利用圓偏極化脈衝雷射對磁光材料進行超快磁反轉是近年來熱門領域，各國研究團 隊爭相投入研究，期待能開發出翻轉時間更快、飽和磁場更大、且永久翻轉等新材料， 並期望未來能用量子同調控制來解析其物理機制。 我們預期主宰磁光材料的翻轉機制為磁光巴涅特效應(magneto-optical Barnett effect)。傳統的巴涅特效應為一磁性材料繞著自身的軸旋轉後會開始磁化；所以利用圓 偏極化超短脈衝雷射作用在磁光材料上，我們可以把雷射和薄膜間的交互作用看成在聚 焦的薄膜上產生一向上或向下的磁場，薄膜為抵消雷射光產生的磁場，故產生一反向的 磁場，此機制稱磁光巴涅特效應。 本論文著重於Gd22Fe74.6Co3.4 此比例的磁光材料，預期它能在皮秒(picosecond)的 時間內進行永久的翻轉，並以飛秒時間的尺度對其進行動態時間解析。 本論文的第一章先簡介超快磁轉化的研究發展和各個理論模型；第二章介紹各種永 磁、稀土材料的特性和參數；第三章介紹本實驗室的雷射系統，和為研究磁性材料所架 設的脈衝雷射鍍膜系統(PLD)；第四章主要是介紹PLD 鍍膜的步驟，包括實驗架設和改 進、參數設定；第五章則是磁性材料的量測系統和量測方法；第六章是我的量測結果和 未來預計將做的改進和研究。 Using circularly polarized femtosecond laser pulses to manipulate ultrafast magnetization switching in magnetic material is recently a active topic in reaserch. Many groups all around the world eagerly focus on this topic, expecting to develope novel materials that possess faster switching speed, stronger saturation magnetization. We expect that we will use quantum coherence control to figure out it's mechanism. We referred to as magneto-optical Barnett effect must be at work. Traditionally, Barnett effect is the magnetization of an uncharged body when spun on its axis. Therefore, by using circularly polarized femtosecond laser pulses on magnet-optic material, we can regard interaction between laser and thin-film up and down magnetic field focusing on the thin film. Thin film generated a reverse magnetic field to neutralize the field induced by laser. This mechanism is called magneto-optical Barnett effect. This thesis focus on thin film samples Gd22Fe74.6Co3.4, expecting it can perform magnetization reversing at picosecond time-scales. We also want to analyze ultrafast switching mechanism under picosecond time-scales. First chapter of this thesis briefly introduce recent research progress on Ultrafast magnetization Switching and all the related theory models. Permanent magnetized and Rare-Earth material will be discussed in chapter 2. Laser system and PLD thin film deposition system in our lab will be reviewed in chapter 3. PLD deposition prcedures ,including experiment setup, improvement and argument seting are reviewed in chapter 3. Details of the magnetic material measuring system and measuring method will be discussed in chapter 4. My measurement data and future improvement on research is included in chapter5.
