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Magnetic percolation in diluted magnetic semiconductors
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
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2004 (English)In: Physical Review Letters, ISSN 0031-9007, Vol. 93, no 13, 137202- p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate that the magnetic properties of diluted magnetic semiconductors are dominated by short ranged interatomic exchange interactions that have a strong directional dependence. By combining first principles calculations of interatomic exchange interactions with a classical Heisenberg model and Monte Carlo simulations, we reproduce the observed critical temperatures of a broad range of diluted magnetic semiconductors. We also show that agreement between theory and experiment is obtained only when the magnetic atoms are randomly positioned. This suggests that the ordering of diluted magnetic semiconductors is heavily influenced by magnetic percolation, and that the measured critical temperatures should be very sensitive to details in the sample preparation, in agreement with observations.

Place, publisher, year, edition, pages
2004. Vol. 93, no 13, 137202- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-92830DOI: 10.1103/PhysRevLett.93.137202OAI: oai:DiVA.org:uu-92830DiVA: diva2:166133
Available from: 2005-04-08 Created: 2005-04-08 Last updated: 2012-03-27Bibliographically approved
In thesis
1. Electronic Structure and Statistical Methods Applied to Nanomagnetism, Diluted Magnetic Semiconductors and Spintronics
Open this publication in new window or tab >>Electronic Structure and Statistical Methods Applied to Nanomagnetism, Diluted Magnetic Semiconductors and Spintronics
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is divided in three parts. In the first part, a study of materials aimed for spintronics applications is presented. More specifically, calculations of the critical temperature in diluted magnetic semiconductors (DMS) and half-metallic ferromagnets are presented using a combination of electronic structure and statistical methods. It is shown that disorder and randomness of the magnetic atoms in DMS materials play a very important role in the determination of the critical temperature.

The second part treats materials in reduced dimensions. Studies of multilayer and trilayer systems are presented. A theoretical model that incorporates interdiffusion in a multilayer is developed that gives better agreement with experimental observations. Using Monte Carlo simulations, the observed magnetic properties in the trilayer system Ni/Cu/Co at finite temperatures are qualitatively reproduced.

In the third part, electronic structure calculations of complex Mn-based compounds displaying noncollinear magnetism are presented. The calculations reproduce with high accuracy the observed magnetic properties in these compounds. Furthermore, a model based on the electronic structure of the necessary conditions for noncollinear magnetism is presented.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. x+70 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 32
Keyword
Materials science, spintronics, magnetism, Monte Carlo, critical temperature, exchange interactions, percolation, disorder, noncollinear, electronic structure, Materialvetenskap
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-5732 (URN)91-554-6202-2 (ISBN)
Public defence
2005-04-29, Room 4001, Ångströmlaboratoriet, 10:15
Opponent
Supervisors
Available from: 2005-04-08 Created: 2005-04-08 Last updated: 2013-06-20Bibliographically approved

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Bergqvist, LarsEriksson, Olle

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