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Effects of disorder in a single-site anisotropic XY ferromagnet: A Monte Carlo study

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 2025年 626卷

作者： Mallick, Olivia Presidency Univ Dept Phys 86-1 Coll St Kolkata 700073 India

We perform Monte Carlo simulation to study the effects of random disorder on equilibrium phase transition of three-dimensional single-site anisotropic XY ferromagnet. The disorder is incorporated in two ways;having a randomly distributed anisotropy and presence of a quenched random field. The ferro-para transition temperature has been found to increase with the increase of the strength of constant (over the space) anisotropy. In contrast, the system gets ordered at lower temperatures if the anisotropy has random distribution. The effects of quenched random fields are also studied in single-site anisotropic XY ferromagnet. The transition temperature reduces due to the presence of quenched random field. The compensating field (the required amount of field which preserves the critical temperature for isotropic XY ferromagnet) linearly depends on the strength of constant single-site anisotropy. We compute the magnetic and susceptibility exponent ratios for constant single-site anisotropic XY system only via detailed finite-size scaling analysis.

关键词： XY ferromagnet Anisotropy Monte Carlo simulation metropolis algorithm Finite-size analysis Binder cumulant

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External and Crystal Magnetic Field Effects on the Compensation Phenomena of Mixed-Spin (5/2,7/2) Hexagonal Ising Nanowire

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JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 2024年第1期37卷 99-108页

作者： Nmaila, B. Chtaibi, K. Chetaine, A. Laamara, R. Ahl Drissi, L. B. Htoutou, K. Mohammed V Univ Rabat Fac Sci Dept Phys Lab High Energy Phys Modeling & SimulatLPHE MS Rabat Morocco Mohammed V Univ Rabat Fac Sci Dept Phys Lab Nucl PhysCRE FSReactor Phys Environm Nucl Sa Rabat Morocco Mohammed V Univ Rabat Fac Sci Ctr Phys & Math CPM Rabat Morocco CRMEF Reg Ctr Educ & Training Profess Dept Phys Fes Morocco Hassan II Acad Sci & Technol Rabat Morocco

Based on the Ising model, using the Monte Carlo method, we examine the magnetic and thermodynamic characteristics of a ferrimagnetic hexagonal nanowire with spin-5/2 and spin-7/2 of alternate layer structure under external and longitudinal crystal magnetic fields, in particular the physical effect of the external magnetic field on compensation behavior. Moreover, the phase diagrams in the (T, D/J(s)), (T, J(int)/J(s)), and (T, J(sigma)/J(s)) planes have been detailed. Consequently, we have obtained single and double compensation temperatures for the determined longitudinal crystal and external field parameters. The magnetizations of type-N, type-Q, and type-M have been found for certain parameter values in our system. This research was compared with other theoretical and experimental findings.

关键词： Ising model Thermodynamic characteristics Alternate layers Nanowire Compensation behaviors Monte Carlo simulation metropolis algorithm

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A Markov Chain Monte Carlo approach for complex lava flow simulations driven by satellite-derived data

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ENVIRONMENTAL MODELLING & SOFTWARE 2025年 188卷

作者： Zuccarello, Francesco Bilotta, Giuseppe Cannavo, Flavio Cappello, Annalisa Guardo, Roberto Ganci, Gaetana Ist Nazl Geofis & Vulcanol Osserv Etneo Piazza Roma 2 I-95125 Catania Italy

We present a novel optimization strategy for the numerical simulation of lava flows that automatically find the best combination of input parameters to fit observed flows considering their uncertainties. The approach is based on the metropolis algorithm, a Monte Carlo Markov Chain (MCMC) method that performs a sequence of simulations aiming to refine the sampling of unknown parameters to determine their probability distributions. Using this algorithm, we predict the most likely path of lava flows during ongoing eruptions, taking input parameters such as vent locations and Time Average Discharge Rates from satellite imagery. The approach has been validated against synthetic tests on an inclined plane and the 27 February-01 March 2017 eruption at Mt. Etna. This method is the first attempt to use a MCMC method for lava flow modeling, providing several advantages in constraining best-fit values in high-dimensional spaces with complex likelihood functions.

