Inertia, diffusion, and dynamics of a driven skyrmion

Skyrmions recently discovered in chiral magnets are a promising candidate for magnetic storage devices because of their topological stability, small size (~ 3-100 nm), and ultralow threshold current density (~ 10 super(6) A/m super(2)) to drive their motion. However, the time-dependent dynamics has...

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Bibliographic Details
Published in:Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2014-11, Vol.90 (17), Article 174434
Main Authors: Schütte, Christoph, Iwasaki, Junichi, Rosch, Achim, Nagaosa, Naoto
Format: Article
Language:English
Subjects:
Condensed matter
Damping
Density
Devices
Dynamics
Hypothetical particles
Inertial
Mathematical analysis
Particle theory
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Summary:Skyrmions recently discovered in chiral magnets are a promising candidate for magnetic storage devices because of their topological stability, small size (~ 3-100 nm), and ultralow threshold current density (~ 10 super(6) A/m super(2)) to drive their motion. However, the time-dependent dynamics has hitherto been largely unexplored. Here, we show, by combining the numerical solution of the Landau-Lifshitz-GiIbert equation and the analysis of a generalized Thiele's equation, that inertial effects are almost completely absent in skyrmion dynamics driven by a time-dependent current. In contrast, the response to time-dependent magnetic forces and thermal fluctuations depends strongly on frequency and is described by a large effective mass and a (anti-) damping depending on the acceleration of the skyrmion. Thermal diffusion is strongly suppressed by the cyclotron motion and is proportional to the Gilbert damping coefficient alpha . This indicates that the skyrmion position is stable, and its motion responds to the time-dependent current without delay or retardation even if it is fast. These findings demonstrate the advantages of skyrmions as information carriers.
ISSN:1098-0121
1550-235X
DOI:10.1103/PhysRevB.90.174434