本研究中，我們使用改變後退火效應來觀察濺鍍製程鎳鐵薄膜(Ni84Fe16)系列的磁性阻尼行為，濺鍍薄膜厚度範圍為10 nm ~ 100 nm，而鎳鐵薄膜後退火過程在真空度約10-7 torr中進行，達到標的溫度(範圍由室溫至700 ℃)後定溫30分鍾，自然冷卻取出。利用網路分析儀配合傳輸線和覆晶量測法(flip-chip)達到鐵磁共振吸收譜線的量測。而磁性阻尼常數α提取的部份，當達共振吸收頻率時，由掃場式鐵磁共振量測法測量出的吸收峰譜線，可以其半寬值與共振頻率線性擬合換算出阻尼常數，擬合頻率範圍由1GHz~4.5GHz。
　　在改變後退火溫度(Ta)的樣品測量下，可明顯觀察到阻尼常數α會隨溫度(Ta)的提升而出現兩段阻尼增進的趨勢，第一段是退火溫度在250℃前的低溫退火區段，第二段則是高於250℃的高溫退火區段。為解釋阻尼常數α隨退火溫度增加而增進的機制，在樣品分析中，使用了掃描式電子顯微鏡(SEM)和X光繞射分析儀(XRD)，觀察出在高溫後退火區段有晶粒成長(Grain growth)及內部缺陷消除現象，但也由於此原因表面過大的粗糙度變化增加了巨觀的表面缺陷，所以在高溫後退火區段的樣品，阻尼增進可能的主要貢獻來自於雙磁子散射機制；另一方面，呈現出平坦膜面與高密度缺陷的低溫退火區段樣品，其阻尼增進則推測來自與電子散射機制。
　　由於雙磁子散射現象是外加場的函數，隨外加場變大，雙磁子效應明顯，也就是增加阻尼的效應，所以我們利用掃頻式鐵磁共振量測訊號下的阻尼常數與外加場關係趨勢中，可驗證高溫區段的阻尼增進主要由雙磁子效應所提供，而低溫退火區段主要由電子散射效應所提供。

In this study, we investigate the effect of post-annealing on magnetization damping in sputtering deposited NiFe thin films. The film thickness is ranged from 10 nm to 100 nm. Thin films were deposited at room temperature and a subsequent post-annealing was performed in vacuum better than 10-6 torr from room temperature to 700 0C for 30 minutes. The ferromagnetic resonance (FMR) spectrum was measured with a vector-network-analyzer (VNA) by flip-chip technique. Magnetization damping coefficient, α, was extracted from the linear fitting of dependence of absorption linewidth of field-scan spectrum on resonance frequency. The frequency range of the FMR measurement is from 1 GHz to 4.5 GHz.
The dependence of α on post-annealing temperature (Ta) indicates two increments in magnetic damping. One is at Ta lower than 250˚C, where α increases with the decrease of the Ta. Another damping enhancement is at Ta higher than 250˚C; contrary to the low Ta region, α increases with the increase of the Ta. Results of structural analysis including scanning electron microscopy (SEM) and X-ray diffractometry (XRD) reveal that high temperature annealing induces significant grain growth and defect elimination, resulting in large surface roughness of the films. This infers that the damping enhancement in those high-Ta annealed films may originate from the mechanism of magnon-magnon scattering. On the other hand, the flat surface and high density of defects suggest that the increase of α may come from the enhancement of electron scattering. The two different mechanisms show distinct external field dependence of α: α under two-magnon scattering is proportional to external field; α enhanced by electron scattering is independent with external field; we thus use this difference to identify them. Dependence of α on external field was extracted from the frequency-scan spectrum. The results confirms that the damping enhancement at high Ta arises from two-magnon scattering mechanism and at low Ta are caused by enhanced electron scattering effect.

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