arXiv subjects

Ishita Tikader

Publications and source records attributed to Ishita Tikader.

5 recordsLinked to original sources

arXiv2025

Multiple crossover in the decay of metastable volume fraction of a Blume-Capel ferromagnetic needle

The transient behaviours of a Blume-Capel ferromagnetic needle have been studied extensively by Monte-Carlo simulation. The needle has an elongated length in one direction compared to its cross-section. In the context of transient behaviour, we have captured the decay of the metastable state and the magnetic relaxation behaviours in our study. The dependence of metastable behaviour with anisotropy (single site) has been studied. \emph{Interestingly, we have observed multiple (different values of $n$ in different time domains) crossover in the decay of metastable volume fraction (obeying Avrami's law $β\sim {\rm exp}(-Kt^n)$). We have identified the crossover time, and the values of $n$ are estimated precisely.} The mean (magnetic) reversal time has been studied as a function of anisotropy. It is observed to be almost independent of anisotropy for its negative value; however, it is found to decrease exponentially with positive anisotropy. The exponential relaxation behaviour (in the corresponding paramagnetic phase) is observed. The relaxation time was found to depend on the strength of anisotropy.

cond-mat.stat-mech↗

arXiv2025

Strange relaxation and metastable behaviours of the Ising ferromagnetic thick cubic shell

We have studied the equilibrium and nonequilibrium behaviours of the Ising ferromagnetic thick cubic shell by Monte Carlo simulation. Our goal is to find the dependence of the responses on the thickness of the shell. In the equilibrium results, we found that the pseudo-critical temperature of ferro-para phase transition of thick cubic shell increases with the increase of the thickness following a hyperbolic tangent relation. In the nonequilibrium studies, the relaxation time has been found to decrease with the increase of the thickness of the cubic shell. Here three different regimes are found, namely rapid fall, plateau and linear region. The metastable behaviour has been studied also as another kind of non-equilibrium response. The metastable lifetime has been studied as function of the thickness of the cubic shell. A non-monotonic variation of metastable lifetime with the thickness of the shell is observed. A specified thickness for longest-lived metastability has been identified.

cond-mat.stat-mech↗

arXiv2024

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

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-Döring prediction of classical nucleation theory.

cond-mat.stat-mech↗

arXiv2023

Relaxation behaviours in ferromagnetic monolayers

In this article, we briefly review the studies on magnetic relaxation behaviours. The theoretical as well as experimental investigations are reported briefly. A major part of this article is devoted to the recent Monte Carlo investigations into the roles of boundary conditions, dynamics and the Geometrical structures on the relaxation of magnetic monolayers modelled by two-dimensional Ising ferromagnet. We have studied all these effects for a two dimensional Ising system with two types of deformations, namely preserving and area non-preserving.The Glauber protocol and Metropolis dynamical rules are employed in our simulations and we investigated the systems with both periodic and open boundary conditions. The major findings are the exponential relaxation and the dependence of relaxation time ($τ$) on the aspect ratio $R$ (length over breadth). A power law dependence ($τ\sim R^{-s}$) has been observed for larger values of aspect ratio ($R$). The linear thermal ($T$) dependence of exponent ($s$) has been noticed ($s = aT + b$). The transient behaviours of the spin-flip density have also been studied here for both surface and bulk/core. Both the saturated bulk/core and saturated surface spin-flip density are observed to follow the logarithmic dependence $f_{d} = a + b~\log(L)$ with the system size ($L$). For open boundary condition with any kind (Metropolis/Glauber) of dynamical rule, the faster relaxation has been observed. Similarly, Metropolis algorithm yields faster relaxation for any kind (open/periodic) of boundary condition. We appeal to the experimentalists for experimental support which may be applied in judicious {\it magnetic coating} of the credit cards for quicker response.

cond-mat.stat-mech↗

arXiv2023

Effects of geometry, boundary condition and dynamical rules on the magnetic relaxation of Ising ferromagnet

We have studied the magnetic relaxation behavior of a two-dimensional Ising ferromagnet by Monte Carlo simulation. Our primary goal is to investigate the effects of the system's geometry (area preserving) , boundary conditions, and dynamical rules on the relaxation behavior. The Glauber and Metropolis dynamical rules have been employed. The systems with periodic and open boundary conditions are studied. The major findings are the exponential relaxation and the dependence of relaxation time ($τ$) on the aspect ratio $R$ (length over breadth having fixed area). A power law dependence ($τ\sim R^{-s}$) has been observed for larger values of aspect ratio ($R$). The exponent ($s$) has been found to depend linearly ($s=aT+b$) on the system's temperature ($T$). The transient behaviours of the spin-flip density have been investigated for both surface and bulk/core. The size dependencies of saturated spin-flip density significantly differ for the surface and the bulk/core. Both the saturated bulk/core and saturated surface spin-flip density was found to follow the logarithmic dependence $f_d = a + b~log(L)$ with the system size. The faster relaxation was observed for open boundary condition with any kind (Metropolis/Glauber) of dynamical rule. Similarly, Metropolis algorithm yields faster relaxation for any kind (open/periodic) of boundary condition.

cond-mat.stat-mech↗