Liang Cheng-Yen, Keller Scott M, Sepulveda Abdon E, Bur Alexandre, Sun Wei-Yang, Wetzlar Kyle, Carman Gregory P
Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095, USA.
Nanotechnology. 2014 Oct 31;25(43):435701. doi: 10.1088/0957-4484/25/43/435701. Epub 2014 Oct 7.
Micromagnetic simulations of magnetoelastic nanostructures traditionally rely on either the Stoner-Wohlfarth model or the Landau-Lifshitz-Gilbert (LLG) model, assuming uniform strain (and/or assuming uniform magnetization). While the uniform strain assumption is reasonable when modeling magnetoelastic thin films, this constant strain approach becomes increasingly inaccurate for smaller in-plane nanoscale structures. This paper presents analytical work intended to significantly improve the simulation of finite structures by fully coupling the LLG model with elastodynamics, i.e., the partial differential equations are intrinsically coupled. The coupled equations developed in this manuscript, along with the Stoner-Wohlfarth model and the LLG (constant strain) model are compared to experimental data on nickel nanostructures. The nickel nanostructures are 100 × 300 × 35 nm single domain elements that are fabricated on a Si/SiO2 substrate; these nanostructures are mechanically strained when they experience an applied magnetic field, which is used to generate M vs H curves. Results reveal that this paper's fully-coupled approach corresponds the best with the experimental data on coercive field changes. This more sophisticated modeling technique is critical for guiding the design process of future nanoscale strain-mediated multiferroic elements, such as those needed in memory systems.
传统上，磁弹性纳米结构的微磁模拟依赖于斯托纳 - 沃尔法斯模型或朗道 - 利夫希茨 - 吉尔伯特（LLG）模型，假定应变均匀（和/或假定磁化均匀）。虽然在对磁弹性薄膜进行建模时，均匀应变假设是合理的，但对于较小的面内纳米级结构，这种恒定应变方法变得越来越不准确。本文提出了旨在通过将LLG模型与弹性动力学完全耦合来显著改进有限结构模拟的分析工作，即偏微分方程本质上是耦合的。将本手稿中推导的耦合方程，以及斯托纳 - 沃尔法斯模型和LLG（恒定应变）模型与镍纳米结构的实验数据进行比较。镍纳米结构是在Si/SiO₂衬底上制造的100×300×35 nm单畴元件；当这些纳米结构受到外加磁场作用时会产生机械应变，该外加磁场用于生成M与H曲线。结果表明，本文的完全耦合方法与矫顽场变化的实验数据最为吻合。这种更复杂的建模技术对于指导未来纳米级应变介导的多铁性元件（如存储系统中所需的元件）的设计过程至关重要。
