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Search Results: 1 - 10 of 142 matches for " Dietl "
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Manipulation with spin ordering in ferromagnetic semiconductors
Dietl, Tomasz;
Brazilian Journal of Physics , 2004, DOI: 10.1590/S0103-97332004000400005
Abstract: a short overview is given of recent advances in the field of carrier-controlled ferromagnetism in mn-based iii-v and ii-vi diluted magnetic semiconductors and their nanostructures. the tailoring of domain structures and magnetic anisotropy by strain engineering and confinement is described. experiments demonstrating the tunability of tc by light and electric field are presented.
Lecture Notes on Semiconductor Spintronics
Tomasz Dietl
Physics , 2007,
Abstract: These informal lecture notes describe the progress in semiconductor spintronics in a historic perspective as well as in a comparison to achievements of spintronics of ferromagnetic metals. After outlining motivations behind spintronic research, selected results of investigations on three groups of materials are presented. These include non-magnetic semiconductors, hybrid structures involving semiconductors and ferromagnetic metals, and diluted magnetic semiconductors either in paramagnetic or ferromagnetic phase. Particular attention is paid to the hole-controlled ferromagnetic systems whose thermodynamic, micromagnetic, transport, and optical properties are described in detail together with relevant theoretical models.
Interplay between carrier localization and magnetism in diluted magnetic and ferromagnetic semiconductors
Tomasz Dietl
Physics , 2007, DOI: 10.1143/JPSJ.77.031005
Abstract: The presence of localized spins exerts a strong influence on quantum localization in doped semiconductors. At the same time carrier-mediated interactions between the localized spins are modified or even halted by carriers' localization. The interplay of these effects is discussed for II-VI and III-V diluted magnetic semiconductors. This insight is exploited to interpret the complex dependence of resistance on temperature, magnetic field, and concentration of valence-band holes in (Ga,Mn)As. In particular, high field negative magnetoresistance results from the orbital weak localization effect. The resistance maximum and the associated negative magnetoresistance near the Curie temperature are assigned to the destructive influence of preformed ferromagnetic bubbles on the "antilocalization" effect driven by disorder-modified carrier-carrier interactions. These interactions account also for the low-temperature increase of resistance. Furthermore, the sensitivity of conductance to spin splitting and to scattering by spin disorder may explain resistance anomalies at coercive fields, where relative directions of external and molecular fields change.
Origin of ferromagnetic response in diluted magnetic semiconductors and oxides
Tomasz Dietl
Physics , 2007, DOI: 10.1088/0953-8984/19/16/165204
Abstract: This paper reviews the present understanding of the origin of ferromagnetic response of diluted magnetic semiconductors and diluted magnetic oxides as well as in some nominally magnetically undoped materials. It is argued that these systems can be grouped into four classes. To the first belong composite materials in which precipitations of a known ferromagnetic, ferrimagnetic or antiferromagnetic compound account for magnetic characteristics at high temperatures. The second class forms alloys showing chemical nano-scale phase separation into the regions with small and large concentrations of the magnetic constituent. To the third class belong (Ga,Mn)As, heavily doped p-(Zn,Mn)Te, and related semiconductors. In these solid solutions the theory built on p-d Zener's model of hole-mediated ferromagnetism and on either the Kohn-Luttinger kp theory or the multi-orbital tight-binding approach describes qualitatively, and often quantitatively many relevant properties. Finally, in a number of carrier-doped DMS and DMO a competition between long-range ferromagnetic and short-range antiferromagnetic interactions and/or the proximity of the localisation boundary lead to an electronic nano-scale phase separation.
Origin and control of ferromagnetism in dilute magnetic semiconductors and oxides
Tomasz Dietl
Physics , 2007, DOI: 10.1063/1.2832613
Abstract: The author reviews the present understanding of the hole-mediated ferromagnetism in magnetically doped semiconductors and oxides as well as the origin of high temperature ferromagnetism in materials containing no valence band holes. It is argued that in these systems spinodal decomposition into regions with a large and a small concentration of magnetic component takes place. This self-organized assembling of magnetic nanocrystals can be controlled by co-doping and growth conditions. Functionalities of these multicomponent systems are described together with prospects for their applications in spintronics, nanoelectronics, photonics, plasmonics, and thermoelectrics.
