磁芯材料與磁穿隧接面中高頻磁化動態之微磁模擬

Abstract

在現代與新興電子系統中，利用千兆赫茲（GHz）頻率的磁性元件至關重要。以積體電感為例，它可以儲存磁能，是無線通訊系統中不可或缺的元件。隨著系統對更高操作頻率與更小元件面積的需求日益提升，電感的設計也需要更加優化，而磁芯材料的導入正是一項可行的解決方案。此外，磁阻式隨機存取記憶體作為一種新穎的非揮發性記憶體，也經常透過GHz頻率範圍內的鐵磁共振（FMR）量測，來分析其中磁穿隧接面（MTJ）的特性。在此背景下，微磁模擬因具備解析奈米尺度磁性材料在高頻行為的能力，已成為推動相關技術發展的重要工具。 本論文運用微磁模擬來探討磁性材料在高頻下的共振行為，藉此連結材料層級的物理響應與實際元件的操作效能。對於電感中的磁芯材料，本研究系統性的分析粒徑、飽和磁化量、阻尼常數與幾何結構等變化，對磁奈米粒子（NP）與奈米線（NW）在有效磁導率、共振頻率及損耗表現上的影響。模擬結果顯示，雖然NP可藉由設計達到較高的共振頻率，但磁導率較低；相較之下，NW則在共振頻率與磁導率之間取得較好的平衡，因而更適合作為高頻電感的磁芯材料。另一方面，MTJ的模擬中，自由層與固定層呈現出不同的FMR訊號，其中自由層具有明顯的單一共振峰，固定層則出現不同模態的兩個較弱訊號。而在自由層無明顯響應的低頻區段，提升輸入功率可使固定層的訊號更容易被觀察到，對於產線上的量測應用具有參考價值。綜合上述，本研究有助於建立高頻磁性材料與元件的設計與量測架構。

Magnetic devices leveraging GHz frequencies play a key role in modern and emerging electronic systems. For instance, integrated inductors, which store magnetic energy and are indispensable in wireless communication systems demanding higher frequencies and smaller footprints, require careful design to ensure optimal performance, potentially including the use of magnetic cores. Furthermore, magnetoresistive random access memory, a novel type of non-volatile memory based on magnetic tunnel junctions (MTJs), also undergoes extensive characterization in this frequency regime through techniques such as ferromagnetic resonance (FMR) to evaluate magnetic properties and device performance. A critical challenge in advancing these technologies lies in controlling and tailoring their complex magnetization dynamics. In this context, micromagnetic simulations have become an valuable predictive tool, offering detailed insight into the dynamic behavior of magnetic materials at the nanoscale under GHz-frequency conditions. In this thesis, micromagnetic simulations are used to explore these dynamics, focusing on resonance phenomena and aiming to bridge fundamental material-level responses with device-level performance. Regarding magnetic core materials for inductors, the research systematically examines how variations in parameters, such as particle size, saturation magnetization, damping constant, and structural geometry, affect the effective permeability, resonance frequency, and loss characteristics of magnetic nanoparticles (NPs) and nanowires (NWs). Findings indicate that while NPs can be engineered for higher resonance frequencies, they often suffer from reduced permeability. NWs, however, demonstrate a more favorable trade-off, positioning them as superior candidates for high-frequency inductors. For MTJs, simulations characterize distinct FMR signals from free layer and pinned layer. The free layer exhibits a strong single peak, while the pinned layer shows two weaker peaks associated with different dynamic modes. In low-frequency regimes where the free layer signal is absent, increasing the applied power enhances the detectability of the pinned layer signal, providing practical guidance for in-line characterization. These insights contribute to a comprehensive framework for designing and characterizing magnetic materials and devices operating at high frequencies.