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Exchange interactions and critical temperatures in diluted magnetic semiconductors
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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2004 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 16, no 48, 5571- p.Article in journal (Refereed) Published
Abstract [en]

A first-principles approach to magnetic properties of diluted magnetic semiconductors (DMS) is presented that is based on the local spin-density approximation (LSDA) as implemented in the framework of the tight-binding linear muffin-tin orbital method, while the effect of randomness is described by the coherent potential approximation. Application of a real-space Green-function formalism yields the exchange pair interactions between distant magnetic atoms that are needed for quantitative studies of magnetic excitations including the Curie temperatures. We have found that the pair exchange interactions exhibit a strong directional dependence and are exponentially damped with increasing distance between magnetic atoms due to disorder and the half-metallic character of the DMS. As a case study we consider (Ga, Mn) As, (Ga, Mn)N, and (Zn, Cr)Te alloys. The calculations demonstrate that inclusion of disorder and, in particular, realistic distances among magnetic impurities, are needed to obtain critical temperatures which are in good agreement with available experiments.

Place, publisher, year, edition, pages
2004. Vol. 16, no 48, 5571- p.
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-92833DOI: 10.1088/0953-8984/16/48/013OAI: oai:DiVA.org:uu-92833DiVA: diva2:166136
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.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 32
Materials science, spintronics, magnetism, Monte Carlo, critical temperature, exchange interactions, percolation, disorder, noncollinear, electronic structure, Materialvetenskap
National Category
Materials Engineering
urn:nbn:se:uu:diva-5732 (URN)91-554-6202-2 (ISBN)
Public defence
2005-04-29, Room 4001, Ångströmlaboratoriet, 10:15
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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