From Bulk to Nano (eBook)

Dr. Stefanita is a physicist/materials scientist who received her Ph. D. degree in Physics (Magnetic Nondestructive Testing and Materials Characterization) from Queen’s University, Kingston, Ontario, Canada in 1999. Her Ph.D. thesis is entitled "Surface Magnetic Barkhausen Noise Response To Plastic Yield of Steel". Previously, she received her Diploma of Engineer in Physics (Technological Physics) from the University of Bucharest, Romania in 1989 with the thesis entitled "Apparatus for Measuring Solar Radiation Using a Thin Film Transducer". Dr. Stefanita also has a 1984 Baccalaureate in Mathematics and Physics from the German School of Bucharest in Romania. Dr. Stefanita has over 15 years collective experience in academia and industry with international exposure on 3 continents, and 5 countries. Her most recent research experience is in nanotechnology, in self-assembled metallic and semiconductor nanowires or nanodots, spintronics, magnetotransport, Hall effect, and infrared absorption and transmission, acquired during her work at Virginia Commonwealth University in Richmond, Virginia, USA. Her previous work in magnetism in the 1990s at Queen’s University involves magnetic behavior of plastically deformed steel, microyielding phenomena, cold rolling effects on magnetic properties; magnetic nondestructive testing techniques for detecting defects in steel components. She has also developed a prototype for a medical diagnostics apparatus based on a thin film interference filter, at the University of Alberta in Edmonton, Alberta, Canada. Dr. Stefanita’s previous work as a materials scientist in South Africa, and in Germany and Romania is in the areas of failure analysis, scanning electron microscopy, energy dispersive X- ray analysis, atomic emission spectroscopy and import of chemicals and raw materials. Dr. Stefanita is a co-founder and Senior Partner with NanoDotTek based in the Boston area, Massachusetts, USA. This company is dedicated to promoting nanotechnology, and allied areas such as non-destructive testing (the "NDT" in NanoDotTek) for engineering systems. With respect to the latter Dr. Stefanita is presently engaged in developing a lossy dielectric with a prescribed fractional impedance. This is in furtherance of improving fractional order control systems and pulse shaping for wireless broadband communications. This work is in collaboration with engineers in California and Mexico. Dr. Stefanita also has experience in teaching. Her lectures have covered solid state devices, electromagnetics, and mechanics of deformables. Dr. Stefanita is a regular referee for nanotechnology papers, as well as a published author of journal papers, conference publications, and internal reports. The latter reports are in many cases in relation to contract-based research. Dr. Stefanita’s most recent journal paper in spintronics appeared in Nature Nanotechnology earlier this year. Finally, note that Dr. Stefanita is a licensed Professional Engineer in the Province of Alberta, Canada.

Preface 7
Contents 10
Symbols 15
Greeks 17
1 Introduction 19
1.1 Review of Certain Historic Magnetic Concepts 20
1.2 Origins of Magnetism on an Atomic Scale 24
1.3 Structure-Dependent Micromagnetism 29
1.4 Towards Technological Advancements 33
References 34
2 Barkhausen Noise as a Magnetic Nondestructive Testing Technique 36
2.1 Introduction 36
2.2 A Basic Definition of Magnetic Barkhausen Noise 37
2.3 Stress Effects 41
2.4 Effects of Microstructure on MBN 50
2.5 Competitiveness of MBN in Nondestructive Evaluation 53
References 55
3 Combined Phenomena in Novel Materials 58
3.1 The Interest in Magneto-optical Media 58
3.2 Magnetoelectric Materials 68
References 81
4 Magnetoresistance and Spin Valves 88
4.1 Introduction 88
4.2 A Simple Way of Quantifying Magnetoresistance 89
4.3 What is Responsible for GMR? 89
4.4 Deskstar 16 GP 90
4.5 Spin-down” vs. Spin-up” Scattering: Magnetic Impurities 90
4.6 Fabrication of GMR Multilayers: Thin Films and Nanostructures 91
4.7 Spin Valves 92
4.8 The Role of Exchange Bias 92
4.9 Ni–Fe Alloys 93
4.10 Ternary Alloys 94
4.11 Ni–Fe Alloys with Higher Fe Content 94
4.12 Basic Principles of Storing Information Magnetically 95
4.13 Materials for spin valve Sensors 97
4.14 The Need for Proper Sensor Design 98
4.15 Magnetic Tunnel Junctions 99
4.16 Anisotropic Magnetoresistive Sensors 99
4.17 Extraordinary Magnetoresistance 100
4.18 GMR Sensors with CPP Geometry 100
4.19 Dual Spin Valves 101
4.20 Some GMR Multilayer Material Combinations 102
4.21 Ferromagnetic/Nonmagnetic Interfaces 103
4.22 The Nonmagnetic Spacer 103
4.23 Magnetic Tunneling 104
4.24 The Magnetic Tunnel Transistor 104
4.25 Some Special Types of Ferromagnets 105
4.26 Colossal Magnetoresistance 106
4.27 CPP Geometry Preferred in Sensors 107
4.28 Spin Valves in Commercial Applications 108
References 110
5 Some Basic Spintronics Concepts 116
5.1 Encoding Information: Emergence of Spintronics 116
5.2 Spin Injection 117
5.3 Control of Spin Transport 128
5.4 Spin Selective Detection 136
References 138
6 Trends in Magnetic Recording Media 145
6.1 The Popularity of Magnetic Tapes 145
6.2 Bit Patterned Magnetic Media 150
6.3 Self-assembly and Magnetic Media 155
6.4 Present Alternatives for Discrete Media Production 161
References 169
7 Concluding Remarks 177
Reference 177
Index 178