近年來，由於新穎磁性元件的高應用性，吸引了許多相關的研究，這其中包含了圖樣式磁紀錄媒體、磁性記憶體、以及磁區壁元件。但當為了高儲存密度而微縮化這些磁性元件的體積時，鐵磁層的熱穩定性也會跟著下降，這對於長期的資訊儲存是一項嚴重的考驗，具有垂直異向性的鐵磁材料因此而被引入到這些磁性元件中，解決小體積時的熱穩定性的問題。除此之外，垂直異向性的鐵磁材料也能幫助降低自旋傳輸翻轉時的能障，使得自旋傳輸翻轉的效率增加。因此如何整合具有垂直異向性的鐵磁材料至磁性元件中便是一個重要的課題。鈷鉑多層膜是一種具有垂直異向性的鐵磁材料，因為其容易製造以及其垂直異向性可以大範圍調整的特性，而被應用於製作具垂直異向性鐵磁層之磁性元件的原型中。但由於其垂直異向性來自於鈷與鉑的介面，因此其磁性質容易受到熱處理而影響，不易控制。此外，鉑具有很強的自旋軌道耦合使自旋流消失，以及鈷鉑多層膜具有很高的磁阻尼係數，這兩項因素使得鈷鉑多層膜難以用自旋傳輸的方式翻轉，從而限制了鈷鉑多層膜在磁性元件的適用性。

有鑑於此，在本文中，我們將聚焦鈷鉑多層膜在實際應用的兩個主要問題中: (1)熱處理過程中的磁性質控制，以及(2)藉由電流翻轉操控磁矩。我們首先研究鈷鉑多層膜的磁性在快速退火時的變化，我們發現此磁性質的變化與薄膜應力的釋放有很強的關聯性，藉由控制微區的應力釋放，我們可以達成所謂”磁圖樣化”的技術來控制微區磁性質。另外，我們也試圖使用電的方式來翻轉鈷鉑多層膜的磁矩，我們先評估了鈷鉑多層膜的自旋軌道力矩效率，發現其與鈷鉑之介面以及鈷鉑多層膜的層數有關。同時我們也成功展示了利用自旋軌道力矩來翻轉鈷鉑多層膜的磁矩，但當多層膜層數增加時，多磁區狀態的形成取代了磁矩完整的翻轉，藉由介面的改質，我們可以在多層膜層數增加時，抑制多磁區狀態的形成。而就由這些工作，我們相信鈷鉑多層膜在真實原件上的適用性可以被改善。

There has been a great interest recently in novel magnetic devices such as magnetic patterned media, magnetic random access memory, and magnetic domain wall devices. However, with the scaling-down of the magnetic devices for the higher storage density, the degradation of thermal stability of the ferromagnetic layers with cell size becomes a severe issue for long-term storage and preservation. Therefore, the ferromagnetic materials with perpendicular magnetic anisotropy (PMA), which provides the better thermal stability due to the higher effective anisotropy, have been introduced to those novel magnetic devices for solving the thermal stability issue. Besides, PMA materials may also reduce the energy barrier for the spin-transfer-torque switching of the magnetic moments, leading to a more efficient reversal. Consequently, to integrate the PMA materials with those magnetic devices is a very important issue for pursuing better performance and smaller devices. The Co/Pt multilayers (MLs) is a kind of PMA materials, where its PMA is originated from the interfacial anisotropy of Co/Pt interfaces. Because the Co/Pt multilayers can be easily fabricated with tunable PMA, it has been widely applied to demonstrate the magnetic devices with PMA. Nevertheless, the magnetic properties of the Co/Pt multilayers are sensitive to the thermal process, which is hard to precise control the magnetic properties. Besides, due to the severe spin depolarization of Pt and the high damping constant, the Co/Pt multilayers is hardly reversed by spin-transfer torque, which limited the adoptability of Co/Pt MLs in real applications.

In this work, we try to solve the problems of Co/Pt MLs in real applications. Two main directions have been focused: (1) precise control of the magnetic properties with the thermal process and (2) manipulation of the magnetization switching by electrical means. We first investigated the magnetic properties modification with rapid thermal annealing. We found the evolution of magnetic properties with thermal process is strongly correlated with the stress relaxation process. By controlling the stress relaxation in local regions, we can locally control the magnetic properties to achieve the so-called magnetic patterning. On the other hand, to find an electrical means for switching the Co/Pt multilayers, we evaluate the spin-orbit-torque efficiency of the Co/Pt multilayers. We found the spin-orbit-torque efficiency of the Co/Pt multilayers is strongly affected by the interface conditions and scaling with the repeating numbers of the multilayers. We also demonstrate the spin-orbit-torque switching on Co/Pt multilayers, where the multi-domain formation is a problem to obstruct the bipolar magnetization switching when repeating layer number is large. By engineering the interfaces, the multi-domain formation can be suppressed to achieve a completely switching with higher repeating layer numbers. As a result, our findings may improve the adoptability of Co/Pt multilayers in real applications.

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