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Ferromagnetism in Cu-doped ZnO from first-principles theory
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
2006 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 7, 075206- p.Article in journal (Refereed) Published
Abstract [en]

Using the first-principles method based on the density functional theory, we have studied the electronic structure and the ferromagnetic stability in Cu-doped ZnO. The system shows the half-metallic ground state and the high ferromagnetic stability for all the calculated Cu concentrations within the generalized gradient approximation (GGA). The delocalized holes induced by O 2p and Cu 3d hybridization are found to be very efficient to mediate the ferromagnetic exchange interaction. While going beyond the GGA, the ferromagnetic stability as a function of the Coulomb correlation U shows a sudden decrease when U=3 eV where the system becomes an insulating ground state. By doping the p-type or n-type defects, the holes can be increased or compensated. The n-type defect, such as O vacancy, Zn interstitial, or H interstitial decreases the ferromagnetic stability, while the p-type defect, such as Zn vacancy, increases the ferromagnetic stability. By keeping the system to be the metallic ground state, the defect of the Zn vacancy could retain the high ferromagnetic stability of the system even in the case of U.

Place, publisher, year, edition, pages
2006. Vol. 74, no 7, 075206- p.
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-95708DOI: 10.1103/PhysRevB.74.075206ISI: 000240238800049OAI: oai:DiVA.org:uu-95708DiVA: diva2:170026
Available from: 2007-04-04 Created: 2007-04-04 Last updated: 2012-03-05Bibliographically 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.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 290
Physics, Density functional theory, Diluted magnetic semiconductor, Ferromagnetism, Defect, Phase transition, High pressure, Thermal elastic constant, Fysik
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
Available from: 2007-04-04 Created: 2007-04-04Bibliographically approved

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Ahuja, Rajeev
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