MgO/CoFeB/Ru/CoFeB/MgO從水平式到垂直式之介面交換耦合

The Interface Exchange Coupling From In-plane to Perpendicular Configuration in MgO/CoFeB/Ru/CoFeB/MgO

陳建璋(Chien-Chang Chen)

指導教授 ： 陳恭

國立中正大學/理學院/物理學系/碩士(2013年)

摘要

本實驗主要利用磁控濺鍍系統(sputter)成長人工反鐵磁結構MgO(1nm)/CoFeB(1.2nm)/Ru(x nm)/CoFeB(1.2nm)/MgO(1nm)來探討其交換耦合以及退火效應。
　　全結構在退火前為水平異向性，兩層鐵磁層隨著Ru厚度的增加呈現平行-反平行耦合振盪的現象，週期約為1.2 nm。
　　以Ru為間隔層的人工反鐵磁結構能夠退火達430度，有助於未來磁阻率的提升，而異向場在適合的退火溫度範圍內最大可達5000 Oe，藉由退火改善MgO/CoFeB介面來提高異向能，使得將來在製作成元件時有助於熱穩定性的提升。
　　退火後，磁易軸垂直膜面，耦合能隨著Ru厚度增加有振盪的現象，耦合能做大值為0.26 erg/cm2。在耦合能振盪曲線波峰的位置，磁滯曲線呈現反平行耦合的樣貌，與退火前類似。然而，在振盪曲線波谷的位置，卻不像退火前呈現單一方正磁滯曲線的樣貌，而是呈現翻轉場很小、殘餘磁化量為零的現象，顯示這當中不單只有耦合現象，還必須考慮其他，例如：磁疇的因素。

關鍵字：鈷鐵硼、垂直異向性、人工反鐵磁

關鍵字

人工反鐵磁 ； 垂直異向性 ； 鈷鐵硼

並列摘要

In this study, we fabricate a series of synthetic antiferromagnetic structures with Ru spacer by sputtering system : Ta(10)/MgO(1)/Co20Fe60B20(1.2)/Ru(x)/Co20Fe60B20(1.2)/MgO(1)/Ta(1), x=0.6~3, unit : nm.
The oscillatory exchange coupling via Ru spacer is observed before and after annealing process. However, the magnetic easy axis is in the plane before annealing while the magnetic easy axis becomes perpendicular to the plane after annealing. For in-plane anisotropic films, the oscillatory period of ~ 1.2 nm and maximum coupling strength ~ 0.54 erg/cm2 are revealed. For perpendicular anisotropic films, the magnetic hysteresis curves in antiparallel-coupled states show similar spin-flop transitions but with weaker coupling strength ~ 0.26 erg/cm2. However, the magnetic hysteresis curves in parallel-coupled states show stripe-domain-like characteristic in which both remanence and coercivity vanish at H ~ 0.
Moreover, a detailed study of the annealing is also carried out. The antiferromagnetic structures with a thinner Ru spacer can be annealed over 400oC and these film maintain their characteristics. The saturation field can reach ~ 5 kOe, corresponding to anisotropy energy ~ 3×106 erg/cm3, after annealing 430oC.

Keywords：CoFeB, perpendicular magnetic anisotropy, synthetic antiferromagnet.

並列關鍵字

synthetic antiferromagnet ； perpendicular magnetic anisotropy ； CoFeB

參考文獻

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