摘要:

AbstractThis paper deals with a theoretical model which describes the effect of Majorana transitions on the frequency of a cesium atomic clock. In contrast to the explanations given in the past, the phase correlation between the individual successive excitations in inhomogeneous magnetic fields and the microwave resonator are for the first time taken into account.The π transitions with the selection rule ΔF= 1, Δm= ± 1 are of particular importance. The theory allows experimental results obtained in the past with the CSX apparatus, in particular the large frequency shifts observed, to be interpreted. The effect on the determination of the uncertainty of primary atomic clocks will be discus

ISSN:0003-3804    

DOI:10.1002/andp.19935050502

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractHigh‐resolution normal photoemission (ARPE) spectra have been recorded for Cu3Au(111) with the use of polarized synchrotron and rare‐gas resonance radiation in the photon energy range from 9 to 27 eV. It is for the first time that dispersions of the gold‐like bands have been found experimentally. Using a fully relativistic layer‐KKR photoemission formalism, occupied and unoccupied bands as well as one‐step‐model photoemission spectra have been calculated. The comparison of calculated spectra with experimental ones and the observation of direct‐transition resonances upon photon energy near the Brillouin zone‐center reveal a shift of the unoccupied ground‐state bands by about +2.5 eV (self‐energy shift). The direct‐transition structures in the experimental spectra have been exploited to determine the dispersions of the occupied bands along the [111] direction (Aline inkspace). In order to determine the wave vector of the experimental direct transitions we used as final state that calculated unoccupied band along [111], which also exists in pure copper and gold up to about 20 eV above the Fermi energy (“unfolded” band structure), shifted by + 2.5 eV. The experimental occupied bands with Cu character are in very good agreement with theory after shifting the latter by about 0.3 eV to lower energy, whereas somewhat bigger discrepancies exis

ISSN:0003-3804    

DOI:10.1002/andp.19935050503

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe salient features of the total low energy inelastic electron scattering cross section in transition metals are described by a constant term σ0plus a term σdthat is proportional to the number of unoccupiedd‐orbitals. This simple model predicts that low energy electrons transmitted through a ferromagnetic ultrathin film acquire a transport spin polarizationa(χ). Using the ratio σ0/σdas the only adjustable parameter, the model predicts the enhancement of the spin polarization of the low energy cascade electrons as well as a(χ) in reasonable agreement with the existing observations on Fe, Co and Ni. A detector for electron spin polarizationPbased on the spin dependent transmission of electrons through ferromagnetic material is proposed which should be superior to existingP‐detectors by 1–2 orders o

ISSN:0003-3804    

DOI:10.1002/andp.19935050504

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe temperature dependence of magnetic domain walls in ferromagnetic systems with strong exchange coupling and weak lattice anisotropy is studied assuming that the thermal influence results mainly from the temperature dependence of the magnetization. We obtain that in lattices with an uniaxial symmetry like Co the wall width increases with temperature, but stays finite up to the Curie temperatureTc. In contrary, for a cubic lattice like Fe the wall width diverges forT→Tc, if only the lattice anisotropy is taken into account. The shape of the domain walls is not conserved, since atTcthe wall is determined only by the lowest order of anisotropy. In addition, the temperature dependence of a domain wall width for a thin magnetic film is determined. Using a special symmetry, we obtain a diverging wall width at a temperature markedly lower thanTc. However, the consideration of additional domain wall modes should modify this resul

ISSN:0003-3804    

DOI:10.1002/andp.19935050505

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractGrad‐type approaches introduce an ansatz involving tensor Hermite functions with coefficients expresed in terms of moments of the ansatz. This formalism in usual form yields terms linear in first‐order spatial derivatives in kinetic equations for the moments. Such terms disagree with alternative statistical derivations and phenomenological arguments. This disagreement is removed if different ansatzes are used to calculate entropy and moment equations. These are non‐unique, and so Grad theory, while providing theoretical expressions for transport coefficients, does not serve uniquely to determine the structure of phenomenological equa

ISSN:0003-3804    

DOI:10.1002/andp.19935050506

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

ISSN:0003-3804    

DOI:10.1002/andp.19935050501

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY