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Thermaelastic properties of ramdom alloys from first-principles theory
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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2006 (English)In: Phys. Rev. B, Vol. 73, 104203- p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2006. Vol. 73, 104203- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-95714OAI: oai:DiVA.org:uu-95714DiVA: diva2:170032
Available from: 2007-04-04 Created: 2007-04-04 Last updated: 2012-03-30Bibliographically approved
In thesis
1. Computational Material Design: Diluted Magnetic Semiconductors for Spintronics
Open this publication in new window or tab >>Computational Material Design: Diluted Magnetic Semiconductors for Spintronics
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis deals with the application of ab-initio electronic structure calculations based on density functional theory for material design.

The correlation between magnetic properties and electronic structures has been investigated in detail for diluted magnetic semiconductors (DMS), which have promising application for spintronics devices. The point defects, acting as electron donor or electron acceptor, have been studied for their key role in mediating the long ranged ferromagnetic interaction between transition metal (TM) ions. The electron holes induced by electron acceptor are completely spin polarized in semiconductor and exhibit a very significant efficiency to the ferromagnetic coupling between TM ions. While the electron donor shows a negative effect to the ferromagnetism in the system. The common trend of magnetic interaction and electron charge transfer between TM ions and electron acceptors or electron donators have been outlined. The Coulomb correlation U of d electrons, which could change the energy levels of TM d band respective to the host semiconductor band, also shows a significant influence on the magnetic behavior in DMS.

The crystallography phase transition under high pressure has also been studied for the iron doped with light element, carbon. Our calculated results show that interstitial carbon defect has little effect on the iron's bcc to hcp phase transition under high pressure. The other carbon iron phases, like Fe3C, has also been studied in a wide pressure range.

We also present a first-principles description on the temperature dependence of elastic constant for solids. The total temperature effects are approximated as a sum of two separated parts, the thermal expansion contribution, which gives the normal linearly decreasing effect on the elastic constant with increasing temperature, and the electronic band contribution, which could lead anomalous behavior for thermal elastic constants.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 64 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 290
Keyword
Physics, Density functional theory, Diluted magnetic semiconductor, Ferromagnetism, Defect, Phase transition, High pressure, Thermal elastic constant, Fysik
Identifiers
urn:nbn:se:uu:diva-7800 (URN)978-91-554-6855-2 (ISBN)
Public defence
2007-04-26, Polhemsalen, Angstrom Laboratory, Box 530, Uppsala, 10:15
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Supervisors
Available from: 2007-04-04 Created: 2007-04-04Bibliographically approved

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Vitos, LeventeJohansson, BörjeAhuja, Rajeev

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