The European Physical Journal B ( IF 1.6 ) Pub Date : 2021-01-25 , DOI: 10.1140/epjb/s10051-021-00052-8 Moumita Naskar , Muktish Acharyya
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 \(M_f\) 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.
中文翻译:
布鲁姆-卡佩尔铁磁体的各向异性驱动的磁化反转:蒙特卡洛研究
通过Metropolis算法的蒙特卡洛模拟研究了二维Spin-1 Blume-Capel铁磁体。从初始有序自旋配置开始,在存在相反方向施加的磁场(h)的情况下研究磁化强度的反转。详细研究了反转时间随单中心各向异性强度的变化。观察到指数依赖性。发现平均反转时间随着正负各向异性的系统变化。观察到平均宏观逆转时间线性依赖于适当定义的微观逆转时间。反转后的饱和磁化强度\(M_f \)取决于各向异性强度D。使用形式为\(f(x)的缩放函数,获得了有趣的缩放关系\(| M_f | \ sim | h | ^ {\ beta} f(D | h | ^ {-\ alpha})\ ) = \ frac {1} {1 + e ^ {(xa)/ b}} \)。观察到\(S_i ^ z = 0 \)的密度(被所有\(S_i ^ z = + 1 \)包围)的时间演化呈指数衰减。\(S_i ^ z = -1 \)的平均密度的增长已拟合到函数\(\ rho _ {-1}(t)\ sim \ frac {1} {a + e ^ {(t_c- t)/ c}} \)。特征时间显示为\(t_c \ sim e ^ {-rD} \),并且在\(D = 1.5 \)处观察到指数下降速率的交叉。已经发现亚稳态体积分数服从阿夫拉米定律。