10,025 research outputs found
Finite-size versus Surface effects in nanoparticles
We study the finite-size and surface effects on the thermal and spatial
behaviors of the magnetisation of a small magnetic particle. We consider two
systems: 1) A box-shaped isotropic particle of simple cubic structure with
either periodic or free boundary conditions. This case is treated analytically
using the isotropic model of D-component spin vectors in the limit , including the magnetic field. 2) A more realistic particle (-FeO) of ellipsoidal (or spherical) shape with open boundaries.
The magnetic state in this particle is described by the anisotropic classical
Dirac-Heisenberg model including exchange and dipolar interactions, and bulk
and surface anisotropy. This case is dealt with by the classical Monte Carlo
technique. It is shown that in both systems finite-size effects yield a
positive contribution to the magnetisation while surface effects render a
larger and negative contribution, leading to a net decrease of the
magnetisation of the small particle with respect to the bulk system. In the
system 2) the difference between the two contributions is enhanced by surface
anisotropy. The latter also leads to non saturation of the magnetisation at low
temperatures, showing that the magnetic order in the core of the particle is
perturbed by the magnetic disorder on the surface. This is confirmed by the
profile of the magnetisation.Comment: 6 pages of RevTex including 4 Figures, invited paper to 3rd
EuroConference on Magnetic Properties of Fine Nanoparticles, Barcelona,
October 9
Three-dimensional rotation of even-even triaxial nuclei
With the self-consistent three-dimensional cranked Hartree-Fock-Bogoliubov
(3d-cranked HFB) method, various types of rotational motion near the yrast line
are investigated in an even-even nucleus in the mass region
(Ce). The possibilities of chiral rotations,
tilted-rotations, and dynamical aspects of these rotations are discussed
through the analysis of the 3d-cranked HFB solutions. Although a stable planar
solution of the chiral rotation is obtained, an aplanar chiral configuration is
found to be unstable when triaxial deformation is treated self-consistently.Comment: 4 pages, 3 figures; accepted for publication in Phys. Lett.
Summer Preview of the 2007 Annual Meeting October 24-27, 2007
Summer Preview of the Annual Meetin
Nonlinear Terms of MHD Equations for Homogeneous Magnetized Shear Flow
We have derived the full set of MHD equations for incompressible shear flow
of a magnetized fluid and considered their solution in the wave-vector space.
The linearized equations give the famous amplification of slow magnetosonic
waves and describe the magnetorotational instability. The nonlinear terms in
our analysis are responsible for the creation of turbulence and self-sustained
spectral density of the MHD (Alfven and pseudo-Alfven) waves. Perspectives for
numerical simulations of weak turbulence and calculation of the effective
viscosity of accretion disks are shortly discussed in k-space.Comment: 13 pages, no figures; AIP Conference Proceedings 1356, Proceedings of
the School and Workshop on Space Plasma Physics (1--12 September 2010, Kiten,
Bulgaria), American Institute of Physics, Melville, NY, 201
Mid-Western Educational Research Association 2007 Annual Meeting, October 24-27, 2007
Call for Proposal
- …