Fast switching of magnetic nanoparticles: Simulation of thermal noise effects using the Langevin dynamics
Fast switching of magnetic nanoparticles: Simulation of thermal noise effects using the Langevin dynamics
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DOI：
10.1109/tmag.2002.801905
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发表时间：
2002-09-01
影响因子：
2.1
通讯作者：
Berkov, DV
中科院分区：
文献类型：
--
作者：
Berkov, DV
最直接的方法来模拟快速切换磁系统的随机运动方程的磁矩（朗之万动力学）的解决方案，其中考虑到热波动的热（随机）场H-FL。在本文中，我们首先解决一个重要的方法问题，这种形式主义：选择的随机微积分（伊藤或Stratonovich）。我们证明，伊藤和Stratonovich随机积分给出相同的结果，尽管乘法噪声存在于随机Landau-Lifshitz-吉尔伯特方程。讨论Hfl的相关性（通常假设其在空间和时间上都是6相关的），我们指出该场的有限相关时间和半径不仅可能是由于物理原因（热浴相关），也可能是由于连续问题的有限元表示。之后，我们提出了模拟结果的影响，热波动的快速开关的磁性纳米元件。我们考虑了三种典型的情况：1）热噪声对开关的影响，这也会发生在没有热波动的情况下（热辅助开关）; 2）热诱导的亚稳态开关;以及3）由于热波动而改变开关模式。
The most straightforward method to simulate fast switching in magnetic systems is the solution of stochastic equations of motion for magnetic moments (Langevin dynamics), where thermal fluctuations are taken into account by the thermal (random) field H-fl. In this paper, we address first an important methodical problem of this formalism: the choice of the stochastic calculus (Ito or Stratonovich). We prove that both Ito and Stratonovich stochastic integrals give identical results, despite the multiplicative noise present in the stochastic Landau-Lifshitz-Gilbert equation. Discussing correlation properties of Hfl (which is usually assumed to be 6 correlated both in space and time), we point out that finite correlation time and radius of this field can be due not only to physical reasons (heat-bath correlations), but can also arise from the finite-element representation of the continuous problem. Afterwards, we present simulation results concerning the influence of thermal fluctuations on the fast switching of magnetic nanoelements. We consider three typical situations: 1) thermal noise influence on the switching which would happen also in the absence of thermal fluctuations (thermally assisted switching); 2) thermally induced switching of the metastable states; and 3) changing of the switching mode as the consequence of thermal fluctuations.