- 學位論文
底層對FePd薄膜磁性之影響
Effect of underlayer on the Magnetic properties of FePd thin films
摘要
由於面心正方結構的L10-FePd薄膜具有高磁晶異向性能、飽和磁化量和居里溫度，故近年來倍受關注。雖然L10-FePd的本質磁特性與其他的L10合金系相近，但目前研究的結果顯示FePd的外質磁性較其他L10合金差，尤其是矯頑磁力。 本實驗以射頻磁控濺鍍法於室溫下製備50 nm Fe100-xPdx薄膜(x=34-50)於康寧1737玻璃基板上，並使用快速升溫退火爐在(Ta = 500 - 750 oC)持溫10分鐘做熱處理。Fe100-xPdx薄膜(x=34-50)經過後退火處理後皆呈現水平磁異向性。隨著後退火溫度之提高，其結構漸從A1相轉變為L10相，因而提高其矯頑磁力；但當退火溫度上升至750 oC時，FePd薄膜從L10相轉為fcc結構，導致其矯頑磁力大幅降低。此外，其水平矯頑磁力隨著Fe的含量減少而上升，從Fe66Pd34之0.15 kOe上升至Fe50Pd50的2.3 kOe。 再者，亦研究了不同退火溫度對不同底層(Mo、Nb、W)對磁性的影響。結果顯示，隨著退火溫度的增加，僅有FePd/W之薄膜矯頑磁力有明顯的上升。矯頑磁力最高值為3.8 kOe，出現在FePd/3 nm W薄膜經700 oC之後退火。不過，使用較厚之W底層於高溫後退火下，使W底層與FePd層較嚴重之相互擴散，導致其矯頑磁力大幅下降。此外，W底層可有效地促進FePd膜序化並細化L10晶粒，因而可提高其矯頑磁力與磁能積，分別由FePd薄膜之2.3 kOe及5.3 MGOe提升至FePd/3 nm W之3.8 kOe及8.4 MGOe。本實驗結果驗證了加入W底層可有效地提高FePd薄膜之硬磁性。
並列摘要
FePd films with the tetragonal L10 phase have attracted considerable attention due to high magnetocrystalline anisotropy, saturation magnetization, and Curie temperature. Although these magnetically intrinsic properties for L10-FePd phase are comparable to other L10 phase, the studied L10-FePd films exhibited inferior extrinsic properties up to now, especially for coercivity. In this work, FePd thin films with 50 nm in thickness were sputtered on Corning 1737 glass substrates at RT. Subsequently, FePd films were annealed at (Ta) 500-750 oC for 10 min, by rapid thermal annealing. The structure and magnetic properties of Fe100-xPdx thin film (x=34-50) on the glass substrates are studied. Fe100-xPdx films(x=34-50) deposited at room temperature followed by a rapid thermal annealing exhibits in-plane magnetic anisotropy. The phase transformation from the A1 to L10 with the increasing Ta in FePd films enhances its coercivity. Nevertheless, the L10 phase is gradually transformed into fcc phase at higher Ta = 750 oC, largely reducing the coercivity. Besides, the in-plane coercivity increases with decreasing Fe content from 0.15 kOe for x = 34 to 2.3 kOe for x = 50. Furthermore, effect of underlayer(Mo, Nb, W) on magnetic properties of FePd films are also studied. The coercivity is increased with increasing Ta and reached the maximum value of 3.8 kOe at 700 oC for FePd/3 nm W film. However, the coercivity is reduced for the films with thicker t = 10 nm annealed at higher Ta, which might be resulted from more severe interdiffusion at the interface between FePd and W layer. In addition, W underlayer is helpful in refining the grain size of L10 phase and thus enhancing both Hc and (BH)max of FePd films from 2.3 kOe and 5.3 MGOe to 3.8 kOe and 8.4 MGOe, respectively. The results of this study demonstrate the use of W underlayer could effectively improve permanent magnetic properties of FePd films.