Ferromagnetic semiconductors
Tomasz Dietl
Physics , 2002, DOI: 10.1088/0268-1242/17/4/310
Abstract: The current status and prospects of research on ferromagnetism in semiconductors are reviewed. The question of the origin of ferromagnetism in europium chalcogenides, chromium spinels and, particularly, in diluted magnetic semiconductors is addressed. The nature of electronic states derived from 3d of magnetic impurities is discussed in some details. Results of a quantitative comparison between experimental and theoretical results, notably for Mn-based III-V and II-VI compounds, are presented. This comparison demonstrates that the current theory of the exchange interactions mediated by holes in the valence band describes correctly the values of Curie temperatures T_C magnetic anisotropy, domain structure, and magnetic circular dichroism. On this basis, chemical trends are examined and show to lead to the prediction of semiconductor systems with T_C that may exceed room temperature, an expectation that are being confirmed by recent findings. Results for materials containing magnetic ions other than Mn are also presented emphasizing that the double exchange involving hoping through d states may operate in those systems.
Why ferromagnetic semiconductors?
Tomasz Dietl
Physics , 2002,
Abstract: Rapid development of information technologies originates from the exponential increase in the density of information that can be processed, stored, and transfer by the unit area of relevant devices. There is, however, a growing amount of evidences that the progress achieved in this way approaches its limits. Various novel ideas put forward to circumvent barriers ahead are described. Particular attention is paid to those concepts which propose to exploit electron or nuclear spins as the information carriers. Here, ferromagnetic semiconductors of III-V or II-VI compounds containing a sizable concentration of transition metals appear as outstanding spintronic materials.
Ferromagnetism in semiconductors and oxides: prospects from a ten years' perspective
Tomasz Dietl
Physics , 2011, DOI: 10.1038/nmat2898
Abstract: Over the last decade the search for compounds combining the resources of semiconductors and ferromagnets has evolved into an important field of materials science. This endeavour has been fuelled by continual demonstrations of remarkable low-temperature functionalities found for ferromagnetic structures of (Ga,Mn)As, p-(Cd,Mn)Te, and related compounds as well as by ample observations of ferromagnetic signatures at high temperatures in a number of non-metallic systems. In this paper, recent experimental and theoretical developments are reviewed emphasising that, from the one hand, they disentangle many controversies and puzzles accumulated over the last decade and, on the other, offer new research prospects.
Spin dynamics of a confined electron interacting with magnetic or nuclear spins: A semiclassical approach
Tomasz Dietl
Physics , 2014, DOI: 10.1103/PhysRevB.91.125204
Abstract: A physically transparent and mathematically simple semiclassical model is employed to examine dynamics in the central-spin problem. The results reproduce a number of previous findings obtained by various quantum approaches and, at the same time, provide information on the electron spin dynamics and Berry's phase effects over a wider range of experimentally relevant parameters than available previously. This development is relevant to dynamics of bound magnetic polarons and spin dephasing of an electron trapped by an impurity or a quantum dot, and coupled by a contact interaction to neighboring localized magnetic impurities or nuclear spins. Furthermore, it substantiates the applicability of semiclassical models to simulate dynamic properties of spintronic nanostructures with a mesoscopic number of spins.
Spin order manipulations in nanostructures of II-VI ferromagnetic semiconductors
Tomasz Dietl
Physics , 2003, DOI: 10.1016/j.jmmm.2003.12.323
Abstract: An overview of recent studies on ferromagnetism in Cr- and Mn-based II-VI diluted magnetic semiconductors is presented emphasizing differences in underlying exchange mechanisms. Examples of manipulations with spin ordering by carrier density, dimensionality, light, and electric field are given.
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