the temperature dependence of the total and sublattice magnetization is investigated.

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