不同傾斜沉積角度對於鉑/鈷/鉑系統之磁性性質研究與探討

Abstract

在所有種類之記憶體中，以自旋軌道間力矩為驅使動力之磁性記憶體(SOT-MRAM) ，由於其在寫入速度快速及功耗少等優點，乃被眾人視為一前途看好之結構設計。然而，在賈拉辛斯基 - 守屋交互作用 (Dzyaloshinskii-Moriya interaction) 的限制下，若要以施加電流方式，使其磁性狀態改變，我們必須再另外施加一同電流方向的磁場，使之微觀狀態下的對稱性破壞，在此限制下，此記憶體之實際運用便陷入困難。不過，已有幾種針對此令人棘手問題的方法被發展出來，例如: 利用反鐵磁交換耦合 (鐵磁/反鐵磁結構)，利用幾何形狀上不對稱結構 (楔形結構) 等方法。然而上述某些方法之試片製程複雜，甚至有些方法使用的材料會和現今主流之互補式金屬氧化物半導體 (CMOS) 系統不相容。於此篇工作中，我們使用常見的鉑/鈷/鉑三層結構進行實驗，並且我們以簡單且有效率的方法來製作不須加場就可進行翻轉的試片。再者，我們以掃描入平面之外加場，來觀察磁滯曲線移動實驗實驗來確認我們對於實驗的假設。我們同時確認下層之鉑，對於正在研究之磁性性質，扮演非常重要的角色。最後，我們以一個簡單的模型來解釋關於該試片為何可以進行無場翻轉的機制。

Among all kinds of memory devices, the magnetic random-access memory in the application of spin-orbit torque (SOT-MRAM) is one of the promising design for efficient data writing and lower power consumption. However, the existence of Dzyaloshinskii-Moriya interaction (DMI) restrict the practical utilization of SOT-MRAM. To achieve deterministic switching by electrical current flow, we must exert an external magnetic field along the current to break symmetry. Several methods have been developed to solve this tough problem, such as the assistance of antiferromagnetic exchange coupling (FM/AFM structure), the manufacture of geometrically asymmetric structure (wedge-shape structure), etc. Some of them are complicated in fabrication. Even a part of them is incompatible with the current CMOS system. In this work, we use common Pt/Co/Pt trilayer in experiments and introduce a simple and efficient method for fabricating devices capable for field-free switching. Subsequently, we use loopshift measurement with angle-scan in-plane field to confirm our hypothesize. Meanwhile, we also confirm that the bottom Pt layer of trilayer structure plays a crucial role for deterministic field-free switching. Finally, a simple model is established to explain the exact mechanism of our samples.