Tricritical behavior of the Ising antiferromagnet with next-nearest-neighbor ferromagnetic interactions: Mean-field-like tricritical exponents?

1975 ◽  
Vol 11 (7) ◽  
pp. 2689-2692 ◽  
Author(s):  
Michael Wortis ◽  
Fredric Harbus ◽  
H. Eugene Stanley
Keyword(s):  
Nearest Neighbor ◽  
Mean Field ◽  
Ising Antiferromagnet ◽  
Tricritical Behavior ◽  
Ferromagnetic Interactions

Generation of low tehmperature series for Ising models with nearest and next nearest neighbor interactions

1976 ◽  
Vol 54 (16) ◽  
pp. 1646-1650 ◽  
Author(s):  
M. Plischke ◽  
C. F. S. Chan
Keyword(s):  
Low Temperature ◽  
Nearest Neighbor ◽  
Tricritical Point ◽  
Ising Models ◽  
Temperature Data ◽  
Temperature Series ◽  
Bcc Lattice ◽  
Special Cases ◽  
Ising Antiferromagnet ◽  
Ferromagnetic Interactions

We have generalized the code method of Sykes et al. and applied it to the Ising model with nearest and next nearest neighbor interactions. On the bcc lattice, we have obtained the first seven low temperature polynomials for arbitrary sign of the interactions. Special cases of this model are the Ising ferromagnet and the Ising antiferromagnet with next nearest neighbor ferromagnetic interactions. The latter system exhibits a tricritical point which we plan to study using our low temperature data and high temperature series to be obtained in the future.

STAGGERED SYMMETRY AND SINGLE AVERAGE MAGNETIZATION IN DILUTE SYSTEMS

1987 ◽  
Vol 01 (05n06) ◽  
pp. 217-220 ◽  
Author(s):  
SERGE GALAM
Keyword(s):  
Equation Of State ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Average Magnetization ◽  
Ising Antiferromagnet

Mean field treatment of the dilute Ising antiferromagnet in a field is discussed. It is shown that to consider one average single magnetization does indeed account for the staggered symmetry of the model by including implicitly the effects of next nearest neighbor interactions which are not present in the initial Hamiltonian. The dependence of the equation of state on the dilution concentration is also discussed.

Tricritical phenomena in an Ising model with nearest- and next-nearest-neighbor interactions

1977 ◽  
Vol 55 (13) ◽  
pp. 1125-1133 ◽  
Author(s):  
M. Plischke ◽  
D. Zobin
Keyword(s):  
Field Theory ◽  
High Temperature ◽  
Ising Model ◽  
Nearest Neighbor ◽  
Tricritical Point ◽  
Mean Field Theory ◽  
Mean Field ◽  
Temperature Series ◽  
Bcc Lattice ◽  
Ferromagnetic Interactions

We report on the analysis of low and high temperature series for the Ising model with nearest-neighbor antiferromagnetic and next-nearest-neighbor ferromagnetic interactions on the bcc lattice. The high temperature series are complete to β7, the low temperature series to u37. We determine the phase diagram, locate the tricritical point, and estimate the tricritical exponents. The tricritical exponents are only in fair agreement with the predictions of tricritical mean field theory.

Tricritical Behavior of an Ising Antiferromagnet with Next-Nearest Neighbor Ferromagnetic Interaction

1977 ◽  
Vol 42 (3) ◽  
pp. 1055-1056
Author(s):  
Chikao Kawabata ◽  
Jos Rogiers ◽  
George Tuthill ◽  
H. Eugene Stanley
Keyword(s):  
Nearest Neighbor ◽  
Ferromagnetic Interaction ◽  
Ising Antiferromagnet ◽  
Tricritical Behavior

Mean field theory of the orientational properties of (J = 1) hydrogen molecules on the surface of Grafoil

1979 ◽  
Vol 57 (11) ◽  
pp. 1852-1869 ◽  
Author(s):  
A. B. Harris ◽  
A. J. Berlinsky
Keyword(s):  
Field Theory ◽  
Model Comparison ◽  
Nearest Neighbor ◽  
Mean Field Theory ◽  
Computer Calculation ◽  
Mean Field ◽  
Free Energy Calculations ◽  
Axially Symmetric ◽  
Hydrogen Molecules ◽  
Ordered Phases

A mean field theory is developed which is applicable to the orientational behavior of (J = 1) hydrogen molecules on the surface of Grafoil. The hydrogen molecules are assumed to form a triangular lattice in a weak, axially symmetric crystal field, Vc. perpendicular to the substrate and to interact via the electric quadrupole–quadrupole interaction with nearest-neighbor coupling constant Γ. Free energy calculations for the various possible ordered phases are presented, and a Landau expansion is used to investigate the phase boundary between the disordered and ordered phases. A computer calculation, based on the iterative method of James, is used to determine the lines of transition between ordered phases. For almost all values of Vc < 22.5Γ, the disordered to ordered state phase transition is continuous. Four distinct types of ordered phases are found — a four-sublattice phase, two two-sublattice phases, and a one-sublattice phase which resembles an X–Y model. Comparison is made to the recent nmr data of Kubik and Hardy for H2 and D2 on Grafoil.

