Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/11019
標題: 鐵/鉑多層膜之結構與磁性質之研究
The Structures and Magnetic Properties of Fe/Pt multilayers
作者: 劉佳怡
Liu, Chia-Yi
關鍵字: Fe/Pt multilayers;鐵/鉑多層膜;order structure;ion beam sputter;magnetic recording media;序化結構;離子束濺鍍;磁記錄媒體
出版社: 材料工程學系所
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摘要: 
本研究利用雙離子束濺鍍系統製備[Fe(X nm)/Pt(Y nm)]Z多層薄膜。XRD與TEM分析結果顯示:初鍍膜Sample A由Fe(a~2.91 Å)及Pt(a~3.91 Å)相所組成,Sample B,C及Sample D均有非序化之fcc FePt相(a~3.7 Å)存在,且Sample D另有L12 Fe3Pt相(a~3.73 Å)存在。其中fcc FePt主要由於鍍膜過程中界面混合所導致,由X-TEM結果得到印證。Fe/Pt多層薄膜之平均晶粒尺寸約為10nm,且其矯頑磁力介於Hc=18 Oe~38 Oe,主要由軟磁相Fe所貢獻。
Fe/Pt多層膜經550 ℃退火6分鐘後均產生L10 FePt(a~3.80 Å, c~3.70 Å)相,主要由於薄膜間互相擴散導致序化結構之形成。退火後樣品之平均晶粒尺寸介於20~60 nm。磁性分析顯示:Sample B具有最大之矯頑磁力(Hc~9200 Oe),與L10 FePt相反應較為完全有關。而Sample D經退火後其矯頑磁力(Hc~160 Oe)遠小於其他樣品,主要由於軟磁相之Fe3Pt生成所致。序化度分析顯示:Sample A具有最高序化度(S~0.9),且隨Pt厚度降低而降低(Sample C:S~0.63)。
Sample B([Fe(15 Å)/Pt(20 Å)]10)於400 ℃以下退火,其結構與初鍍膜相同。當退火溫度於500 ℃以上,L10 FePt結構生成,且其矯頑磁力明顯增加(Hc:6000~9200 Oe)。延長退火時間(20分鐘)或提高退火溫度(600 ℃)導致Hc下降,主要與晶粒成長有關。
Pt底層研究結果顯示:初鍍膜([Pt(20 Å)/Fe(15 Å)]10/Pt(30 nm))之結構與磁性質均接近[Fe(15 Å)/Pt(20 Å)]10之結果。經退火後之樣品於400℃已有L10 FePt之結構生成,且其平均晶粒大小明顯增加為20~40nm。磁性分析方面:400 ℃退火樣品其矯頑磁力增加為Hc~322 Oe,主要與L10開始生成有關,與結構分析結果一致。增加退火溫度至550 ℃,其Hc~4600 Oe較Pt=0 nm者為低,主要由於L12 FePt3相生成所致。
[Pt(20 Å)/Fe(15 Å)]10/Pt(30 nm)經離子轟擊效應方面:由XRD研究結果顯示fcc FePt之繞射峰隨End-Hall voltage增加而有消失之趨勢。且Pt之晶格常數隨End-Hall voltage增加而降低,此顯示結構經離子束轟擊後較為緻密。磁滯曲線分析得知:垂直膜面之飽和磁化場(Hs┴)隨End-Hall voltage增加而降低(Hs┴,70V>12000 Oe,Hs┴,150V~2500 Oe),顯示此樣品在經離子轟擊後具有垂直異向性之性質。
樣品經550 ℃退火後,L10 FePt相與L12 FePt3相(70V樣品)隨End-Hall voltage增加而相分離為(Fe+Pt)相(150V樣品),150V樣品其結構仍與初鍍膜(150V)者相同(Fe+Pt)。矯頑磁力隨End-Hall voltage增加而降低,顯示離子束轟擊效應會破壞序化相L10 FePt之生成。

The structures and magnetism of [Fe(X nm)/Pt(Y nm)]Z multilayers were investigated. XRD and TEM analysis indicated Sample A consisted of Fe (a~2.91 Å) and Pt (a~3.91 Å) phases whereas a disordered fcc FePt (a~3.7 Å) phase was found in Sample B, C, and D due to intermixing at the interfaces. In addition, Sample D consisted of L12 Fe3Pt (a~3.73 Å) phase. The average grain sizes of Fe/Pt multilayers are about 10 nm. All as-deposited samples exhibiting small coercivities (Hc~ 18 Oe to 40 Oe) are mainly from the magnetically soft Fe phase.
The L10 FePt (a~3.8 Å, c~3.7 Å) phases formed after annealing at 550 ℃ for 6min. The grain sizes range from 20 to 60 nm in these annealed samples. The maximum coercivity was observed in Sample B (Hc~9.200 Oe). The small coercivity of Sample D (Hc~ 160 Oe) is due to formation of soft Fe3Pt phases. Sample A exhibited highest ordering parameter (S~0.9), and S decreased with reducing Pt thickness (Sample C: S~ 0.63). Extending annealing time (20 min) or increasing annealing temperature (600 ℃) resulting in decrease in coercivity is associated with grain growth.
The addition of Pt underlayer has shown that the structures and magnetic properties of ([Pt (20 Å)/Fe (15 Å)] 10/Pt (30 nm)) are similar to those of ([Fe (15 Å)/Pt (20 Å)]10). However, the temperature at which L10 FePt phases formed was reduced to 400 ℃ with addition of Pt underlayer. Further increasing the annealing temperature to 550 ℃, the smaller coercivity (Hc~ 4600 Oe) is due to formation of L12 FePt3 phases.
Effects of ion-beam bombardment have shown that the fcc FePt phases tend to disappear with increasing End-Hall voltage (VEH). The lattice constant of Pt decrease with increasing VEH indicates the Pt structures are more compact after bombardment. In addition, the out-of-plane saturatation field (Hs┴) decreases with increasing VEH (Hs┴,70V> 12000 Oe, Hs┴,150V~ 2500 Oe) indicating the perpendicular anisotropy by ion-beam bombardment. At VEH= 150V, the formation of L10 FePt phases and L12 FePt3 phases were suppressed even annealed at 550 ℃.
URI: http://hdl.handle.net/11455/11019
Appears in Collections:材料科學與工程學系

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