鐵磁薄膜誘發富勒烯XMCD之磁性探討

Abstract

本實驗內容主要探討在鐵、C60多層膜結構於Au/Al2O3基板上，經軌域混合後誘發C60磁性，並從X光的圓偏振二向性現象量測來自於C60有極大的訊號。 我們的樣品主要結構是鐵、C60多層膜，重複堆疊沉積於Au/Al2O3基板，使用的鍍膜裝置為電子束熱蒸鍍於超高真空系統內，利用磁光柯爾效應(MOKE)進行一系列的磁性量測，發現其磁易軸方向為平行於樣品，而在X光的圓偏振二向性現象(XMCD)發現碳的K edge有極大的自旋極化率，並且連帶影響到鐵本身在L2,3-edge的極化率，這些變化會依據C60的厚度而有所改變，根據此結果，我們將探討鐵與C60是否有耦合的情況發生，從拉曼光譜中的特徵峰位移以及D-band訊號的改變確認鐵和C60之間有介面耦合的情形發生，之後透過穿透式電子顯微鏡(TEM)得知樣品橫截面構造以及厚度，以及掃描電子顯微鏡(SEM)得知樣品表面結構，這些實驗結果顯示了鐵和C60之間的介面耦合。

In this study we report on the hybridization-induced large X-ray magnetic circular dichroism (XMCD) of carbon in Fe-C60 composite thin films. The samples were prepared by repeating sequential deposition of C60 and Fe for three times on Au/Al2O3(0001) substrate, using e-beam heated evaporators in an ultrahigh vacuum (UHV) chamber. The Fe-C60 composite thin films were investigated by magneto-optical Kerr effect (MOKE), X-ray magnetic circular dichroism (XMCD), transmission electron microscopy (TEM), and Raman spectroscopy. The composite thin films revealed in-plane anisotropy, and the remanence became weak and the magnetic coercivity decreased with C60 coverage. The considerable XMCD signal was observed at the K-edge of carbon, and the corresponding XMCD revealed a relatively small signal at Fe L2,3-edge. Asymmetry the XMCD spectrum, we observed that the carbon will induce strong XMCD signal. The C60 peak was observed at the pure C60 sample in Raman spectrum. It indicated the C60 growing was stable. After Fe deposition, the peak was shifted and D-bond peak signal was increased relatively. TEM analysis revealed the total thickness of this Fe-C60 composite thin film was approximately 15 nm, and the Fe signal was existing in carbon layer by elemental analysis. These observations indicate the hybridization-induced magnetic moment in carbon and possible reduction of magnetization in Fe. The considerably magnetized carbon-based material will be valuable in future application of organic spintronics.