Thermal and dipolar interaction effect on the relaxation in a linear chain of magnetic nanoparticles
Thermal and dipolar interaction effect on the relaxation in a linear chain of magnetic nanoparticles
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DOI：
10.1016/j.jmmm.2020.167538
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发表时间：
2021-03-15
影响因子：
2.7
通讯作者：
Anand, Manish
中科院分区：
文献类型：
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作者：
Anand, Manish
我们通过计算机模拟研究了偶极相互作用磁性纳米颗粒（MNPs）一维链中的弛豫。利用能量势垒的两能级近似，我们进行了动力学蒙特卡罗模拟，以探索作为偶极相互作用强度和温度函数的弛豫机制。假设MNPs的各向异性轴具有随机取向。在高温下，弱偶极相互作用的磁化衰减曲线呈指数型。发现偶极相互作用减缓了磁弛豫，增加了受热波动影响的有效Neel弛豫时间tau(N)。在弱偶极极限下，在很宽的温度范围内，模拟的τ (N)值与解析计算的τ (N)值完全一致。微观分析，如磁矩相关性和动态域形成，也表明铁磁耦合随着偶极相互作用强度的增加或热波动的减少而增加。我们认为，这项工作中提出的概念与数据存储、数字数据处理和磁热疗等应用相关，在这些应用中，MNPs的线性链普遍存在。
We perform computer simulations to study the relaxation in a one-dimensional chain of dipolar interacting magnetic nanoparticles (MNPs). Using the two-level approximation of the energy barrier, we perform kinetic Monte Carlo simulations to probe the relaxation mechanism as a function of dipolar interaction strength and temperature. The anisotropy axes of the MNPs are assumed to have random orientations. At high temperatures, the magnetization decay curve is exponential for weak dipolar interactions. It is found that dipolar interactions slow down the magnetic relaxation and increase the effective Neel relaxation time tau(N), which is affected by thermal fluctuations. In the weak dipolar limit, there is a perfect agreement between simulated and analytically evaluated values of tau(N) for a wide range of temperatures. Microscopic analyses such as magnetic moments correlations and dynamic domain formation also suggest an increase in ferromagnetic coupling with an increase in dipolar interaction strength or decrease in thermal fluctuations. We believe that the concepts presented in this work are relevant in the context of applications such as data storage, digital data processing, and magnetic hyperthermia, in which the linear chain of MNPs are pervasive.