Spin Current Tunneling through an Al2O3 Oxide Barrier Investigated by Spin Pumping Effect

非揮發性記憶體憑藉著節能的需求快速的發展，而自旋電子學也因此迅速的崛起，而在此相對新興的領域中若要有良好的應用元件，則自旋流的產生機制則扮演著相當重要的角色，其中自旋幫浦效應變是其中一個能夠有效產生純自旋流的方法。然而經過了許多的研究發現，表面的特性對於其產生占著格外重要的因素，因此了解氧化界面及位能壁壘是否仍可以有效的傳遞自旋流便是一個相當重要的基石。 於此首先以白金/鎳鐵合金系統用於展示我們的的系統和利用反轉自旋霍爾效應的量測與電壓的關係驗證我們的系統穩定度，接著我們以白金/氧化鋁/鎳鐵合金系統作於我們的實驗主體，並且量測電流與電壓關係驗證壁壘其為一個可以表現出電流電壓非線性的良好壁壘，此一電性特徵表示電子是藉由量子穿隧效應作為主要傳輸機制，而後置於鐵磁共振腔中量測其反轉自學霍爾效應的電壓，而實驗結果仍然能夠量測到其電壓意即表示自旋流的確有抵達白金層，而此即為介面傳輸上的一個突破，目前為止並無實驗上直接的證據自旋流能意以電子攜帶方式傳過氧化介面。外加微波功率的依存性實驗結果為線性關係與單純白金/鎳鐵合金系統相同。而角度的依存性就趨勢上而言是與反轉自旋霍爾效應的預測成正向關係的。但我們仍能看出現了對稱性上的破缺，我們仍需要更深入的研究。全文最後討論了自漩流可能的傳輸機制，由於目前主流的自旋流傳輸機制有自旋波以及自由電子攜帶自旋方式傳遞，而我們討論了此處共振場的大小以及微波吸收頻譜的特性，可以推測此處仍是以電子攜帶自旋方式傳遞，又我們驗證了電子是以量子穿隧方式走過壁壘，所以此處自旋極有可能也是以穿隧方式越過壁壘。Spintronics proliferate quickly in the recent years and spin current generation would be one important issue for spintronic application. Spin pumping effect is one method to generate pure spin current. For further researches, the interfacial properties is an important issue for spin transport and oxide interface and oxide barrier was intensively researched by many groups. However, there were still none focus on whether spin could tunnel through a barrier with ferromagnetic metal layer. This would be an important issue for the following research. First Pt/Py system was used as a standard demonstration for us and also tested for stability of our system by thickness dependence of platinum. The results reveal the insight of thickness dependence by means of inverse spin Hall effect and well-controlling deposition rate. The inverse spin Hall voltage still could be measured in Pt/Al 2 O 3 /Py system whose oxide barrier was confirmed by non-linear I-V feature. Checking the power dependence and angle dependence of that inverse spin Hall voltages was done as well. The power dependence is linear which is the same as our expectation and there is a discussion about the asymmetry of angle dependence. At last there would be some further discussion about transport properties. There are two well-accepted transport mechanism for spin—charge carriers with spin and spin waves. From the I-V measurement, the dominated electric transport mechanism of the system might still be the tunneling effect so the transport mechanism of spin current in this system is probably carrier by tunneling electron carriers