Dynamical correlations from mobile vortices in two-dimensional easy-plane ferromagnets

Journal Article · Sat Dec 31 23:00:00 EST 1988 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.39.591· OSTI ID:6434235

Mertens, F G; Bishop, A R; Wysin, G M; Kawabata, C

Assuming an ideal gas of unbound vortices above the Kosterlitz-Thouless transition temperature, we calculate the dynamic form factors for both the in-plane and out-of-plane correlations. In both cases central peaks are predicted which are, however, produced by quite different mechanisms, depending on whether the correlations are globally or locally sensitive to the presence of the vortices. For the in-plane correlations the wave-vector dependencies of the width and intensity of the peaks are very well supported by the central peaks, which are observed in a combined Monte Carlo molecular-dynamics simulation of the XY model. Therefore the parameters of the theory (root-mean-square vortex velocity and mean vortex-vortex separation) can be fitted and turn out to agree rather well with independent theoretical estimates. Recent inelastic neutron-scattering experiments on the in-plane correlations for BaCo/sub 2/(AsO/sub 4/)/sub 2/ and Rb/sub 2/CrCl/sub 4/ also show central peaks. Their temperature and wave-vector dependencies are consistent with our results, but their widths are larger than the theoretical estimates. Therefore, these peaks are interpreted to result, at least partially, from a gas of vortices. For the out-of-plane correlations our simulations also show a central peak. However so far it cannot be identified unequivocally as a vortex contribution.

• Research Organization: Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
• OSTI ID: 6434235
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 39:1; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

656002* -- Condensed Matter Physics-- General Techniques in Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANGULAR MOMENTUM
CRYSTAL MODELS
FERROMAGNETIC MATERIALS
HEISENBERG MODEL
MAGNETIC MATERIALS
MATERIALS
MATHEMATICAL MODELS
MONTE CARLO METHOD
NONLINEAR PROBLEMS
PARTICLE PROPERTIES
PHYSICAL PROPERTIES
SPIN
SPIN WAVES
THERMODYNAMIC PROPERTIES
THERMODYNAMICS
TRANSITION TEMPERATURE
VORTICES