关键词： MCMC metropolis algorithm Fitness function Lava flow simulation

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Monte Carlo study of finite-temperature transition in R2(R = Yb and Er)M2(M = Ti and Sn)O7 anisotropic pyrochlore

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JOURNAL OF THE KOREAN CERAMIC SOCIETY 2024年第4期61卷 537-544页

作者： Khallouq, K. Masrour, R. El Maazouzi, A. Sidi Mohammed Ben Abdellah Univ Fac Sci Dhar El Mahraz Lab Solid Phys Box 1796 Fes Morocco

The Monte Carlo simulations based on the metropolis algorithm was used to investigate the magnetic behavior of Yb2Ti2O7, Er2Ti2O7 and Er2Sn2O7 systems using classical Heisenberg spin model. The thermodynamic observables are averaged over Monte Carlo simulations. The order parameter was computed as a function of temperature for two different configurations. The results show that the thermal phase transition is probably continuous and at most very weakly first order. The variation of the spin components with temperature for the two configurations exhibits different magnetic phases, and the spin configurations are deduced and presented.

关键词： Monte Carlo simulations metropolis algorithm Heisenberg spin model Thermodynamic observables Pyrochlore systems Order parameter

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Nonequilibrium tricritical behavior in anisotropic XY ferromagnet driven by elliptically polarized propagating magnetic field wave

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PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS 2024年 651卷

作者： Mallick, Olivia Acharyya, Muktish Presidency Univ Dept Phys 86-1 Coll St Kolkata 700073 India

The three-dimensional anisotropic XY ferromagnet, driven by an elliptically polarized propagating magnetic field wave, has been extensively investigated by Monte Carlo simulation with the metropolis single spin flip algorithm. Both the effects of the bilinear exchange type and the single-site anisotropies are thoroughly investigated. The time-averaged magnetization (over the complete cycle of the elliptically polarized propagating magnetic field wave) components play the role of the dynamic order parameter. For a fixed set of values of the strength of anisotropy and the field amplitudes, the system has been found to get dynamically ordered at a pseudocritical temperature. The pseudocritical temperature of such a dynamic nonequilibrium phase transition has been found to depend both on the strength of anisotropy and the amplitudes of the elliptically polarized propagating magnetic field wave. A comprehensive phase diagram is represented here in the form of an image plot of the pseudocritical temperature in the plane formed by the strength of anisotropy and field amplitudes. Interestingly, this nonequilibrium phase transition has been found to be discontinuous (first order) for higher values of the field amplitude. On the other hand, the continuous (second order) transition has been noticed for lower values of the field amplitude. Such an interesting nonequilibrium tricritical behavior has been observed in driven XY ferromagnet. The order of such a nonequilibrium phase transition has been confirmed by the thermal variation (near the transition) of the statistical distribution of the order parameter and by the thermal variation of the fourth-order Binder cumulant. In the plane formed by field amplitude and anisotropy, a tricritical line has been shown as the accompanying (and complementary) phase diagram. The dependence of the pseudocritical temperature, on the frequency and wavelength of the elliptically polarized propagating magnetic field wave, has also been reported

关键词： XY model Anisotropy Monte Carlo simulation metropolis algorithm Polarized field wave Tricritical behavior Finite size analysis

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What will be the Euclidean dimension of an Ising ferromagnetic cubic shell?

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JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 2024年 610卷

作者： Tikader, Ishita Acharyya, Muktish Presidency Univ Dept Phys 86-1 Coll St Kolkata 700073 India

The equilibrium and nonequilibrium properties of an Ising ferromagnetic cubic shell have been extensively studied by Monte Carlo simulation using metropolis single spin flip algorithm. Although, geometrically the Euclidean dimension of the cubical shell is three, interestingly, the Ising ferromagnetic cubic shell undergoes ferromagnetic phase transition at a temperature which is very close to that for two-dimensional Ising ferromagnet. Surprisingly, the Ising ferromagnetic cubic shell shows a strange (neither exponential nor stretched exponential) kind of relaxation behaviour, instead of exponential relaxation as usually observed in the two dimensional Ising ferromagnet. The metastable lifetime of a ferromagnetic Ising cubical shell is studied as a function of the applied magnetic field. Here also, the cubic shell behaves more likely a two-dimensional object as found from statistical analysis and comparison with Becker-D & ouml;ring prediction of classical nucleation theory.

