scholarly journals Reentrance of the Disordered Phase in the Antiferromagnetic Ising Model on a Square Lattice with Longitudinal and Transverse Magnetic Fields

2021 ◽  
Vol 90 (7) ◽  
pp. 073001
Author(s):  
Ryui Kaneko ◽  
Yoshihide Douda ◽  
Shimpei Goto ◽  
Ippei Danshita
Keyword(s):  
Ising Model ◽  
Magnetic Fields ◽  
Transverse Magnetic ◽  
Square Lattice ◽  
Disordered Phase ◽  
Antiferromagnetic Ising Model

scholarly journals Anisotropic scaling of the two-dimensional Ising model II: surfaces and boundary fields

2020 ◽  
Vol 8 (3) ◽  
Author(s):  
Hendrik Hobrecht ◽  
Fred Hucht
Keyword(s):  
Ising Model ◽  
Boundary Conditions ◽  
Scaling Limit ◽  
Finite Size ◽  
Square Lattice ◽  
Conformal Field ◽  
Anisotropic Scaling ◽  
Finite Lattices ◽  
Antiferromagnetic Ising Model ◽  
Boundary Fields

Based on the results published recently [SciPost Phys. 7, 026 (2019)], the influence of surfaces and boundary fields are calculated for the ferromagnetic anisotropic square lattice Ising model on finite lattices as well as in the finite-size scaling limit. Starting with the open cylinder, we independently apply boundary fields on both sides which can be either homogeneous or staggered, representing different combinations of boundary conditions. We confirm several predictions from scaling theory, conformal field theory and renormalisation group theory: we explicitly show that anisotropic couplings enter the scaling functions through a generalised aspect ratio, and demonstrate that open and staggered boundary conditions are asymptotically equal in the scaling regime. Furthermore, we examine the emergence of the surface tension due to one antiperiodic boundary in the system in the presence of symmetry breaking boundary fields, again for finite systems as well as in the scaling limit. Finally, we extend our results to the antiferromagnetic Ising model.

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.

scholarly journals The magnetic susceptibility on the transverse antiferromagnetic Ising model: Analysis of the reentrant behavior

2016 ◽  
Vol 30 (17) ◽  
pp. 1630011
Author(s):  
Minos A. Neto ◽  
J. Ricardo de Sousa ◽  
Igor T. Padilha ◽  
Octavio D. Rodriguez Salmon ◽  
J. Roberto Viana ◽  
...  
Keyword(s):  
Field Theory ◽  
Phase Diagram ◽  
Magnetic Susceptibility ◽  
Ising Model ◽  
Magnetic Fields ◽  
Effective Field Theory ◽  
Three Dimensional ◽  
Effective Field ◽  
Antiferromagnetic Ising Model ◽  
Reentrant Phenomena

We study the three-dimensional antiferromagnetic Ising model in both uniform longitudinal [Formula: see text] and transverse [Formula: see text] magnetic fields by using the effective-field theory (EFT) with finite cluster [Formula: see text] spin (EFT-1). We analyzed the behavior of the magnetic susceptibility to investigate the reentrant phenomena that we have seen in the same phase diagram previously obtained in other papers. Our results shows the presence of two divergences in the susceptibility that indicates the existence of a reentrant behavior.

ANTIFERROMAGNETIC ISING MODEL DECORATED WITH D-VECTOR SPINS: TRANSVERSAL AND LONGITUDINAL LOCAL FIELDS EFFECTS

1995 ◽  
Vol 09 (26) ◽  
pp. 3387-3400 ◽  
Author(s):  
R. J. VASCONCELOS DOS SANTOS ◽  
S. COUTINHO
Keyword(s):  
Ising Model ◽  
Phase Diagrams ◽  
Local Field ◽  
Local Fields ◽  
Square Lattice ◽  
Antiferromagnetic Ising Model

The effect of a local field acting on decorating classical D-vector bond spins of an antiferromagnetic Ising model on the square lattice is studied for both the annealed isotropic and the axial decorated cases. In both models the effect on the phase diagrams of the transversal and the longitudinal components of the local field acting on the decorating spins are fully analyzed and discussed.

scholarly journals Phase transitions of antiferromagnetic Ising spins on the zigzag surface of an asymmetrical Husimi lattice

2019 ◽  
Vol 6 (3) ◽  
pp. 181500 ◽  
Author(s):  
Ran Huang ◽  
Purushottam D. Gujrati
Keyword(s):  
Phase Transitions ◽  
Ising Model ◽  
Spontaneous Magnetization ◽  
Square Lattice ◽  
Two Dimensional ◽  
Simple Formulation ◽  
First Order ◽  
Husimi Lattice ◽  
Antiferromagnetic Ising Model ◽  
Ising Spins

An asymmetrical two-dimensional Ising model with a zigzag surface, created by diagonally cutting a regular square lattice, has been developed to investigate the thermodynamics and phase transitions on surface by the methodology of recursive lattice, which we have previously applied to study polymers near a surface. The model retains the advantages of simple formulation and exact calculation of the conventional Bethe-like lattices. An antiferromagnetic Ising model is solved on the surface of this lattice to evaluate thermal properties such as free energy, energy density and entropy, from which we have successfully identified a first-order order–disorder transition other than the spontaneous magnetization, and a secondary transition on the supercooled state indicated by the Kauzmann paradox.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

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