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

Abstract

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 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 was found. The mean macroscopic reversal time was observed to be linearly dependent on a suitably defined microscopic reversal time. The saturated magnetisation $M_f$ after the reversal was noticed to be dependent of the strength of anisotropy $D$. An interesting scaling relation was obtained, $|M_f| \sim |h|^{\beta}f(D|h|^{-\alpha})$ with the scaling function of the form $f(x)= \frac{1}{1+e^{(x-a)/b}}$. The temporal evolution of density of $S_i^z=0$ (surrounded by all $S_i^z=+1$) is observed to be exponentially decaying. The growth of mean density of $S_i^z=-1$ has been fitted in a function $\rho_{-1}(t) \sim \frac{1}{a+e^{(t_c-t)/c}}$. The characteristic time shows $t_c \sim e^{-rD}$ and a crossover in the rate of exponential falling is observed at $D=1.5$. The metastable volume fraction has been found to obey the Avrami's law.