The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Ingrid Mertig - One of the best experts on this subject based on the ideXlab platform.
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Orbital Magnetic Moment of Magnons
Physical review letters, 2020Co-Authors: Robin R. Neumann, Alexander Mook, Jürgen Henk, Ingrid MertigAbstract:In experiments and their interpretation usually the spin Magnetic Moment of magnons is considered. In this Letter, we identify a complementing orbital Magnetic Moment of magnons brought about by spin-orbit coupling. Our microscopic theory uncovers that spin magnetization M^{S} and orbital magnetization M^{O} are independent quantities; they are not necessarily collinear. Even when the total spin Moment is compensated due to antiferromagnetism, M^{O} may be nonzero. This scenario of orbital weak ferromagnetism is realized in paradigmatic kagome antiferromagnets with Dzyaloshinskii-Moriya interaction. We demonstrate that magnets exhibiting a magnonic orbital Moment are omnipresent and propose transport experiments for probing it.
William H. Matthaeus - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Moment nonconservation in magnetohydrodynamic turbulence models.
Physical Review E, 2012Co-Authors: S. Dalena, Antonella Greco, A. F. Rappazzo, R. L. Mace, William H. MatthaeusAbstract:The fundamental assumptions of the adiabatic theory do not apply in presence of sharp field gradients as well as in presence of well developed magnetohydrodynamic turbulence. For this reason in such conditions the Magnetic Moment $\mu$ is no longer expected to be constant. This can influence particle acceleration and have considerable implications in many astrophysical problems. Starting with the resonant interaction between ions and a single parallel propagating electroMagnetic wave, we derive expressions for the Magnetic Moment trapping width $\Delta \mu$ (defined as the half peak-to-peak difference in the particle Magnetic Moment) and the bounce frequency $\omega_b$. We perform test-particle simulations to investigate Magnetic Moment behavior when resonances overlapping occurs and during the interaction of a ring-beam particle distribution with a broad-band slab spectrum. We find that Magnetic Moment dynamics is strictly related to pitch angle $\alpha$ for a low level of Magnetic fluctuation, $\delta B/B_0 = (10^{-3}, \, 10^{-2})$, where $B_0$ is the constant and uniform background Magnetic field. Stochasticity arises for intermediate fluctuation values and its effect on pitch angle is the isotropization of the distribution function $f(\alpha)$. This is a transient regime during which Magnetic Moment distribution $f(\mu)$ exhibits a characteristic one-sided long tail and starts to be influenced by the onset of spatial parallel diffusion, i.e., the variance $$ grows linearly in time as in normal diffusion. With strong fluctuations $f(\alpha)$ isotropizes completely, spatial diffusion sets in and $f(\mu)$ behavior is closely related to the sampling of the varying Magnetic field associated with that spatial diffusion.Comment: 13 pages, 10 figures, submitted to PR
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Magnetic Moment nonconservation in magnetohydrodynamic turbulence models.
Physical review. E Statistical nonlinear and soft matter physics, 2012Co-Authors: S. Dalena, Antonella Greco, A. F. Rappazzo, R. L. Mace, William H. MatthaeusAbstract:The fundamental assumptions of the adiabatic theory do not apply in the presence of sharp field gradients or in the presence of well-developed magnetohydrodynamic turbulence. For this reason, in such conditions the Magnetic Moment μ is no longer expected to be constant. This can influence particle acceleration and have considerable implications in many astrophysical problems. Starting with the resonant interaction between ions and a single parallel propagating electroMagnetic wave, we derive expressions for the Magnetic Moment trapping width Δμ (defined as the half peak-to-peak difference in the particle Magnetic Moments) and the bounce frequency ω(b). We perform test-particle simulations to investigate Magnetic Moment behavior when resonance overlapping occurs and during the interaction of a ring-beam particle distribution with a broadband slab spectrum. We find that the changes of Magnetic Moment and changes of pitch angle are related when the level of Magnetic fluctuations is low, δB/B(0) = (10(-3),10(-2)), where B(0) is the constant and uniform background Magnetic field. Stochasticity arises for intermediate fluctuation values and its effect on pitch angle is the isotropization of the distribution function f(α). This is a transient regime during which Magnetic Moment distribution f(μ) exhibits a characteristic one-sided long tail and starts to be influenced by the onset of spatial parallel diffusion, i.e., the variance grows linearly in time as in normal diffusion. With strong fluctuations f(α) becomes completely isotropic, spatial diffusion sets in, and the f(μ) behavior is closely related to the sampling of the varying Magnetic field associated with that spatial diffusion.
Andrew Steinmetz - One of the best experts on this subject based on the ideXlab platform.
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Strong fields and neutral particle Magnetic Moment dynamics
Plasma Physics and Controlled Fusion, 2018Co-Authors: Martin Formanek, Stefan Evans, Johann Rafelski, Andrew Steinmetz, Cheng Tao YangAbstract:Interaction of Magnetic Moment of point particles with external electroMagnetic fields experiences unresolved theoretical and experimental discrepancies. In this work we point out several issues within the relativistic quantum mechanics and the QED and we describe effects related to a new covariant classical model of Magnetic Moment dynamics. Using this framework we explore the invariant acceleration experienced by neutral particles coupled to an external plane wave field through the Magnetic Moment: we study the case of ultra relativistic Dirac neutrinos with Magnetic Moment in the range of $10^{-11}$ to $10^{-20}$ $\mu_\mathrm{B}$; and we address the case of slowly moving neutrons. We explore how critical accelerations for neutrinos can be experimentally achieved in laser-pulse interactions. The radiation of accelerated neutrinos can serve as an important test distinguishing between Majorana and Dirac nature of neutrinos.
