Magnon

About: Magnon is a research topic. Over the lifetime, 7072 publications have been published within this topic receiving 123150 citations.

Magnetization Oscillations and Waves

Abstract: Isotropic Ferromagnet Magnetized to Saturation Ferromagnetism Elementary Magnetic Moments Paramagnetism Weiss Theory Exchange Interaction Equation of Motion of Magnetization High-Frequency Magnetic Susceptibility Solution of the Linearized Equation of Motion Peculiarities of the Susceptibility Tensor High-Frequency Permeability Allowance for Magnetic Losses Dissipative Terms and Dissipation Parameters Susceptibility Tensor Components Uniform Oscillations in a Small Ellipsoid Internal and External Magnetic Fields Eigenoscillations Forced Oscillations Anisotropic Ferromagnet Landau-Lifshitz Equation Generalization of Equation of Motion Methods of Analysis of Ferromagnetic Resonance in Anisotropic Ferromagnet Magnetocrystalline Anisotropy Origins of Magnetocrystalline Anisotropy Phenomenological Description Equilibrium Orientations of Magnetization Ferromagnetic Resonance in a Single Crystal Sphere of Uniaxial Ferromagnet Sphere of a Cubic Ferromagnet Simultaneous Allowance for Different Kinds of Anisotropy Ferromagnetic Resonance in a Polycrystal Independent-Grain and Strongly-Coupled Grain Approximations Influence of Porosity Antiferromagnets and Ferrites Antiferromagnetism and Ferrimagnetism Crystal and Magnetic Structures Equations of Motion and Energy Terms Ground States and Small Oscillations Antiferromagnetic Resonance Antiferromagnet with an Easy Axis of Anisotropy: Steady States Oscillations in Antiparallel State Oscillations in Noncollinear State Oscillations in Transverse and Arbitrarily Oriented Fields Antiferromagnet with Easy Plane of Anisotropy Magnetic Oscillations in Ferrimagnets Ground States of Two-Sublattice Ferrimagnet Oscillations in Antiparallel Ground State Oscillations in Noncollinear Ground State Damped and Forced Oscillations Fundamentals of Electrodynamics of Gyrotropic Media Equations General Equations and Boundary Conditions Equations for Bigyotropic Media Uniform Plane Waves General Relations Longitudinal Magnetization Transverse Magnetization Nonreciprocity Energy Relations Equation of Energy Balance Energy Losses Perturbation Method Gyrotropic Perturbation of a Waveguide Gyrotropic Perturbation of a Resonator Quasistatic Approximation Resonator with Walls of Real Metal Waveguides and Resonators with Gyrotropic Media. Microwave Ferrite Devices Waveguide with Longitudinally Magnetized Medium Circular Waveguide Circular Waveguide with Ferrite Rod Faraday Ferrite Devices Waveguide with Transversely Magnetized Ferrite Rectangular Waveguide Filled with Ferrite Rectangular Waveguide with Ferrite Plates Microwave Ferrite Devices Resonators with Gyrotropic Media Eigenoscillations and Forced Oscillations Waveguide Resonators Ferrite Resonators Use of Perturbation Method Waveguides and Waveguide Junctions with Ferrite Samples Ferrite Ellipsoid in a Waveguide Coupling of Orthogonal Waveguides. Ferrite Band-Pass Filters General Properties of Nonreciprocal Junctions Magnetostatic Waves and Oscillations Magnetostatic Approximation Nonexchange Magnetostatic Waves in Plates and Rods Volume Waves in Plates Surface Waves Magnetostatic Waves in Waveguides with Finite Cross Section Energy Flow and Losses Magnetostatic Waves in Ferrite Films: Excitation, Applications Magnetostatic Oscillations (Walker's Modes) Metallized Cylinder Sphere and Ellipsoid of Revolution Damping, Excitation, and Coupling Spin Waves Spin Waves in Unbounded Ferromagnet Energy and Effective Field of Exchange Interaction Dispersion Law Magnetization, Field Components, and Damping Spin Waves in Bounded Bodies Exchange Boundary Conditions Standing Spin Waves in Films Propagating Spin Waves in Films Spin Waves in Nonuniform Magnetic Fields Magnons Quantization of Magnetic Oscillations and Waves Thermal Magnons Elements of Microscopic Spin-Wave Theory Diagonalization of the Hamiltonian Discussion of the Dispersion Law Allowance for Dipole-Dipole Interaction and Anisotropy Interaction of Magnons Magnetic Oscillations and Waves in Unsaturated Ferromagnet Oscillations of Domain Walls Domain Walls and Domain Structures Equation of Motion of a Domain Wall Dynamic Susceptibility Ferromagnetic Resonance in Samples with Domain Structure Ellipsoid of Uniaxial Ferromagnet Sphere of Cubic Ferromagnet Nonuniform Modes in Unsaturated Samples Nonlinear Oscillations of Magnetization Ferromagnetic Resonance in Strong Alternating Fields Rigorous Solution of Equation of Motion Approximate Methods Harmonic Generation and Frequency Conversion Frequency Doubling Frequency Mixing Parametric Excitation of Magnetic Oscillations and Waves Nonlinear Coupling of Magnetic Modes Thresholds of Parametric Excitation under Transverse Pumping First-Order and Second-Order Instabilities Threshold Fields Effect of Pumping-Field Polarization Longitudinal and Oblique Pumping Longitudinal Pumping Effect of Nonuniformities Oblique Pumping Instability of Nonuniform Modes and Nonuniform Pumping Parametric Excitation of Magnetostatic Oscillations and Waves Ferrite Parametric Amplifier Nonuniform Pumping Above-Threshold State Reaction of Parametric Spin Waves on Pumping Phase Mechanism Nonlinear Damping Stability of the Above-Threshold State Nonlinear Microwave Ferrite Devices Spin-Spin Relaxation Relaxation Processes in Magnetically Ordered Substances Kinds of Relaxation Processes Methods of Theoretical Study Inherent Spin-Spin Processes Three-Magnon Splitting Three-Magnon Confluence Four-Magnon Scattering Inherent Processes for Uniform Precession Experimental Data Two-Magnon Processes Theory of Two-Magnon Processes Disorder in Distribution of Ions over Lattice Sites Anisotropy-Field Variation and Pores in Polycrystals Surface Roughness Magnetoelastic Coupling Elastic Properties and Magnetoelastic Interaction Elastic Waves and Oscillations Magnetoelastic Energy and Equations of Motion Effect of Elastic Stresses on Ferromagnetic Resonance Magnetoelastic Waves Normal Waves Damping and Excitation Magnetoelastic Waves in Nonuniform Steady Magnetic Field Parametric Excitation of Magnetoelastic Waves Longitudinal Pumping of Magnetoelastic Waves Parametric Excitation Caused by Magnetoelastic Coupling Elastic Pumping Spin-Lattice Relaxation Ionic Anisotropy and Relaxation Anisotropy Caused by Impurity Ions Energy Levels of Ions One-Ion Theory of Ferromagnetic-Resonance Anisotropy Near-Crossing Energy Levels Experimental Data Ion Relaxation Processes Transverse Relaxation Longitudinal (Slow) Relaxation Relaxation of Ionic-Level Populations Experimental Data Interaction of Magnetic Oscillations and Waves with Charge Carriers Effect of Charge Carriers in Semiconductors Damping of Magnetic Oscillations Caused by Conductivity Influence of Interionic Electron Transitions Interaction of Spin Waves with Charge Carriers Ferromagnetic Resonance and Spin Waves in Metals Thin-Film Model Theory without Allowance for Exchange Interaction Influence of Exchange Interaction Antiresonance Processes of Magnetic Relaxation Appendices Units and Constants Demagnetization Factors Dirac Delta Function and Kronecker Delta Symbol Bibliography Subject Index to the Bibliography Index

