Titill:  Energy surface and lifetime of magnetic skyrmions 
Höfundur: 

Útgáfa:  201711 
Tungumál:  Enska 
Háskóli/Stofnun:  Háskóli Íslands University of Iceland 
Svið:  Verkfræði og náttúruvísindasvið (HÍ) School of Engineering and Natural Sciences (UI) 
Deild:  Raunvísindastofnun (HÍ) Science Institute (UI) Raunvísindadeild (HÍ) Faculty of Physical Sciences (UI) 
Birtist í:  Journal of Magnetism and Magnetic Materials; 
ISSN:  03048853 
DOI:  10.1016/j.jmmm.2017.10.100 
Efnisorð:  Condensed Matter Physics; DzyaloshinskiiMoriya interaction; Skyrmions; Magnetism; Þéttefnisfræði; Segulmagn; Skammtasviðsfræði 
URI:  https://hdl.handle.net/20.500.11815/536 
Tilvitnun:V.M. Uzdin et al., Energy surface and lifetime of magnetic skyrmions, Journal of Magnetism and Magnetic Materials (2017), https://doi.org/10.1016/j.jmmm.2017.10.100


Útdráttur:The stability of skyrmions in various environments is estimated by analyzing the multidimensional surface
describing the energy of the system as a function of the directions of the magnetic moments in the
system. The energy is given by a Heisenberglike Hamiltonian including terms representing
DzyaloshinskiiMoriya interaction, anisotropy energy and interaction with an external magnetic field.
Local minima on this surface correspond to the ferromagnetic and skyrmion states. Minimum energy
paths (MEP) between the minima are calculated using the geodesic nudged elastic band method. The
maximum energy along an MEP corresponds to a first order saddle point on the energy surface and gives
an estimate of the activation energy for the magnetic transition, such as creation and annihilation of a
skyrmion. The preexponential factor in the Arrhenius law for the rate, the socalled attempt frequency,
is estimated within harmonic transition state theory where the eigenvalues of the Hessian at the saddle
point and the local minima are used to characterize the shape of the energy surface. For some degrees of
freedom, socalled ‘‘zero modes”, the energy of the system remains invariant. They need to be treated
separately and give rise to temperature dependence of the attempt frequency. As an example application
of this general theory, the lifetime of a skyrmion in a track of finite width for a PdFe overlayer on a Ir(1 1
1) substrate is calculated as a function of track width and external magnetic field. Also, the effect of nonmagnetic
impurities is studied. Various MEPs for annihilation inside a track, via the boundary of a track
and at an impurity are presented. The attempt frequency as well as the activation energy has been calculated
for each mechanism to estimate the transition rate as a function of temperature


Leyfi:2017 Elsevier B.V. All rights reserved.
