Magnetic relaxation in terms of microscopic energy barriers in a model of dipolar interacting nanoparticles
Magnetic relaxation in terms of microscopic energy barriers in a model of dipolar interacting nanoparticles
复制标题
偶极相互作用纳米粒子模型中微观能垒的磁弛豫
DOI：
10.1103/physrevb.70.144401
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发表时间：
2003
影响因子：
3.7
通讯作者：
A. Labarta
中科院分区：
文献类型：
--
作者：
Ò. Iglesias;A. Labarta
用蒙特卡罗方法研究了具有偶极相互作用的单畴粒子系统的磁弛豫和磁滞现象。我们通过一个海森堡经典自旋链模型，该自旋链具有随机取向的易轴和对数正态分布的各向异性常数，通过偶极-偶极相互作用相互作用。将所谓的$T\phantom{\rule{0.2em}{0 ex}}\mathrm{ln}（t scin {\ensuremath{\tau}}_{0}）$方法推广到相互作用系统，我们展示了如何将模拟的弛豫曲线与负责长时间弛豫的有效能垒分布联系起来。我们发现，随着相互作用强度的增加，弛豫规律由准对数律变为幂律。这一事实被证明是由于出现了越来越多的小的能量障碍所造成的各向异性能量障碍的减少，因为当地的偶极场的增加。
The magnetic relaxation and hysteresis of a system of single domain particles with dipolar interactions are studied by Monte Carlo simulations. We model the system by a chain of Heisenberg classical spins with randomly oriented easy-axis and log-normal distribution of anisotropy constants interacting through dipole-dipole interactions. Extending the so-called $T\phantom{\rule{0.2em}{0ex}}\mathrm{ln}(t∕{\ensuremath{\tau}}_{0})$ method to interacting systems, we show how to relate the simulated relaxation curves to the effective energy barrier distributions responsible for the long-time relaxation. We find that the relaxation law changes from quasilogarithmic to power-law when increasing the interaction strength. This fact is shown to be due to the appearance of an increasing number of small energy barriers caused by the reduction of the anisotropy energy barriers as the local dipolar fields increase.