Spin Wave Theory And Its Applications To Neutron Scattering And Thz Spectroscopy

Two of the most powerful tools used to study magnetic materials are inelastic neutron scattering and THz spectroscopy. Because the measured spectra provide a dynamical fingerprint of a magnetic material, those tools enable scientists to unravel the structure of complex magnetic states and to determine the microcscopic interactions that produce them. This book discusses the experimental techniques of inleastic neutron scattering and THz spectroscopy and provides the theoretical tools required to analyze their measurements using spin-wave theory. For most materials, this analysis can resolve the microscopic magnetic interactions such as exchange, anisotropy, and Dzyaloshinskii-Moriya interactions. Assuming a background in elementary statistical mechanics and a familiarity with the quantized harmonic oscillator, this book presents a comprehensive review of spin-wave theory and its applications to both inelastic neutron scattering and THz spectroscopy. Spin-wave theory is used to study several model magnetic systems, including non-collinear magnets such as spirals and cycloids that are produced by geometric frustration, competing exchange interactions, or Dzyaloshinskii-Moriya interactions. Several case studies utilizing spin-wave theory to analyze inelastic neutron-scattering and THz spectroscopy measurements are presented. These include both single crystals and powders and both oxides and molecule-based magnets. In addition to sketching the numerical techniques used to fit dynamical spectra based on microscopic models, this book also contains over 70 exercises that can be performed by beginning graduate students.

Modern Problems in Condensed Matter Sciences, Volume 22.1: Spin Waves and Magnetic Excitations, Part I focuses on the principles, methodologies, approaches, and reactions involved in spin waves and magnetic excitations, including, Brillouin-Mandelstam light scattering, optical magnetic excitations, and magnetic dielectrics. The selection first elaborates on spin waves in magnetic dielectrics current status of the theory and light scattering from spin waves. Discussions focus on magneto-optic effects and the mechanism of light scattering in magnets, Brillouin-Mandelstam light scattering, Raman scattering, Collinear Heisenberg ferromagnet, low-temperature phase transitions, and low-dimensional systems. The text then ponders on optical magnetic excitations, spin waves above the threshold of parametric excitations, and theory of spin excitations in rare earth systems. Topics include Hamiltonian for rare earth systems, parametric instability of spin waves in magnetic dielectrics, nonstationary processes in parametric excitation of spin waves, radiative decay of magnetic excitons, and mechanism of the generation of magnetic excitations by light. The book tackles 4f moments and their interaction with conduction electrons and neutron scattering studies of magnetic excitations in itinerant magnets, including magnetic excitations at finite and low temperatures, paramagnetic scattering, coupling to conduction electrons, and virtual magnetic excitations. The selection is highly recommended for researchers wanting to study spin waves and magnetic excitations.

Neutron spin echo (NSE) spectroscopy is the highest energy resolution neutron scattering technique available for examining a large area (in time and space) in condensed matter physics. This broad dynamic and spatial range is extensively exploited in the study of a wide range of scientific problems ranging from the dynamics of glasses, polymer melts, complex fluids and microemulsions to the elementary excitations in superfluid 4He and to ferromagnets and spin glasses. This book reviews the current status and future prospects in NSE spectroscopy describing the method, latest instrumentation and also the use of NSE in fundamental, hard- and soft-matter science. It provides first-hand information for researchers working in the fields touched by NSE. In addition, young researchers, PhD students and graduates interested in the method will obtain a comprehensive overview and guidelines to implementing the NSE technique.

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.

The second edition of this book on nanomagnetism presents the basics and latest studies of low-dimensional magnetic nano-objects. It highlights the intriguing properties of nanomagnetic objects, such as thin films, nanoparticles, nanowires, nanotubes, nanodisks and nanorings as well as novel phenomena like spin currents. It also describes how nanomagnetism was an important factor in the rapid evolution of high-density magnetic recording and is developing into a decisive element of spintronics. Further, it presents a number of biomedical applications. With exercises and solutions, it serves as a graduate textbook.

Since the earliest days of human existence, the clash of thunder and trembling of the hills has struck fear into the hearts of seasoned warriors and tribal villagers alike. Great gods, demi-gods, and heroes were created to explain the awesome, mysterious, and incomprehensibly powerful forces of Nature in a feeble attempt to make sense of the world around them. To our advanced scientific minds today, these explanations seem childish and ridiculous; however, the power to flatten thousands of square miles of ancient forest, create massive holes in the Earth itself, and cause mountains to tremble to their very roots are more than enough reason to believe. Indeed, perhaps our scientific advancement has caused us to not fully or completely appreciate the awesome scale and power that Nature can wield against us. The study of shock wave formation and dynamics begins with a study of waves themselves. Simple harmonic motion is used to analyze the physical mechanisms of wave generation and propagation, and the principle of superposition is used to mathematically generate constructive and destructive interference. Further development leads to the shock singularity where a single wave of immense magnitude propagates and decays through various media. Correlations with the fields of thermodynamics, meteorology, crater formation, and acoustics are made, as well as a few special applications. Direct correlation is made to events in Arizona, Siberia, and others. The mathematical requirement for this text includes trigonometry, differential equations, and large series summations, which should be accessible to most beginning and advanced university students. This text should serve well as supplementary material in a course covering discrete wave dynamics, applied thermodynamics, or extreme acoustics.

Inelastic neutron scattering has been used to measure spin wave excitations in the quasi-one dimensional S = 3/2 magnetic material CsVBr3. Dispersion relations were determined using standard triple-axis methods. Fits to linear spin wave theory yield model Hamiltonian parameters describing magnetic interactions in the system.

Neutron Scattering from Magnetic Materials is a comprehensive account of the present state of the art in the use of the neutron scattering for the study of magnetic materials. The chapters have been written by well-known researchers who are at the forefront of this field and have contributed directly to the development of the techniques described. Neutron scattering probes magnetic phenomena directly. The generalized magnetic susceptibility, which can be expressed as a function of wave vector and energy, contains all the information there is to know about the statics and dynamics of a magnetic system and this quantity is directly related to the neutron scattering cross section. Polarized neutron scattering techniques raise the sophistication of measurements to even greater levels and gives additional information in many cases. The present book is largely devoted to the application of polarized neutron scattering to the study of magnetic materials. It will be of particular interest to graduate students and researchers who plan to investigate magnetic materials using neutron scattering. · Written by a group of scientist who have contributed directly in developing the techniques described.· A complete treatment of the polarized neutron scattering not available in literature.· Gives practical hits to solve magnetic structure and determine exchange interactions in magnetic solids.· Application of neutron scattering to the study of the novel electronic materials.