本論文主要目的是探討鉍鐵氧(反鐵磁層)和鐵白金(鐵磁層)雙層磊晶薄膜在鐵磁層不同沉積溫度下對於交換耦合偏壓的影響。在這篇文章中，我們利用高真空雙靶射頻磁控濺鍍系統鍍製我們的雙層薄膜，鉍鐵氧10奈米且鐵白金10奈米，並利用單晶(111)鈦酸鍶基板使薄膜磊晶成長，同時也有系統的研究鐵白金沉積溫度的影響。我們藉由X光繞射及反射圖譜確認磊晶成長的結構，部分的應變鬆弛在磊晶薄膜中垂直方向上可觀察的到。同步輻射X光繞射的結果可以清楚看到鐵白金在500度有明顯的六軸對稱，且用(002)方位角的掃描清楚的指出薄膜是沿著基板排列磊晶成長。在室溫裡改變不同鐵白金成長溫度下可以得到很大的交換耦合偏壓值54-412奧斯特在(111)鉍鐵氧/鐵白金雙層磊晶薄膜中，但是當FePt 溫度超過保存溫度時，交換耦合偏壓值快速的下降。鉍鐵氧表面形貌對於交換耦合偏壓的影響也同時被研究和探討。

The objective of the study was to investigate effect of ferromagnetic layer growth temperature on exchange bias of BiFeO3/FePt bi-layer epitaxial films. In this paper, we prepared the BiFeO3 (10 nm) / FePt (10 nm) thin films were epitaxially grown on (111) SrTiO3 (STO) single crystal substrates and systemically study effect of deposition temperature of FePt. The formation of epitaxial films structure was confirmed from the x-ray diffraction and (00L) Bragg reflection of x-ray. A slight partial relaxation of out-of-plane strain in epitaxial systems was observed. Synchrotron radiation XRD results display clear sixfold symmetries and (111) FePt/BiFeO3 films by using (002) azimuthal scan, unambiguously indicating that the present samples were epitaxially thin films. Large exchange field (Heb) of 54－412Oe at room temperature were obtained for the epitaxial (111) BiFeO3 (10 nm) / FePt (10 nm) films at different growth temperatures (300 – 700 ºC). With regard to temperature of FePt, there was a large EB value for the samples with FePt temperature at endpoint. As FePt temperature excesses the blocking temperature, the Heb decreases dramatically. The effect of surface morphology of BiFeO3 layers on Heb in the present samples was also investigated.

摘要 i
Abstract ii
Contents iii
Figures Lists vi
Table Lists x
Chapter 1 Introduction 1
1.1 Preface 1
1.2 Application 1
Chapter 2 Literature Review 2
2.1 Origin of magnetism 2
2.2 Type of magnetic materials 2
2.2.1 Paramagnetic 5
2.2.2 Ferromagnetic (FePt) 6
2.2.3 Ferrimagnetic 7
2.2.4 Antiferromagnetic (BiFeO3) 8
2.3 Exchange bias 10
2.4 Theoretical basis of the exchange bias 13
2.4.1 Ideal Interface Model 14
2.4.2 Interfacial AFM Domain Wall Model 15
2.5 Structure and magnetism of FePt 17
2.6 Magnetic Anisotropy 19
2.6.1 Shape anisotropy 19
2.6.2 Magnetocrystalline anisotropy 21
2.7 Type of Perovskite materials (BiFeO3) 21
2.8 Characteristics of BiFeO3 multiferroic material 22
2.8.1 Microstructure 22
2.8.2 Ferroelectric properties of BiFeO3 23
2.8.3 Magnetic properties of BiFeO3 24
2.9 Paper review 26
2.10 Research purpose and motivation 27
Chapter 3 Instrument Description and Experimental Procedures 29
3.1 Samples fabrication 29
3.2 Experimental procedure 32
3.3 Structural Characterization 33
3.3.1 X-ray diffraction (XRD) 33
3.3.2 X-ray reflection (XRR) 35
3.3.3 Field-emission scanning electron microscope (FE-SEM) 37
3.4 Properties Measurement 38
3.4.1 Vibrating Sample Magnetometer (VSM) 38
Chapter 4 Results 41
4.1 Structure of BiFeO3/FePt bilayer thin films 41
4.2 Epitaxial quality of BiFeO3/FePt bilayer thin films 43
4.3 Morphology of BiFeO3/FePt bilayer thin films at different deposition temperature 45
4.4 Measurement of magnetism of BiFeO3/FePt bilayer thin films at different deposition temperatures 49
Chapter 5 Discussion 53
5.1 Ordered-volume fraction 53
5.1.1 Ordered-volume fraction analysis in discussion forums of BiFeO3/FePt bilayer thin films 55
5.1.2 Relation between ordered-volume fraction (f0) and coercivity field (Hc) 57
5.2 Exchange bias 59
5.2.1 Relationship between exchange bias (Heb) and temperature 59
5.2.2 Relation between exchange bias (Heb) and coercivity field (Hc) 62
Chapter 6 Conclusions 63
References 64

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