ABSENCE OF PHASE TRANSITIONS ON TREE STRUCTURES

1993 ◽  
Vol 07 (29n30) ◽  
pp. 1947-1950 ◽  
Author(s):  
RAFFAELLA BURIONI ◽  
DAVIDE CASSI
Keyword(s):  
Long Range ◽  
Nearest Neighbor ◽  
Linear Chain ◽  
Mean Field ◽  
Range Order ◽  
The Other ◽  
Long Range Order ◽  
Field Phase ◽  
Tree Structures ◽  
Bethe Lattices

We rigorously prove that the correlation functions of any statistical model having a compact transitive symmetry group and nearest-neighbor interactions on any tree structure are equal to the corresponding ones on a linear chain. The exponential decay of the latter implies the absence of long-range order on any tree. On the other hand, for trees with exponential growth such as Bethe lattices, one can show the existence of a particular kind of mean field phase transition without long-range order.

SUPERCONDUCTING CLASSES IN THE EXTENDED HUBBARD MODEL

1996 ◽  
Vol 10 (12) ◽  
pp. 1397-1423 ◽  
Author(s):  
MASA-AKI OZAKI ◽  
EIJI MIYAI ◽  
TOMOAKI KONISHI ◽  
KAORU HANAFUSA
Keyword(s):  
Hubbard Model ◽  
Nearest Neighbor ◽  
Mean Field ◽  
Square Lattice ◽  
Extended Hubbard Model ◽  
S Wave ◽  
Ferromagnetic Order ◽  
Numerical Studies ◽  
The Mean

This paper describes group theoretical classification of superconducting states (SC) in the extended Hubbard model with on-site repulsion (U), nearest neighbor attraction (V) and nearest neighbour exchange interaction (J) on the two-dimensional square lattice using the mean field approach. By decomposing the pairing interaction into irreducible parts; A1g, B1g and Eu of D4h point symmetry, we have derived two singlet SCs (s-wave and d-wave) from A1g and B1g, eight triplet SCs from Eu. The first three types of triplet SC have pairing by electrons with antiparallel spin, the second two types have pairing by electrons with equal spin and the last three types are non-unitary and have pairing by only up-spin electrons. We showed that three non-unitary states have to be accompanied with a ferromagnetic order from the structure of the maximal little groups. We performed numerical studies for these SCs. For parameters and electron density favorable for the ferromagnetic order, a non-unitary SC coexistent with ferromagnetism is most stable.

Re-Examination of A1 → L10 Ordering: Generalized Bragg-Williams Model with Elastic Relaxation

2011 ◽  
Vol 172-174 ◽  
pp. 608-617 ◽  
Author(s):  
William A. Soffa ◽  
David E. Laughlin ◽  
Nitin Singh
Keyword(s):  
Nearest Neighbor ◽  
Binary Solution ◽  
Mean Field ◽  
Lattice Relaxation ◽  
Two Phase ◽  
First Order ◽  
Tetragonal Lattice ◽  
Wide Range ◽  
Third Law Of Thermodynamics ◽  
The Mean

The tetragonal lattice relaxation has been included in the thermodynamics of the fcc→L10ordering to produce a first-order character of the transition within the mean field description of the binary solution energetics. In view of growing interest in such systems e.g. Fe-Pd and Co-Pt alloys, which display a wide range of applications relevant to current and futuristic technologies, the fcc→L10two-phase field is re-examined utilizing a generalized Bragg-Williams approach including first and second nearest neighbor interactions. The thermodynamic behavior is examined in the limit of T→0K and discussed in terms of the implications of the Third Law of Thermodynamics.

scholarly journals Investigation of the Critical Behavior, Magnetocaloric Effect and Hyperfine Structure in the Fe72Nb8B20 Powders

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4476
Author(s):  
Safia Alleg ◽  
Thaounza Chabi ◽  
Nadia Bensebaa ◽  
Joan Saurina ◽  
Lluisa Escoda ◽  
...  
Keyword(s):  
Amorphous Phase ◽  
Magnetic Measurements ◽  
Mean Field ◽  
Entropy Change ◽  
Mössbauer Spectrometry ◽  
Mechanically Alloyed ◽  
Scanning Calorimetry ◽  
Mean Field Model ◽  
Mossbauer Spectrometry ◽  
Ferromagnetic Interactions

Microstructure as well as magnetic, thermal and magnetocaloric properties of the mechanically alloyed Fe72Nb8B20 powders have been investigated by means of Mössbauer spectrometry, differential scanning calorimetry (DSC), and magnetic measurements. The Mössbauer spectrometry results showed the formation of nanostructured Fe(B) and Fe(Nb) solid solutions, Fe2B boride, and an amorphous phase. The endothermic and exothermic peaks that are observed in the DSC curves might be related to the Curie temperature, and the crystallization of the amorphous phase, respectively. The critical exponent values around the magnetic phase transition of the amorphous phase (TC = 480 K), are deduced from the modified Arrott plots, Kouvel−Fisher curves and critical isotherm examination. The calculated values (β = 0.457 ± 0.012, γ = 0.863 ± 0.136 and δ = 3.090 ± 0.004) are near to those of the mean field model, revealing a dominating role of magnetic order arising due to long-range ferromagnetic interactions, as the critical exponents are mean-field-like. The maximum entropy change and the refrigerant capacity values are 1.45 J/kg·K and 239 J/kg, respectively, under a magnetic field of 5 T.

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