Spin Waves

This book begins by introducing magnetism and discusses magnetic properties of materials, magnetic moments of atoms and ions, and the elements important to magnetism. It covers magnetic susceptibilities and electromagnetic waves in anisotropic dispersive media among other topics. There are problems at the end of each chapter, many of which serve to expand or explain the material in the text. The bibliographies for each chapter give an entry to the research literature.

In the past few years, there has been a rapidly growing interest in the properties of spin waves (or magnons) in ordered magnetic materials. These are the low-lying excitations that characterize the dynamical behavior of the magnetization variables in ferromagnets, ferrimagnets and antiferromagnets, particularly at low temperatures. Many of the recent developments concerning spin waves have been directed towards understanding their behavior in limited magnetic samples. At the same time, there have been dramatic advances in the experimental techniques, both for preparing high-quality magnetic samples in the form of thin films and superlattices and for the study of the spin-wave excitations themselves. Magnetic thin films have long been of technological as well as scientific interest and an understanding of both the linear and nonlinear aspects of their magnetic behavior is important.

Modern Problems in Condensed Matter Sciences, Volume 22.2: Spin Waves and Magnetic Excitations focuses on the processes, methodologies, reactions, principles, and approaches involved in spin waves and magnetic excitations, including magnetic systems, fluctuations, resonance, and spin dynamics. The selection first elaborates on spin-wave resonance in metals, excitations in low-dimensional magnetic systems, and the theory of magnetic excitations in disordered systems. Topics include spin waves in ferromagnets with weak fluctuations of the exchange interaction; dynamics of propagating excitations; models of two-dimensional magnetic systems; spin-wave resonance in bulk metals; and standing spin-wave resonance in thin films. The manuscript then ponders on spin dynamics of amorphous magnets and magnetic excitations in spin glasses, including dynamics in reentrant spin glasses, dynamics of classical spin glasses, spin dynamical theory, spin dynamics of locally isotropic materials, and effects of dilution. The book takes a look at nuclear spin and magnetoelastic excitations and magnetic impuritons in antiferromagnetic dielectric crystals. Discussions focus on coherent and incoherent impurity excitations, equations of motion and the energy of a magnetoelastic medium, magnetoelastic excitations near magnetic orientational phase transitions, and the effect of frequency pulling on the behavior of nuclear spin echo signals. The selection is a vital source of data for researchers interested in spin waves and magnetic excitations.

Understanding, controlling and, more importantly, enhancing the interaction between light (photons) and spin waves (magnons) can be, among others, a step towards the realization of magnon-mediated microwave-to-optical transducers for quantum computing applications or hybrid solid-state spintronic-photonic interconnections. In this respect, the development of novel composite multifunctional micro/nanostructures — so-called optomagnonic — which simultaneously control optical and spin waves and enhance their interaction, is particularly attractive.This book constitutes a collective work, comprising seven chapters from leading researchers in the field of optomagnonics and related areas. Apart from exciting recent developments, it provides the necessary fundamental knowledge in an explanatory manner and, therefore, it is accessible to non-experts. It is suitable for PhD students, post-docs, and researchers who are willing to get engaged in optomagnonics, while selected parts could also serve as lecture material for advanced courses. With increasing demand for miniaturized optomagnonic devices, this book will be an important resource to researchers working on optomagnonics, magneto-optics, spintronics, as well as on hybrid micro/nano devices for information processing.

The aim of this advanced textbook is to provide the reader with a comprehensive explanation of the ground state configurations, the spin wave excitations and the equilibrium properties of spin lattices described by the Ising–Heisenberg Hamiltonians in the presence of short (exchange) and long range (dipole) interactions. The arguments are presented in such detail so as to enable advanced undergraduate and graduate students to cross the threshold of active research in magnetism by using both analytic calculations and Monte Carlo simulations. Recent results about unorthodox spin configurations such as stripes and checkerboards should then excite theoreticians in the field of magnetism and magnetic materials research. Contents:Magnetic HamiltoniansSpin Waves in FerromagnetsInteracting Spin Waves in FerromagnetsFeynman Diagrams Expansion in FerromagnetsTwo-Magnon Bound States in FerromagnetsPerturbation Theory in Planar FerromagnetsSpin Waves in Non-Collinear SystemsSpin Waves in MultilayersSpin Waves in Systems with Long Range InteractionLong Range Interactions in 2D Systems Readership: Students and professionals interested in the fields of theoretical magnetism and magnetic material research. Keywords:Spin Waves;Many-Body Theory in Magnetism;Two-Magnon Bound States;Helix Spin Configurations;Stripe and Checkerboard Spin ConfigurationsKey Features:Many-body theory applied to magnetic insulators: the Green function approach is compared to the Feynman diagram expansionTwo spin wave deviations from clusters to thermodynamic limitStripe and checkerboard configurationsReviews: “The book combining the modern problems of statistical mechanics, directed to the study of magnetic excitations in different systems, with strict mathematical statement and the solution of the corresponding problems will be very useful for undergraduate and graduate students studying the magnetism problems, and also for theoreticians researching magnetism and magnetic materials.” Zentralblatt MATH

This is a book of informal research papers written by George J Bugh while investigating claims by many inventors and researchers who have built unusual electromagnetic devices said to produce anomalous energy output and even electrogravity effects.Mr. Bugh is a senior staff aerospace electronics engineer with over 20 years experience. He spent the last 7 years studying these claims to determine if any could be valid and if so then to determine the source of the anomalous energy and the electrogravity effects.According to classical electrodynamics, all electrically charged particles, like quarks and electrons, should radiate away energy from gyroscopic precessional motions and orbital motions. Bugh has come to the conclusion that they really do. However, all particles are also absorbing just as much energy from all other radiating particles.The continuously absorbed energy equals the radiated energy and applies forces that move similar type particles into harmonious precesssional motions with each other. This results in a sea of electromagnetic standing waves among all matter in the universe.It is this sea of standing waves rather than quantum probability waves that best account for the wave like nature of matter. Particles move to quantized states because of electromagnetic forces that keep particle motions synchronized with this sea of standing waves.This is an interaction among all matter that Ernst Mach alluded to as necessary to cause matter's characteristic of inertia. Einstein called this Mach's Principle. Einstein studied Mach's ideas while developing his theory of General Relativity.Using common sense and classical electrodynamics, Bugh explains how these particle spin interactions are possible even among compensating spins. Technology advancements are possible based on these particle spin interactions.

Since the publication of the first edition of Spin-Wave Confinement, the magnetic community’s interest in dynamic excitations in magnetic systems of reduced dimensions has been increasing. Although the concept of spin waves and their quanta (magnons) as propagating excitation of magnetic media was introduced more than 80 years ago, this field has been repeatedly bringing us fascinating new physical phenomena. The successful development of magnonics as an emerging subfield of spintronics, which considers confined spin waves as a basis for smaller, faster, more robust, and more power-efficient electronic devices, inevitably demands reduction in the sizes and dimensions of the magnetic systems being studied. The unique features of magnons, including the possibility of carrying spin information over relatively long distances, the possibility of achieving submicrometer wavelength at microwave frequencies, and controllability by electronic signal via magnetic fields, make magnonic devices distinctively suited for implementation of novel integrated electronic schemes characterized by high speed, low power consumption, and extended functionalities. Edited by S. O. Demokritov, a prominent magnonics researcher who has successfully collected the results of cutting-edge research by almost all main players in the field, this book is for everyone involved in nanotechnology, spintronics, magnonics, and nanomagnetism.