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Investigations of domain-wall motion using atomistic spin dynamics
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
2015 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this thesis, current driven domain-wall motion is studied using atomistic simulations with the exchange coupling modeled by the Heisenberg Hamiltonian under the nearest-neighbor approximation. The investigations may be divided into two parts, each concerned with how different aspects of the systems affect the domain-wall motion. The first part deals with domain-wall width dependence of the velocity in a three dimensional geometry with simple cubic crystal structure and uniaxial anisotropy. Results from this part showed that the velocity has a minor domain-wall width dependence. For a fixed current density, the velocity increased with domain-wall width, though only from 61.5 a/ns to 64.5 a/ns as the domain-wall width was increased from 3 to 25 atoms.

The second part of the investigations deals with phenomena involving mixed cubic and uniaxial anisotropy, the non-adiabaticity parameter as well as the geometry of the system. The discussion includes an account of how the spin-transfer and cubic anisotropy torques contribute to the motion for different values of the non-adiabaticity parameter. In comparing a one dimensional atomic chain and a three dimensional system with simple cubic crystal structure, but otherwise with the same material properties, results showed a difference in how the two systems responded to currents. This difference is not accounted for by the micromagnetic theory, and its origin was unable to be determined.

Place, publisher, year, edition, pages
2015. , 54 p.
Series
UPTEC F, ISSN 1401-5757 ; 15010
Keyword [en]
spin-transfer torques, non-adiabaticity, Walker breakdown, atomistic simulations
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-247556OAI: oai:DiVA.org:uu-247556DiVA: diva2:796867
Educational program
Master Programme in Engineering Physics
Supervisors
Examiners
Available from: 2015-03-24 Created: 2015-03-20 Last updated: 2015-03-26Bibliographically approved

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