Magnon Spintronics : Fundamentals of Magnon-Based Computing

Abstract: This chapter addresses a selection of fundamental topics that form the basis of the magnon-based computing and are of primary importance for the further development of theconcept. It examines the transport of spin-wave-carried information in one and two dimensions that is required for the realization of logic elements and integrated magnon circuits is covered. The chapter discusses the converters between spin waves and electron currents. It provides a basic knowledge of spin waves in the most commonly used structure, a spin-wave waveguide in the form of a narrow strip. The main spin-wave characteristics can be obtained from the analysis of its dispersion relation, that is, the dependence of the wave frequency on its wavenumber k. Spin waves are usually studied in nanometer-thick and micrometer-wide waveguides and, several additional factors, which define spin-wave properties, should be considered. The fabrication of high-quality spin-wave waveguides in the form of magnetic strips is also one of the primary tasks in the field of magnonics.

Bose–Einstein condensation of quasi-equilibrium magnons at room temperature under pumping

Abstract: Bose–Einstein condensation (BEC), a form of matter first postulated in 1924, has famously been demonstrated in dilute atomic gases at ultra-low temperatures. Much effort is now being devoted to exploring solid-state systems in which BEC can occur. In theory semiconductor microcavities, where photons are confined and coupled to electronic excitations leading to the creation of polaritons, could allow BEC at standard cryogenic temperatures. Kasprzak et al. now present experiments in which polaritons are excited in such a microcavity. Above a critical polariton density, spontaneous onset of a macroscopic quantum phase occurs, indicating a solid-state BEC. BEC should also be possible at higher temperatures if coupling of light with solid excitations is sufficiently strong. Demokritov et al. have achieved just that, BEC at room temperature in a gas of magnons, which are a type of magnetic excitation. Bose–Einstein condensation, the formation of a collective quantum state of identical particles, called bosons, is observed at room temperature in a gas of magnons, which are a type of magnetic excitation. Bose–Einstein condensation1,2 is one of the most fascinating phenomena predicted by quantum mechanics. It involves the formation of a collective quantum state composed of identical particles with integer angular momentum (bosons), if the particle density exceeds a critical value. To achieve Bose–Einstein condensation, one can either decrease the temperature or increase the density of bosons. It has been predicted3,4 that a quasi-equilibrium system of bosons could undergo Bose–Einstein condensation even at relatively high temperatures, if the flow rate of energy pumped into the system exceeds a critical value. Here we report the observation of Bose–Einstein condensation in a gas of magnons at room temperature. Magnons are the quanta of magnetic excitations in a magnetically ordered ensemble of magnetic moments. In thermal equilibrium, they can be described by Bose–Einstein statistics with zero chemical potential and a temperature-dependent density. In the experiments presented here, we show that by using a technique of microwave pumping it is possible to excite additional magnons and to create a gas of quasi-equilibrium magnons with a non-zero chemical potential. With increasing pumping intensity, the chemical potential reaches the energy of the lowest magnon state, and a Bose condensate of magnons is formed.

Hybridizing ferromagnetic magnons and microwave photons in the quantum limit

Abstract: We demonstrate large normal-mode splitting between a magnetostatic mode (the Kittel mode) in a ferromagnetic sphere of yttrium iron garnet and a microwave cavity mode. Strong coupling is achieved in the quantum regime where the average number of thermally or externally excited magnons and photons is less than one. We also confirm that the coupling strength is proportional to the square root of the number of spins. A nonmonotonic temperature dependence of the Kittel-mode linewidth is observed below 1 K and is attributed to the dissipation due to the coupling with a bath of two-level systems.