Dynamic correlations in the classical two-dimensional antiferromagnetic Heisenberg model with easy-plane symmetry

Journal Article · Thu Oct 31 23:00:00 EST 1991 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.44.10066· OSTI ID:6218804

Voelkel, A R; Wysin, G M; Bishop, A R; Mertens, F G ^[1]

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1. Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico (USA)

We investigate the dynamics of the two-dimensional antiferromagnetic Heisenberg model with easy-plane exchange symmetry. We develop a phenomenology of spin-wave and vortex excitations and calculate their contributions to the dynamical correlation functions {ital S}{sup {alpha}{alpha}}({bold q},{omega}), {alpha}={ital x},{ital y},{ital z}. The vortex shape depends explicitly on an exchange anisotropy parameter {lambda} and changes from a mainly in-plane structure below a critical {lambda}{sub {ital c}} to a shape with well-established {ital z} components around the vortex center above {lambda}{sub {ital c}}. In this paper we will discuss only the case {lambda}{lt}{lambda}{sub {ital c}}, where the system behaves almost like the pure {ital XY} model. The general properties of the dynamical behavior of the spin waves and vortices below the Kosterlitz-Thouless transition temperature {ital T}{sub KT} have been widely examined for the ferromagnetic {ital XY} model, and do not change much in the antiferromagnet (although here we have two magnon branches according to the two different spin sublattices). Our main interest is focused on the unbound vortices just above {ital T}{sub KT}. Assuming a dilute gas of ballistically moving vortices, we obtain central peaks in {ital S}{sup {alpha}{alpha}}({bold q},{omega}) similar to the ferromagnetic case, but in some cases at different positions in {bold q} space depending on whether the static vortex structure or the deviation from it due to a finite velocity dominates the correlations. These results are compared with a combined Monte Carlo--molecular-dynamics simulation on a 100{times}100 square lattice.

• OSTI ID: 6218804
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 44:18; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
ALKALI METAL COMPOUNDS
ANTIFERROMAGNETIC MATERIALS
ARSENATES
ARSENIC COMPOUNDS
CARBON
CHLORIDES
CHLORINE COMPOUNDS
CHROMIUM CHLORIDES
CHROMIUM COMPLEXES
CHROMIUM COMPOUNDS
CLATHRATES
COMPLEXES
COPPER CHLORIDES
COPPER COMPLEXES
COPPER COMPOUNDS
COPPER FLUORIDES
COPPER HALIDES
CORRELATION FUNCTIONS
CRYSTAL MODELS
ELEMENTAL MINERALS
ELEMENTS
FLUORIDES
FLUORINE COMPOUNDS
FUNCTIONS
GRAPHITE
HALIDES
HALOGEN COMPOUNDS
HEISENBERG MODEL
MAGNETIC MATERIALS
MATERIALS
MATHEMATICAL MODELS
MINERALS
NONMETALS
OXYGEN COMPOUNDS
POTASSIUM COMPOUNDS
RUBIDIUM COMPOUNDS
SPIN WAVES
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
TWO-DIMENSIONAL CALCULATIONS