Rate of magnetization reversal due to nucleation of soliton-antisoliton pairs at point-like defects

Title
Rate of magnetization reversal due to nucleation of soliton-antisoliton pairs at point-like defects
Publication Date
2008
Author(s)
Loxley, Peter
( author )
OrcID: https://orcid.org/0000-0003-3659-734X
Email: ploxley@une.edu.au
UNE Id une-id:ploxley
Type of document
Journal Article
Language
en
Entity Type
Publication
Publisher
American Physical Society
Place of publication
United States of America
DOI
10.1103/PhysRevB.77.144424
UNE publication id
une:21382
Abstract
The rate of magnetization reversal due to the nucleation of soliton-antisoliton pairs at point-like defects is found for a uniaxial ferromagnet in an applied magnetic field. Point-like defects are considered as local variations in the magnetic anisotropy over a length scale smaller than the domain-wall width. A weak magnetic field applied along the easy axis causes the magnetization to become metastable, and the lowest activation barrier for reversal involves the nucleation of a soliton-antisoliton pair pinned to a point-like defect. Formulas are derived for the activation energy and field of reversal, and the reversal-rate prefactor is calculated using Langer's theory for the decay of a metastable state. As the applied field tends to zero, the lowest activation energy is found to be exactly half that of an unpinned soliton-antisoliton pair, and results from the formation of a spatially nonuniform metastable state when the defect strength become large. The smallest field of reversal is exactly half of the anisotropy field. The reversal-rate prefactor is found to increase with the number of point-like defects but decreases with increase in the defect strength due to a decrease in the activation entropy when translational symmetry is broken by the point-like defects, and soliton-antisoliton pairs become more strongly localized to the pinning sites.
Link
Citation
Physical Review B: covering condensed matter and materials physics, 77(14), p. 1-14
ISSN
2469-9969
1098-0121
2469-9977
Start page
1
End page
14

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