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This dissertation, "Macrospin and Micromagnetic Simulations of Spintronic Devices for Magnetic Sensors and Oscillator Applications" by Tui, Zeng, 曾推, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: In this thesis, by categorizing the application of spintronic devices with the standard of signal type being processed, the spintronic devices based magnetic field sensors which process the D.C. signal are studied with micromagnetic simulation and the spintronic devices based spin-torque oscillators which process the A.C. signal are studied with macrospin simulation. By conducting micromagnetic simulation, the thermally excited mag-noise in spintronic device based magnetic field sensors is systematically studied. In magnetic tunnel junctions (MTJ) based magnetic field sensor, the spatial distribution of the thermally excited mag-noise indicates that the edges are the main contributor of thermal mag-noise in the free layer (FL). Both hard bias (HB) field and applied field could suppress the thermal mag-noise in edges. A relatively high applied field will decrease the influence of HB field on mag-noise in edges. The edge effect is not applicable for MTJ sensors with circular cross section. In ferromagnetic ring structure based magnetic field sensor, the saturated state, triangle state, half triangle state, onion state, and vortex state are explored and studied, respectively. The mag-noise calculation shows that triangle state is the main reason for the mag-noise exhibiting 1/f tendency in both the low-frequency range and high-frequency range in relaxed state, while the onion state explains why a noise peak appears in high-frequency range in the relaxed state. It is proved that the area of the ferromagnetic rings is not the determining factor for the thermal mag-noise distribution in the saturated state. In dual-vortex structure based magnetic field sensor, the combination of the dual-vortex motion and the magnetic noise properties make it possible to measure the external field (along hard bias direction) through measuring the FMR peak positions or the integrated thermal mag-noise, which indicated two novel field sensing mechanisms using elliptical permalloy single layer. Besides the study of the thermally excited mag-noise in spintronic device based magnetic field sensors, the spintronic device based spintorque oscillators (STOs) is fully investigated by macrospin simulation. Conclusions demonstrate numerically and analytically how a STO locks to a microwave field (Hac). A magnetic energy based analysis is used to explain this phenomenon. This result provides a possible way to synchronize serially connected STOs by tuning each single STO's phase shift with external microwave field, which could finally enhance the locking efficiency, locking range and output power of serially connected STOs. Meanwhile, the capacitance effect on the oscillation characteristics and the switching characteristics of the STOs has also been studied. The micromagnetic simulation of the noise sources in traditional GMR/TMR based magnetic field sensor and novel spintronic device based magnetic field sensors not onlyprovide reliable explanations of noise-related phenomenon in magnetic field sensors but also offer guidance on how to fabricate magnetic field sensors with relative low thermal magnetic noise and high performance. Meanwhile, the macrospin study of the spin-torque oscillators which process A.C electrical current signal has provided theoretical fundamentals for next generation microwave generator. Subjects: Spintronics - Materials Magnetic materials
The history of scientific research and technological development is replete with examples of breakthroughs that have advanced the frontiers of knowledge, but seldom does it record events that constitute paradigm shifts in broad areas of intellectual pursuit. One notable exception, however, is that of spin electronics (also called spintronics, magnetoelectronics or magnetronics), wherein information is carried by electron spin in addition to, or in place of, electron charge. It is now well established in scientific and engineering communities that Moore's Law, having been an excellent predictor of integrated circuit density and computer performance since the 1970s, now faces great challenges as the scale of electronic devices has been reduced to the level where quantum effects become significant factors in device operation. Electron spin is one such effect that offers the opportunity to continue the gains predicted by Moore's Law, by taking advantage of the confluence of magnetics and semiconductor electronics in the newly emerging discipline of spin electronics. From a fundamental viewpoine, spin-polarization transport in a material occurs when there is an imbalance of spin populations at the Fermi energy. In ferromagnetic metals this imbalance results from a shift in the energy states available to spin-up and spin-down electrons. In practical applications, a ferromagnetic metal may be used as a source of spin-polarized electronics to be injected into a semiconductor, a superconductor or a normal metal, or to tunnel through an insulating barrier.
This book constitutes the proceedings of the 18th International Conference on Unconventional Computation and Natural Computation, UCNC 2019, held in Tokyo, Japan, in June 2019. The 19 full papers presented were carefully reviewed and selected from 32 submissions. The papers cover topics such as hypercomputation; chaos and dynamical systems based computing; granular, fuzzy and rough computing; mechanical computing; cellular, evolutionary, molecular, neural, and quantum computing; membrane computing; amorphous computing, swarm intelligence; artificial immune systems; physics of computation; chemical computation; evolving hardware; the computational nature of self-assembly, developmental processes, bacterial communication, and brain processes.
