臺灣博碩士論文加值系統

磁性材料早已廣泛應用於日常生活，尤其是磁感應器（Sensor）。此外，隨著製程的進步，許許多多的磁性應用發展潛力，更是逐一實現。其中最具想像空間的，就是MRAM（Magnetic Random Access Memory）的應用。MRAM具有許多現行DRAM（Dynamic Random Access Memory）難以望其項背的優點：首先：MRAM不需充放電保持記錄，所以他是非揮發性低耗能的紀錄元件，再者，磁性材料不像DRAM是由半導體製成，所以MRAM具有抗輻射的功能。同時MRAM的製作可以配合現已成熟的半導體製程。
但是，MRAM的製程良率一直有待克服，很重要的原因就是在應用時，小磁區結構的翻轉過程，和其尺寸，厚薄，材料，幾何形狀，缺陷，……等等都還有待研究以釐清這些影響間的交互作用。
藉著微影技術的成熟，本實驗得以設計實驗來瞭解上述小磁區結構翻轉過程中的現象。我們利用系統化的排列八邊形磁性鎳鐵薄膜成不同幾何排列的長鍊，來研究其翻轉過程中異向性與磁疇結構間的效應。希望這些工作能對將來磁性的應用有所貢獻。在本論文中，我們透過PPMS（Physical Property Measurement System）來量測磁阻，並利用MFM（Magnetic Force Microscopy）來觀察磁疇的狀態，並藉由兩種分析結果間的比對，解釋翻轉過程中的現象與我們排列長鍊八邊形鎳鐵樣品幾何形狀間的效應。這些效應略述如下：一、藉由分隔開八邊形磁單元，使鐵鎳線形成個別的磁單疇。二、加入垂直於長鍊的八邊形磁單元，可以在少量影響AMR效應下，幫助磁區結構翻轉。三、加入的這些垂直長鍊磁單元內部磁區是兩個vortex態的磁單元。四、透過臨場MFM（磁性探針顯微鏡），直接觀察到對應於磁阻改變的磁區結構轉變過程。

Advances in lithography and pattern transfer techniques have provided the opportunity of exploring novel magnetic phenomena in controlled shapes. In particular, the magnetic thin films have been extensively investigated because of their importance in both magnetoresistance (MR) devices and more recently, magneto electronic devices. An understanding of the magnetization reversal processes and magnetoresistance (MR) response in small ferromagnetic elements is also important for the design and optimization of miniature MR heads for ultrahigh density data storage applications. There have been numerous efforts to investigate the magnetization reversal and MR behavior in Permalloy (Ni80Fe20) wires so far. Recent studies have demonstrated that the strong dependence of switching field and magnetization reversal the shape is attributed to the formation of domains, even in submicron structures, which are crucial in the magnetization reversal process.
The shape of a wire structure has a decisive influence on magnetic properties in the micron size range. For example, the MR behaviors are found to change significantly in submicron-sized Ni80Fe20 modulated octagon in arrangement of chain.
In this thesis, we have presented an arrangement in octagon Permalloy in chain, leading to a striking variation in the magnetoresistance. We’ve demonstrated that it’s possible to control the switching field by introducing the different number of rectangular Permalloy octagons in chain and facilitating magnetoresistance behavior during magnetic reversal. Our results suggested to “introducing” domain walls in patterned magnetic wire, and which can be used for studies of domain wall effect. We discussed the geometrical effect of the arrangement of the octagon chains on the switching field associated with domain configurations inferred from the magnetic force microscopy (MFM) imaging and physical property measurement system (PPMS).
