5,420 research outputs found
Critical dynamics of dipolar ferromagnets
The dynamical scaling functions for ferromagnets with dipolar interactions are computed by mode coupling theory above the critical temperature Tc. On the basis of this theory we explain apparently conflicting features of neutron scattering experiments on EuO, EuS and Fe. The position of the crossover from isotropic to dipolar critical dynamics is determined and further experiments are proposed
Renormalized field theory for the static crossover in dipolar ferromagnets
A field theoretical description for the static crossover in dipolar ferromagnets is presented. New non leading critical exponents for the longitudinal static susceptibility are identified and the existence and magnitude of the dip in the effective critical exponent of the transverse susceptibility found by matching techniques is scrutinized
Critical dynamics of ferromagnets
The crossover in the dynamics from isotropic to dipolar critical behaviour has been a matter of debate over many years. We review a mode coupling theory for dipolar ferromagnets which gives a unified explanation of the seemingly contradictory experimental situation. The shape functions, the scaling functions for the damping coefficients and the precise position of the crossover are computed. Below Tc only the exchange interaction is taken into account
On the critical dynamics of ferromagnets
The dynamic scaling functions for ferromagnets above and below the critical temperature are determined using mode coupling theory. Below the critical temperature we study isotropic ferromagnets taking into account the exchange interaction only and give the first numerical solution of the resulting mode coupling equations. In the paramagnetic phase we examine how the critical dynamics is modified by the addition of the dipoledipole interaction. On the basis of this theory we are able to explain in a unifying fashion the results of different experimental methods; i.e.: neutron scattering, hyperfine interaction and electron-spin resonance. Predictions for new experiments are made
Factors Affecting Doctoral Educational Leadership Program Selection
Although recruitment has always been vital to sustained university admissions, it is true perhaps now more than ever as traditional public university programs face fierce competition for students from digitally-delivered and for-profit programs. Competition is fierce at every level of higher education, including the doctoral level. As competition has increased, so have the number of universities offering doctoral degrees (U.S. Department of Education [DOE], 2013). In 2011, Texas ranked fourth behind California, Florida, and North Carolina in the number of doctoral degrees granted in the United States. Furthennore, the number of doctoral degrees conferred in Texas grew from 8,959 in 2008 to 9,705 in 201 l(DOE, 2013) - a similar trend to most states across the nation that year. Of those, Texas has 26 public and private institutions - not including online universities - granting doctoral degrees in Educational Leadership (DOE, 2013). With the increase in traditional, online, and for-profit doctoral programs in Texas, existing programs may need to reevaluate efforts to stay competitive to survive in the current climate
Structure and energetics of Si(111)-(5x2)-Au
We propose a new structural model for the Si(111)-(5x2)-Au reconstruction.
The model incorporates a new experimental value of 0.6 monolayer for the
coverage of gold atoms, equivalent to six gold atoms per 5x2 cell. Five main
theoretical results, obtained from first-principles total-energy calculations,
support the model. (1) In the presence of silicon adatoms the periodicity of
the gold rows spontaneously doubles, in agreement with experiment. (2) The
dependence of the surface energy on the adatom coverage indicates that a
uniformly covered phase is unstable and will phase-separate into empty and
covered regions, as observed experimentally. (3) Theoretical scanning tunneling
microscopy images are in excellent agreement with experiment. (4) The
calculated band structure is consistent with angle-resolved photoemission
spectra; analysis of their correspondence allows the straightforward assignment
of observed surface states to specific atoms. (5) The calculated activation
barrier for diffusion of silicon adatoms along the row direction is in
excellent agreement with the experimentally measured barrier.Comment: 11 pages, 7 figures, also available with higher-resolution figures
from http://cst-www.nrl.navy.mil/users/erwin/ausi111.v5.pd
Instrumentation of the variable-angle magneto-optic ellipsometer and its application to M-O media and other non-magnetic films
A new and comprehensive dielectric tensor characterization instrument is presented for characterization of magneto-optical recording media and non-magnetic thin films. Random and systematic errors of the system are studied. A series of TbFe, TbFeCo, and Co/Pt samples with different composition and thicknesses are characterized for their optical and magneto-optical properties. The optical properties of several non-magnetic films are also measured
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