The present book is the second edition of Amikam Aharoni's Introduction to the Theory of Ferromagnetism, based on a popular lecture course. Like its predecessor, it serves a two-fold purpose: First, it is a textbook for first-year graduate and advanced undergraduate students in both physics and engineering. Second, it explains the basic theoretical principles on which the work is based for practising engineers and experimental physicists who work in the field of magnetism, thus also serving to a certain extent as a reference book. For both professionals and students the emphasis is on introducing the foundations of the different subfields, highlighting the direction and tendency of the most recent research. For this new edition, the author has thoroughly updated the material especially of chapters 9 ('The Nucleation Problem') and 11 ('Numerical Micromagnetics'), which now contain the state of the art required by students and professionals who work on advanced topics of ferromagnetism. From reviews on the 1/e: '... a much needed, thorough introduction and guide to the literature. It is full of wisdom and commentary. Even more, it is Amikam Aharoni at his best - telling a story... He is fun to read... The extensive references provide an advanced review of micromagnetics and supply sources for suitable exercises... there is much for the student to do with the guidance provided by Introduction to the Theory of Ferromagnetism.' A. Arrott, Physics Today, September 1997
Advances in the synthesis of new materials with often complex, nano-scaled structures require increasingly sophisticated experimental techniques that can probe the electronic states, the atomic magnetic moments and the magnetic microstructures responsible for the properties of these materials. At the same time, progress in synchrotron radiation techniques has ensured that these light sources remain a key tool of investigation, e.g. synchrotron radiation sources of the third generation are able to support magnetic imaging on a sub-micrometer scale. With the Fifth Mittelwihr School on Magnetism and Synchrotron Radiation the tradition of teaching the state-of-the-art on modern research developments continues and is expressed through the present set of extensive lectures provided in this volume. While primarily aimed at postgraduate students and newcomers to the field, this volume will also benefit researchers and lecturers actively working in the field.
Hybrid organic-inorganic perovskites (HOIPs) have attracted substantial interest due to their chemical variability, structural diversity and favorable physical properties the past decade. This materials class encompasses other important families such as formates, azides, dicyanamides, cyanides and dicyanometallates. The book summarizes the chemical variability and structural diversity of all known hybrid organic-inorganic perovskites subclasses including halides, azides, formates, dicyanamides, cyanides and dicyanometallates. It also presents a comprehensive account of their intriguing physical properties, including photovoltaic, optoelectronic, dielectric, magnetic, ferroelectric, ferroelastic and multiferroic properties. Moreover, the current challenges and future opportunities in this exciting field are also been discussed. This timely book shows the readers a complete landscape of hybrid organic-inorganic pervoskites and associated multifuctionalities.
Written by two well-known researchers in the field, this useful reference takes an applied approach to high frequency processes including oscillations and waves in ferromagnets, antiferromagnets, and ferrimagnets. Problems evaluated include ferromagnetic and antiferromagnetic resonances, spin waves, nonlinear processes, and high frequency manifestations of interactions between the magnetic system and other systems of magnetically ordered substances as elastic waves and charge carriers. Unlike previous monographs on this subject, which are highly theoretical and written for very advanced readers, this book requires only an average college background in mathematics and experimental physics. It will be a valuable addition to the library of engineers and scientists in research and development for communications applications, and scientists interested in nonlinear magnetic phenomena. It also serves as an excellent introduction to the topic for newcomers in the field. Magnetization Oscillations and Waves not only presents results but also shows readers how to obtain them; most formulas are derived with so many details that readers can reproduce them. The book includes many summaries and tables and detailed references to significant work in the area by European researchers.
This book provides a comprehensive introduction to spintronics-based computing for the next generation of ultra-low power/highly reliable logic. It will cover aspects from device to system-level, including magnetic memory cells, device modeling, hybrid circuit structure, design methodology, CAD tools, and technological integration methods. This book is accessible to a variety of readers and little or no background in magnetism and spin electronics are required to understand its content. The multidisciplinary team of expert authors from circuits, devices, computer architecture, CAD and system design reveal to readers the potential of spintronics nanodevices to reduce power consumption, improve reliability and enable new functionality.