35 research outputs found

    Competitive metastable behaviours of surface and bulk in Ising ferromagnet

    No full text
    The reversal of magnetisation has been studied in a three-dimensional Ising ferromagnet by Monte Carlo simulation with Metropolis single spin flip algorithm using random updating scheme. The outer layers are considered as surface. The surface interacts with core with a relative ferromagnetic interaction strength. Depending on the relative interaction strength, the time of reversal of the surface was found to be different from that of the bulk. For weaker relative strength, surface reversal was found to be faster than that of bulk and vice versa for stronger relative interaction strength. A critical value (RcR_c) of relative interaction strength provides same time of reversal of surface and bulk. This critical relative interaction strength was found to be a function of the temperature (T) and applied magnetic field (h). The scaling relation Rchβf(Thα)R_c \sim h^{-\beta }f(Th^{\alpha }), where α=0.23±0.01\alpha =0.23\pm 0.01 and β=0.06±0.01\beta = -0.06\pm 0.01, has been proposed, numerically by the method of data collapse. The metastable volume fractions, for both surface and bulk, were found to follow the Avrami’s law. The critical relative interaction strength (RcR_c) has been observed to decrease in an exponential (ebL1.5)e^{bL^{-1.5}}) fashion with the system size (L)

    Anisotropy-driven reversal of magnetisation in Blume–Capel ferromagnet: a Monte Carlo study

    No full text
    The two-dimensional Spin-1 Blume–Capel ferromagnet is studied by Monte Carlo simulation with Metropolis algorithm. Starting from initial ordered spin configuration, the reversal of magnetisation is investigated in the presence of a magnetic field (h) applied in the opposite direction. The variations of the reversal time with the strength of single-site anisotropy are investigated in details. The exponential dependence was observed. The systematic variations of the mean reversal time with positive and negative anisotropy were found. The mean macroscopic reversal time was observed to be linearly dependent on a suitably defined microscopic reversal time. The saturated magnetisation MfM_f after the reversal was noticed to be dependent of the strength of anisotropy D. An interesting scaling relation was obtained, Mfhβf(Dhα)|M_f| \sim |h|^{\beta }f(D|h|^{-\alpha }) with the scaling function of the form f(x)=11+e(xa)/bf(x)= \frac{1}{1+e^{(x-a)/b}}. The temporal evolution of density of Siz=0S_i^z=0 (surrounded by all Siz=+1S_i^z=+1) is observed to be exponentially decaying. The growth of mean density of Siz=1S_i^z=-1 has been fitted in a function ρ1(t)1a+e(tct)/c\rho _{-1}(t) \sim \frac{1}{a+e^{(t_c-t)/c}}. The characteristic time shows tcerDt_c \sim e^{-rD} and a crossover in the rate of exponential falling is observed at D=1.5D=1.5. The metastable volume fraction has been found to obey the Avrami’s law

    Theoretical studies on switching of magnetisation in thin film

    No full text
    In the present chapter, we focus on the switching of magnetisation, or the metastable lifetime of a ferromagnetic system. In this regard, particularly the Ising model and the Blume-Capel model, have been simulated in the presence of an externally applied magnetic field by the Monte-Carlo simulation technique based on the Metropolis algorithm. Magnetisation switching is found to be faster in the presence of disorder, modelled here by a quenched random field. The strength of the random field is observed to play a similar role to that played by temperature. Becker-D\"oring theory of classical nucleation (originally proposed for the spin-1/2 Ising system) has been verified in the random field Ising model. However, a stronger random field affects the nucleation regime. In a cubic Ising lattice, surface reversal time is found to be different from the bulk reversal time. That distinct behaviour of the surface in contrast to the bulk has been studied here by introducing a relative interfacial interaction strength (RR). Depending on RR, temperature, and applied field, a competitive switching of magnetisation of surface and bulk is noticed. The effect of anisotropy (DD) on the metastable lifetime has been investigated. We report a linear dependency of the mean macroscopic reversal time on a suitably defined microscopic reversal time. The saturated magnetisation MfM_f, after the reversal, is noticed to be strongly dependent on DD. MfM_f, DD, and hh (field) are found to follow a proposed scaling relation. Finally, Becker-D\"oring theory as well as Avrami's law are verified in spin-ss Ising and Blume-Capel models. The switching time depends on the number of accessible spin states.Comment: Invited review article, to appear in Comprehensive Materials Processing (2E), Elsevie

    Code Mixed Cross Script Factoid Question Classification - A Deep Learning Approach

    No full text
    [EN] Before the advent of the Internet era, code-mixing was mainly used in the spoken form. However, with the recent popular informal networking platforms such as Facebook, Twitter, Instagram, etc., in social media, code-mixing is being used more and more in written form. User-generated social media content is becoming an increasingly important resource in applied linguistics. Recent trends in social media usage have led to a proliferation of studies on social media content. Multilingual social media users often write native language content in non-native script (cross-script). Recently Banerjee et al. [9] introduced the code-mixed cross-script question answering research problem and reported that the ever increasing social media content could serve as a potential digital resource for less-computerized languages to build question answering systems. Question classification is a core task in question answering in which questions are assigned a class or a number of classes which denote the expected answer type(s). In this research work, we address the question classification task as part of the code-mixed cross-script question answering research problem. We combine deep learning framework with feature engineering to address the question classification task and enhance the state-of-the-art question classification accuracy by over 4% for code-mixed cross-script questions.The work of the third author was partially supported by the SomEMBED TIN2015-71147-C2-1-P MINECO research project.Banerjee, S.; Kumar Naskar, S.; Rosso, P.; Bandyopadhyay, S. (2018). Code Mixed Cross Script Factoid Question Classification - A Deep Learning Approach. Journal of Intelligent & Fuzzy Systems. 34(5):2959-2969. https://doi.org/10.3233/JIFS-169481S2959296934
    corecore