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Relativistic dynamics of point Magnetic Moment
The European Physical Journal C, 2018Co-Authors: Johann Rafelski, Martin Formanek, Andrew SteinmetzAbstract:The covariant motion of a classical point particle with Magnetic Moment in the presence of (external) electroMagnetic fields is revisited. We are interested in understanding extensions to the Lorentz force involving point particle Magnetic Moment (Stern–Gerlach force) and how the spin precession dynamics is modified for consistency. We introduce spin as a classical particle property inherent to Poincare symmetry of space-time. We propose a covariant formulation of the Magnetic force based on a ‘Magnetic’ 4-potential and show how the point particle Magnetic Moment relates to the Amperian (current loop) and Gilbertian (Magnetic monopole) descriptions. We show that covariant spin precession lacks a unique form and discuss the connection to $$g-2$$ anomaly. We consider the variational action principle and find that a consistent extension of the Lorentz force to include Magnetic spin force is not straightforward. We look at non-covariant particle dynamics, and present a short introduction to the dynamics of (neutral) particles hit by a laser pulse of arbitrary shape.
Robin R. Neumann - One of the best experts on this subject based on the ideXlab platform.
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Orbital Magnetic Moment of Magnons
Physical review letters, 2020Co-Authors: Robin R. Neumann, Alexander Mook, Jürgen Henk, Ingrid MertigAbstract:In experiments and their interpretation usually the spin Magnetic Moment of magnons is considered. In this Letter, we identify a complementing orbital Magnetic Moment of magnons brought about by spin-orbit coupling. Our microscopic theory uncovers that spin magnetization M^{S} and orbital magnetization M^{O} are independent quantities; they are not necessarily collinear. Even when the total spin Moment is compensated due to antiferromagnetism, M^{O} may be nonzero. This scenario of orbital weak ferromagnetism is realized in paradigmatic kagome antiferromagnets with Dzyaloshinskii-Moriya interaction. We demonstrate that magnets exhibiting a magnonic orbital Moment are omnipresent and propose transport experiments for probing it.
S. Dalena - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Moment nonconservation in magnetohydrodynamic turbulence models.
Physical Review E, 2012Co-Authors: S. Dalena, Antonella Greco, A. F. Rappazzo, R. L. Mace, William H. MatthaeusAbstract:The fundamental assumptions of the adiabatic theory do not apply in presence of sharp field gradients as well as in presence of well developed magnetohydrodynamic turbulence. For this reason in such conditions the Magnetic Moment $\mu$ is no longer expected to be constant. This can influence particle acceleration and have considerable implications in many astrophysical problems. Starting with the resonant interaction between ions and a single parallel propagating electroMagnetic wave, we derive expressions for the Magnetic Moment trapping width $\Delta \mu$ (defined as the half peak-to-peak difference in the particle Magnetic Moment) and the bounce frequency $\omega_b$. We perform test-particle simulations to investigate Magnetic Moment behavior when resonances overlapping occurs and during the interaction of a ring-beam particle distribution with a broad-band slab spectrum. We find that Magnetic Moment dynamics is strictly related to pitch angle $\alpha$ for a low level of Magnetic fluctuation, $\delta B/B_0 = (10^{-3}, \, 10^{-2})$, where $B_0$ is the constant and uniform background Magnetic field. Stochasticity arises for intermediate fluctuation values and its effect on pitch angle is the isotropization of the distribution function $f(\alpha)$. This is a transient regime during which Magnetic Moment distribution $f(\mu)$ exhibits a characteristic one-sided long tail and starts to be influenced by the onset of spatial parallel diffusion, i.e., the variance $$ grows linearly in time as in normal diffusion. With strong fluctuations $f(\alpha)$ isotropizes completely, spatial diffusion sets in and $f(\mu)$ behavior is closely related to the sampling of the varying Magnetic field associated with that spatial diffusion.Comment: 13 pages, 10 figures, submitted to PR
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Magnetic Moment nonconservation in magnetohydrodynamic turbulence models.
Physical review. E Statistical nonlinear and soft matter physics, 2012Co-Authors: S. Dalena, Antonella Greco, A. F. Rappazzo, R. L. Mace, William H. MatthaeusAbstract:The fundamental assumptions of the adiabatic theory do not apply in the presence of sharp field gradients or in the presence of well-developed magnetohydrodynamic turbulence. For this reason, in such conditions the Magnetic Moment μ is no longer expected to be constant. This can influence particle acceleration and have considerable implications in many astrophysical problems. Starting with the resonant interaction between ions and a single parallel propagating electroMagnetic wave, we derive expressions for the Magnetic Moment trapping width Δμ (defined as the half peak-to-peak difference in the particle Magnetic Moments) and the bounce frequency ω(b). We perform test-particle simulations to investigate Magnetic Moment behavior when resonance overlapping occurs and during the interaction of a ring-beam particle distribution with a broadband slab spectrum. We find that the changes of Magnetic Moment and changes of pitch angle are related when the level of Magnetic fluctuations is low, δB/B(0) = (10(-3),10(-2)), where B(0) is the constant and uniform background Magnetic field. Stochasticity arises for intermediate fluctuation values and its effect on pitch angle is the isotropization of the distribution function f(α). This is a transient regime during which Magnetic Moment distribution f(μ) exhibits a characteristic one-sided long tail and starts to be influenced by the onset of spatial parallel diffusion, i.e., the variance grows linearly in time as in normal diffusion. With strong fluctuations f(α) becomes completely isotropic, spatial diffusion sets in, and the f(μ) behavior is closely related to the sampling of the varying Magnetic field associated with that spatial diffusion.
