Relaxation behaviours in ferromagnetic monolayers

Abstract

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 ($\tau$) on the aspect ratio $R$ (length over breadth). A power law dependence ($\tau \sim R^{-s}$) 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.