Title:
Spin-transfer Torque in Magnetic Nanostructures

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dc.contributor.advisor Zangwill, Andrew
dc.contributor.author Xiao, Jiang en_US
dc.contributor.committeeMember Chou, Mei-yin
dc.contributor.committeeMember First, Phillip
dc.contributor.committeeMember Sa De Melo, Carlos
dc.contributor.committeeMember Stiles, Mark
dc.contributor.department Physics en_US
dc.date.accessioned 2006-09-01T19:27:05Z
dc.date.available 2006-09-01T19:27:05Z
dc.date.issued 2006-05-30 en_US
dc.description.abstract This thesis consists of three distinct components: (1) a test of Slocnzewski's theory of spin-transfer torque using the Boltzmann equation, (2) a comparison of macrospin models of spin-transfer dynamics in spin valves with experimental data, and (3) a study of spin-transfer torque in continuously variable magnetization. Slonczewski developed a simple circuit theory for spin-transfer torque in spin valves with thin spacer layer. We developed a numerical method to calculate the spin-transfer torque in a spin valve using Boltzmann equation. In almost all realistic cases, the circuit theory predictions agree well with the Boltzmann equation results. To gain a better understanding of experimental results for spin valve systems, current-induced magnetization dynamics for a spin valve are studied using a single-domain approximation and a generalized Landau-Lifshitz-Gilbert equation. Many features of the experiment were reproduced by the simulations. However, there are two significant discrepancies: the current dependence of the magnetization precession frequency, and the presence and/or absence of a microwave quiet magnetic phase with a distinct magnetoresistance signature. Spin-transfer effects in systems with continuously varying magnetization also have attracted much attention. One key question is under what condition is the spin current adiabatic, i.e., aligned to the local magnetization. Both quantum and semi-classical calculations of the spin current and spin-transfer torque are done in a free-electron Stoner model. The calculation shows that, in the adiabatic limit, the spin current aligns to the local magnetization while the spin density does not. The reason is found in an effective field produced by the gradient of the magnetization in the wall. Non-adiabatic effects arise for short domain walls, but their magnitude decreases exponentially as the wall width increases. en_US
dc.description.degree Ph.D. en_US
dc.format.extent 2371477 bytes
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/11513
dc.language.iso en_US
dc.publisher Georgia Institute of Technology en_US
dc.subject Spintronics en_US
dc.subject Spin current
dc.subject Spin transfer torque
dc.subject Spin valve
dc.subject Domain wall
dc.subject Magnetization dynamics
dc.subject.lcsh Nanotechnology en_US
dc.subject.lcsh Spintronics en_US
dc.title Spin-transfer Torque in Magnetic Nanostructures en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Zangwill, Andrew
local.contributor.corporatename College of Sciences
local.contributor.corporatename School of Physics
relation.isAdvisorOfPublication 6676cdfd-9b38-49e9-9e56-5eb0b50c6590
relation.isOrgUnitOfPublication 85042be6-2d68-4e07-b384-e1f908fae48a
relation.isOrgUnitOfPublication 2ba39017-11f1-40f4-9bc5-66f17b8f1539
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