After systematic experiments, we can propose that the different arrangement of octagons provides a way to control the switching field and MR Ratio of submicron permalloy wire. Of course, having suggestion that thickness and aspect ratio also have influences on the patterned permalloy wire itself during magnetization process. Based on our observation on magnetic force microscopy images, we would claim that we understand the domain characteristic during magnetization process. At remanent state, by our design of inducing magnetic unit in a wire, there will be vortex state domain take shape in the unit vertical to the chain; the domains in the units which connect to each other parallel to the chain will form a single domain aligned in the same direction. Real time magnetic force microcopy images give evidence for the results of the experiments showing that under transverse applied field that spin rotates in the unit parallel to the chain; domain change forms from vortex at remanent state to single domain aligned to the applied field. Under longitude applied field, in the unit vertical to the chain, domain change forms from vortex at remanent state to single domain vertical to the major axis aligned to the applied field. We also find that although the octagon arrangements influence the switching field, the AMR of each pattern is similar.

致謝
Acknowledgements
中文摘要
Abstract
Table of Contents
List of Tables
List of Figures
CHAPTER 1 INTRODUCTION
1.0 Background
1.1 Electrical and Magnetic Properties of Thin Film
1.2 Literature Review of Magnetoresistance
1.3 Property of Permalloy
1.4 The Magnetoresistance Research of Various Patterns
1.5 Review of MFM Research on Magnetic Elements
CHAPTER 2 EXPERIMENTAL TECHNIQUES
2.1 The Pattern Design
2.2 Lithography and Film Growth
2.3 Magnetoresistance Measurement
2.4 Magnetoresistance Calculation
2.5 Measurement of Magnetic Force Microscopy
CHAPTER 3 RESULTS (I) : Magnetoresistance
3.1 Straight Wire versus Octagon Units in Chain
3.2 Patterned Octagon Wires with Thickness of 20nm and 40nm
3.3 Patterned Octagon Wire with Aspect Ratio 3.3 and 5
3.4 Introducing Different Density of Octagon Units Vertical to the Chain
CHAPTER 4 RESULTS (II) : MFM IMAGES
4.1 Scanning MFM Images at Remanent State
4.2 Real Time MFM Images
CHAPTER 5 DISCUSSIONS
CHAPTER 6 CONCLUSION
References
Appendix
1.Property of Permalloy Bulk
2.Homemade Magnetoresistance Measurement System
3.MFM settings
Publication
1.International Journal of Nanoscience (IJN) : Abstract(Asia SPM4 & Taipei Symposium on Nanotechnology)
2.第十五屆磁學與磁性技術協研討會 : proceeding
3.2002奈米科技學術研討會：海報
4.2002物理雙月刊2月號 : 海報

R. P. Cowburn, J. Phys. D: Appl. Phys. 33, R1-R16 (2000)
Moore G E, Int. Electronic Devices Meeting (IEDM) (Technical Digest), 75, p11 (1975)Prinz G A, Science, 282, 1660 (1998)Baibich M N, Broto J M, Fert A van Dau F N, Petroff F, Etienne P, Creuzet G, Friederich A and Chazelas, J. Phys. Rev. Lett. , 61, 2472 (1988)Jonker B T, Walker K-H, Kisker E, Prinz G A and Carbone C, Phys. Rev. Lett. ,57, 142 (1986)Robert C O’handley , Modern Magnetic Materials – Principles and ApplicationsMilton Ohring, The Materials Science of Thin FIlmsB D Cullity, Introduction to Magnetic MaterialsKimin Hong, N. Giordano, Phys. Rev. B 51 9855 (1995)J. I. Martý´n, J. Nogue´ s et al, Appl. Phys. Lett., 72 ,No. 2, 257 (1998)S.Pignard, G.Goglio et al, J. Appl. Phys. ,87 No. 2, 824 (2000)A.O.Adeyeye, J.A.C.Bland et al, J. Appl. Phys. , 79, 6120 (1996)R. D. Gomez, T. V. Luu, A. O. Pak, I. D. Mayergoys, K. J. Kirk and J. N. Chapman, J. Appl. Phys. , 85, 4598, (1999)J C Wu, Y W Huang , H W Huang, T H Wu, Jpn. J. Appl. Phys. 38, 6711 (1999)J. C. Wu and H. W. Huang, J. Appl. Phys. 87, No. 91, 4948 (2000)Chang Sze, ULSI TechnologyYong Qiang Jia and Stephen Y. Chou, J. Appl. Phys., 81, 5461 (1997)Y. Jaccard, Ph. Guittionne et al, Phys. Rev. B, 62, 1141 (2000)Jian-Gang Zhu and Yooufeng Zheng, J. Appl. Phys.( Symposium on Magnetic Technology for a single Chip Computer), 87, 6668 (2000)W.Y. Lee, C.C.Yao et al, J. Appl. Phys., 87, 3032 (2000)
J. Bass, in Metals, Electronics Transport Phenomena, Landolt-Bornstein, New Series, Group 3, Vol. 15a, edited by K. H. Hell-wege and J. L. Olsen Berlin, (1982).
