Dias, Manuel dos Santos (2011) Ab-initio theory of the magnetic properties of heterogeneous nanostructures. PhD thesis, University of Warwick.

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Abstract

This thesis presents a general formalism for a Density Functional Theory description
of the magnetic state of a heterogeneous system, from its paramagnetic high-temperature state to the magnetically ordered ground state. The key ingredient is
the identification of localised magnetic moments as emergent electronic degrees of
freedom, and the evolution of their orientations under a classical spin Hamiltonian
dictated by the underlying electronic structure, computed using Multiple Scattering
Theory. The magnetic interactions are contained in the spin-spin correlation function,
derived in a linear response approach, and are fully anisotropic, as relativistic
effects are accounted for.
A range of applications is given. A Mn monolayer on the W(001) is shown
to favour a cycloidal spin spiral as ground state, with a well-defined rotational
sense due to unidirectional anisotropic interactions. The antiferromagnetism of Mn
monolayers on X(111), with X = Pd, Pt, Ag and Au, is analysed, and the triangular
Néel state is shown to possess a well-defined chirality pattern. Calculations for
bulk zinc{blende MnSb characterise the half-metallic state as being robust against magnetic disorder; this particular polymorph was discovered in epitaxial form by
experimentalists at the University of Warwick, and shows promise for spintronics
applications. Bulk Co in the hcp and fcc structure reveals the strong feedback between
the magnitude of the spin moment and the degree of magnetic order, through
the corresponding electronic structure. To conclude, an FeRh film embedded in V
is considered. The magnetisation profile corresponding to the imposed antiferromagnetic
order is computed self-consistently, and shows the stabilisation of the Fe
layers close to the interface with V by those in the interior of the film.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QC Physics
Library of Congress Subject Headings (LCSH):	Density functionals, Magnetism, Nanostructures
Official Date:	September 2011
Dates:	Date Event September 2011 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Staunton, Julie B.
Sponsors:	Fundação para a Ciência e a Tecnologia (FCT) (SFRH/BD/35738/2007)
Extent:	xii, 126 leaves : ill., charts
Language:	eng
URI:	http://wrap.warwick.ac.uk/id/eprint/45835

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