Search results for "Electron magnetic dipole moment"
showing 10 items of 30 documents
Heavy mass expansion, light-by-light scattering through pointlike quanta, and the anomalous magnetic moment of the muon
2003
Contributions from light-by-light scattering to ${(g}_{\ensuremath{\mu}}\ensuremath{-}2)/2,$ the anomalous magnetic moment of the muon, are mediated by the exchange of charged fermions or scalar bosons. Assuming large masses M, pointlike couplings for the virtual particles and employing the technique of large mass expansion, analytical results are obtained for virtual fermions and scalars in the form of a series in ${(m}_{\ensuremath{\mu}}{/M)}^{2}.$ This series is well convergent even for the case ${M=m}_{\ensuremath{\mu}}.$ For pointlike virtual fermions, the expansion confirms published analytical formulas. For virtual scalars, the result can be used to evaluate the contribution from poi…
Axionlike Particles, Lepton-Flavor Violation, and a New Explanation of aμ and ae
2020
Axionlike particles (ALPs) with lepton-flavor-violating couplings can be probed in exotic muon and tau decays. The sensitivity of different experiments depends strongly on the ALP mass and its couplings to leptons and photons. For ALPs that can be resonantly produced, the sensitivity of three-body decays such as μ→3e and τ→3μ exceeds by many orders of magnitude that of radiative decays like μ→eγ and τ→μγ. Searches for these two types of processes are therefore highly complementary. We discuss experimental constraints on ALPs with a single dominant lepton-flavor-violating coupling. Allowing for one or more such couplings offers qualitatively new ways to explain the anomalies related to the m…
Coupled stochastic dynamics of magnetic moment and anisotropy axis of a magnetic nanoparticle
2012
An algorithm is developed for numerical simulation of coupled stochastic dynamics of magnetic moment and magnetic anisotropy axis of a nanoparticle. Time-correlation functions of the magnetic moment and its components longitudinal and transverse to the magnetic anisotropy axis are calculated by averaging along the stochastic trajectory. The longitudinal and transverse relaxation times are found by fitting the time correlation functions. Existing theoretical relations derived by the effective field approach in the limit of small fields are confirmed. The time-correlation functions of magnetic moments of nanoparticles in dependence on their properties are calculated numerically for arbitrary …
Evaluation of the magnetic moments of radium isotopes
1990
Using the relativistic linked cluster many-body perturbation procedure we have obtained the hyperfine field at the nucleus of the Ra+ ion in the2S1/2 ground state. There is good agreement between the calculated magnetic moment of213Ra and the results of a recent Zeeman measurement by the collinear laser beam technique. Detailed comparison is carried out between our result and earlier ones.
On the magnetic dipole moment of the153Tb ground state
1981
Temperature dependence of the angular distribution anisotropy of the 212·0 keV gamma-ray following the decay of153Tb oriented in a gadolinium host was measured at temperatures from 16 to 70 mK. Magnetic dipole hyperfine splitting parameter a0 for153Tb(Gd) and magnetic dipole moment of the153Tb ground state were estimated to be ¦a0¦≧1·2×10−5 eV and ¦μ¦≧≧3·1 nuclear magnetons, respectively.
Field Dependence of the Electron Spin Relaxation in Quantum Dots
2005
Interaction of the electron spin with local elastic twists due to transverse phonons has been studied. Universal dependence of the spin relaxation rate on the strength and direction of the magnetic field has been obtained in terms of the electron gyromagnetic tensor and macroscopic elastic constants of the solid. The theory contains no unknown parameters and it can be easily tested in experiment. At high magnetic field it provides parameter-free lower bound on the electron spin relaxation in quantum dots.
Large orbital moments and internal magnetic fields in lithium nitridoferrate(I)
2002
The iron nitridometalates Li2[(Li(1-x)Fe(I)(x))N] display ferromagnetic ordering and spin freezing. Large magnetic moments up to 5.0mu(B)/Fe are found in the magnetization. In Mössbauer effect studies huge hyperfine magnetic fields up to 696 kOe are observed at specific Fe sites. These extraordinary fields and moments originate in an unusual ligand field splitting for those Fe species leading [within local spin density approximation (LSDA)] to a localized orbitally degenerate doublet. Including spin-orbit interaction and strong intra-atomic electron correlation (LDA+SO+U) gives rise to a large orbital momentum.
Self-consistency conditions for localized magnetic moments in a free electron gas
1969
The self-consistent conditions for a localized magnetic moment in a metal are studied in the case where the density of states of the host metal is free electron like. A method is outlined which in principle allows to determine self-consistently in the Hartree-Fock approximation the relevant parameters of the magnetic ground state of the system. A numerical example is approximately worked out to show how the theory gives reasonable answers in spite of the crudeness of some of the approximations used.
Evolution of Mixed Dirac Particles Interacting with an External Magnetic Field
2007
We study in the framework of relativistic quantum mechanics the evolution of a system of two Dirac neutrinos that mix with each other and have non-vanishing magnetic moments. The dynamics of this system in an external magnetic field is determined by solving the Pauli-Dirac equation with a given initial condition. We consider first neutrino spin-flavor oscillations in a constant magnetic field and derive an analytical expression for the transition probability of spin-flavor conversion in the limit of small magnetic interactions. We then investigate ultrarelativistic neutrinos in an transversal magnetic field and derive their wave functions and transition probabilities with no limitation for …
Correlation in the transition-metal-based Heusler compoundsCo2MnSiandCo2FeSi
2006
Half-metallic ferromagnets, such as the Heusler compounds with formula ${X}_{2}YZ$, are expected to show an integer value for the spin magnetic moment. In contrast to experiments, calculations give noninteger values in certain cases where the compounds are based on $X=\mathrm{Co}$. In order to explain deviations of the magnetic moment calculated for such compounds, the dependence of the electronic structure on the lattice parameter was studied theoretically. In the local density approximation (LDA), the minimum total energy of ${\mathrm{Co}}_{2}\mathrm{FeSi}$ is found for the experimental lattice parameter, but the calculated magnetic moment is approximately 12% too low. In addition, half-m…