E. C. Stoner and E. P. Wohlfarth, Philos. Trans. R. Soc. London, Ser. A 240, 599 (1948) reprinted in IEEE Trans. Magn. 27, 3475 (1991)
A. Aharoni, Introduction to the Theory of Ferromagnetism, Oxford, (1996)
J. Jorritsma and J. A. Mydosh, J. Appl. Phys. 84, 901 (1998)
S. Pignard, G. Goglio, A. Radulescu, L. Piraux, S. Duboix, A. Decle´my, and J. L. Duvail, J. Appl. Phys. 87, 824 (2000).
J. I. Martin, J. Nogue´s, I. K. Schuller, M. J. Van Bael, K. Temst, C. Van Haesendonck, V. V. Moshchalkov, and Y. Bruynser-aede, Appl. Phys. Lett. 72, 255 (1998).
U. Ebels, Phys. Rev. Lett., 84, 983(2000)
H. Jaffre ` s, L. Ressier, J. P. Peyrade, and A. R. Fert, J. Appl. Phys. 84, 4375(1998)
R. D. Gomez, T. V. Luu, and A. O. Pak J. Appl. Phys. 85, 6163(1999)
北京中科院韓寶善教授中研院演講（2002三月）
鄭德娟教授中研院演講（2002六月）
A.Kihc, J. Magnetism and Magnetic Materials, 146, 298(1995)
E. Girgis, J. Schelten, Appl. Phys. Lett., 76 No.25, 3780(2000)
A. Kiriyuk, J. Magnetism and Magnetic Materials, 171, 45(1997)
I.Bergenti,A.Deriu,F.Licci,G.Turilli,G.Cicognani, Phys. B 301 105(2001)
T. Ono, H. Miyajima, J. Appl. Phys., 85, 6181(1999)
T. Taniyama, J. Appl. Phys., 76, 6181(2000)
Y. B. Xu, C. A. F. Vaz, A. Hirohata, H. T. Leung, C. C. Yao, and J. A. C. Bland, Phys. Rev. B, 61 R14, 901(2000)
J. Rothman, M. Kläui, L. Lopez-Diaz, C. A. F. Vaz, A. Bleloch, J. A. C. Bland, Z. Cui, and R. Speaks, Phys. Rev. Lett., 86, 1098(2001)
J. Ferre, J. Magnetism and Magnetic Materials, 171, 45(1997)
M. Kla¨ ui, J. Rothman, L. Lopez-Diaz, C. A. F. Vaz, and J. A. C. Bland, Appl. Phys. Lett., 78 No.21, 3268(2001)
Jing Shi, Appl. Phys. Lett., 77 No.11, 1692(2000)
M. Lederman, Phys. Rev. Lett., 73, 1986(1994)
F. J. Jedema, A. T. Filip & B. J. van Wees, Nature, 410, 345(2001)
R. P. Cowburn, M. E. Welland, Science, 287, 1466(2000)
J. O’Donnell and J. N. Eckstein, Appl. Phys. Lett. 76 No.2, 218(2000)