关键词： Euclidean dimension Ising ferromagnet Monte Carlo simulation metropolis algorithm Critical point Relaxation Metastable behaviour

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Exploring anisotropic pressure and spatial correlations in strongly confined hard-disk fluids: Exact results

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Physical Review E 2024年第2期110卷 L022601-L022601页

作者： Ana M. Montero Andrés Santos Departamento de Física Instituto de Computación Científica Avanzada (ICCAEx)

This study examines the transverse and longitudinal properties of hard disks confined in narrow channels. Employing an exact mapping of the system onto a one-dimensional polydisperse, nonadditive mixture of hard rods with equal chemical potentials, we compute various thermodynamic properties, including the transverse and longitudinal equations of state, along with their behaviors at both low and high densities. Structural properties are analyzed using the two-body correlation function and the radial distribution function, tailored for the highly anisotropic geometry of this system. The results are corroborated by computer simulations.

关键词： Classical statistical mechanics Confinement Equations of state 2-dimensional systems Polydisperse systems Exact solutions for many-body systems metropolis algorithm

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Monte Carlo study of the phase transitions in the classical XY ferromagnets with random anisotropy

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PHASE TRANSITIONS 2023年第9-10期96卷 668-686页

作者： Mallick, Olivia Acharyya, Muktish Presidency Univ Dept Phys Kolkata India

The three-dimensional anisotropic classical XY ferromagnet has been investigated by extensive Monte Carlo simulation using the metropolis single spin flip algorithm. The magnetisation (M) and the susceptibility (.) are measured and studied as functions of the temperature of the system. For constant anisotropy, the ferro-para phase transition has been found to take place at a higher temperature than that observed in the isotropic case. The system gets ordered at higher temperatures for higher values of the strength of anisotropy. The opposite scenario is observed in the case of random anisotropy. For all three different kinds of statistical distributions (uniform, Gaussian, and bimodal) of random anisotropy, the system gets ordered at lower temperatures for higher values of the width of the distribution of anisotropy. We have provided the phase boundaries in the case of random anisotropy. The critical exponents for the scaling laws M similar to L (beta/nu) and x similar to L (gamma/nu) are estimated through the finite size analysis.

关键词： XY ferromagnet anisotropy Monte Carlo simulation metropolis algorithm finite size analysis binder cumulant

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A Bayes study of inverse Gaussian based strength models with accelerating stress

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COMMUNICATIONS IN STATISTICS-SIMULATION AND COMPUTATION 2023年第8期52卷 3973-3990页

作者： Sen, Rijji Upadhyay, S. K. Univ Calcutta Behala Coll Dept Stat Kolkata India Banaras Hindu Univ Dept Stat Varanasi Uttar Pradesh India Banaras Hindu Univ DST CIMS Varanasi Uttar Pradesh India

The survival probability of a composite material subject to external stress is governed by the condition that the strength of the material must exceed the applied stress. There are several models proposed in the literature for studying such stress-strength relationships, especially with reference to modeling failures in carbon fiber composites. A strong contender in this group is the inverse Gaussian based cumulative damage model. The present paper outlines the Bayes analysis of the four models of this family, two for each of additive and multiplicative stress functions. Further a comparative study, based on a real data set, has been carried out to propose the best model among them.

关键词： Bayes factor Bayes model compatibility Bayes predictive intervals Cumulative damage model Fiber impregnated tows Fibrous carbon composite Inverse Gaussian Distribution metropolis algorithm

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SWAP algorithm for lattice spin models

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Physical Review E 2024年第4期110卷 L043301页

作者： Greivin Alfaro Miranda Leticia F. Cugliandolo Marco Tarzia Laboratoire de Physique Théorique et Hautes Energies CNRS UMR 7589 4 Place Jussieu 75252 Paris Cedex 05 France 1 rue Descartes 75005 Paris France Laboratoire de Physique Théorique de la Matière Condensée CNRS UMR 7600 4 Place Jussieu 75252 Paris Cedex 05 France

We adapted the SWAP molecular dynamics algorithm for use in lattice Ising spin models. We dressed the spins with a randomly distributed length and we alternated long-range spin exchanges with conventional single spin flip Monte Carlo updates, both accepted with a stochastic rule which respects detailed balance. We show that this algorithm, when applied to the bidimensional Edwards-Anderson model, speeds up significantly the relaxation at low temperatures and manages to find ground states with high efficiency and little computational cost. The exploration of spin models should help in understanding why SWAP accelerates the evolution of particle systems and sheds light on relations between dynamics and free-energy landscapes.

关键词： Nonequilibrium statistical mechanics Renormalization group Glassy systems Cavity methods Finite-size scaling Ising model metropolis algorithm Monte Carlo methods Random bond Ising model Simulated annealing Spin lattice models

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