π共軛分子苝四甲酸二酐在基於釔鐵石榴石以及鎳鐵合金的自旋幫浦系統中的自旋傳輸性質

Abstract

近十幾年來，自旋電子學成為了一個新興的領域，許多的材料被廣泛的研究並且運用在自旋閥、自旋幫浦系統以及磁性穿隧接面等元件中，其中，有著π共軛系統的有機分子因結合良好的載子傳輸特性與較低的自旋軌道耦合、低成本和柔韌性被視為相當具有潛力的材料，儘管這個領域發展迅速，但自旋在有機材料中的傳輸機制仍然在爭論中，這篇論文中，我們藉由改變自旋幫浦系統中的鐵磁材料，使得苝四甲酸二酐(PTCDA)表現出不同的自旋傳輸性質，實驗中使用的是常見的雙層及三層結構，鈀被鍍在上層作為自旋感測器，而PTCDA則被夾在鐵磁層與重金屬層之間，當我們使用鎳鐵做為自旋源時，自旋流如預期地穿過PTCDA並且經由逆自旋霍爾效應轉換為可被偵測的電壓，然而，當我們將鎳鐵換成釔鐵石榴石(YIG)時訊號消失了，藉由分析吉伯阻尼常數，我們可以進一步知道PTCDA改變了系統的自旋混合電導，這個結果使我們對於有機材料的自旋傳輸機制有更多的了解。

In the past few decades, spintronics becomes a novel field and many materials have been widely studied in spin valve, spin pumping system, and magnetic tunnel junction. Among them, π –conjugated molecules are regarded as a potential material due to favorable carrier transport properties, low spin-orbital coupling, low-cost, and mechanical flexibility. Although this field has rapidly grown, the spin transport mechanism in organic material is still under debate. In this thesis, we demonstrate the different spin transport behavior of Perylene-3,4,9,10-tetracarboxylic dianhydride(PTCDA) in spin pumping systems by changing the ferromagnetic material. We used general bilayer and trilayer structures. Pd was deposited as the spin detector on the top layer and PTCDA act as barrier layer inserted between ferromagnetic layer and heavy metal. When permalloy is used as spin source, spin current can pass through PTCDA layer as expected and the inverse spin Hall voltage convert from spin current can be measured. However, if we replace permalloy with YIG, the spin pumping signal disappear. By analyzing Gilbert damping constant, we further resolve the change of spin mixing conductance after inserting PTCDA. The results will enable us to know more about the spin transport mechanism in organic material.