Search query: Furdyna, J.. “Diluted magnetic semiconductors

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abstract: We review the physical properties of diluted magnetic semiconductors (DMS) of the type AII1 xMnxBVI (e.g. Cd1 xMnxSe, Hg1 xMnxTe) Crystallographic properties are discussed first, with emphasis on the common structural features which these materials have as a result of tetrahedral bonding. We then describe the band structure of the AII1 xMnxBVI alloys in the absence of an external magnetic field, stressing the close relationship of the sp electron bands in these materials to the band structure of the nonmagnetic AIIBVI 'parent' semiconductors. In addition, the characteristics of the narrow (nearly localized) band arising from the half filled Mn 3d5 shells are described, along with their profound effect on the optical properties of DMS. We then describe our present understanding of the magnetic properties of the AII1 xMnxBVI alloys. In particular, we discuss the mechanism of the Mn+ Mn+ exchange, which underlies the magnetism of these materials; we present an analytic formulation for the magnetic susc.
author_names: Jacek K Furdyna
title: Diluted magnetic semiconductors
year: 1988

abstract: Diluted magnetic semiconductors (DMSs) i.e. semiconducting crystals whose lattice is made up in part of substitutional magnetic ions (e.g. Cd/sub 1 x/Mn/sub x/Te, Hg/sub 1 x/Fe/sub x/Se, Zn/sub 1 x/Co/sub x/S) are reviewed. The focus is on materials of the type A/sub 1 x//sup II/ Mn/sub x/B/sup VI/ which are the most thoroughly understood. However, the similarities and differences between these materials and the A/sub 1 x//sup II/Fe/sub x/B/sup VI/ and A/sub 1 /sup II/Co/sub x/B/sup VI/ systems are discussed wherever information on the latter system is available. The band structure of the materials, which determines their basic semiconducting properties, is examined. Special attention is given to exchange interactions between the magnetic ions themselves (the d d interaction) and the interaction between the magnetic ions and band electrons (the sp d interaction) Magnetic phenomena in DMS alloys are considered. Special attention is given to the physics of layered structures, such as quantum wells and superlattices, involving DMS materials. The prospects of device applications made possible by the properties of DMS alloys are assessed.
author_names: Nitin Samarth

Jacek K Furdyna
title: Diluted magnetic semiconductors
year: 1990

abstract: Thin epitaxial films of the diluted magnetic semiconductor (DMS) GaMnAs have been studied by low energy muon spin rotation and relaxation (LE microSR) as well as by transport and magnetization measurement techniques. LE microSR allows measurements of the distribution of magnetic field on the nanometer scale inaccessible to traditional macroscopic techniques. The spatial inhomogeneity of the magnetic field is resolved: although homogeneous above Tc, below Tc the DMS consists of ferromagnetic and paramagnetic regions of comparable volumes. In the ferromagnetic regions the local field inhomogeneity amounts to 0.03 T.
author_names: Vyacheslav G Storchak

Dmitry G Eshchenko

Elvezio Morenzoni

Thomas Prokscha

Andreas Suter

Xinyu Liu

Jacek K Furdyna
title: Spatially resolved inhomogeneous ferromagnetism in (Ga,Mn)as diluted magnetic semiconductors: a microscopic study by muon spin relaxation.
venue: Physical review letters
year: 2008

abstract: This paper reviews the electrical, magnetic, and optical properties of diluted magnetic semiconductors (sometimes also referred to as 'semimagnetic' semiconductors) These materials are ternary semiconductor alloys whose lattice is made up in part of substitutional magnetic ions. Cd1 xMnxTe and Hg1 xMnxTe are examples of such systems. As semiconductors, these alloys display interesting and important properties, such as the variation of the energy gap and of effective mass with composition. They also exhibit magnetic properties which are interesting in their own right, e.g. a low temperature spin glass transition and magnon excitations. Most importantly, however, the presence of substitutional magnetic ions in these alloys leads to spin spin exchange interaction between the localized magnetic moments and the band electrons. This in turn has rather important consequences on band structure and on donor and acceptor states, leading to dramatic effects in quantum transport, impurity conduction, and magneto optics. Specifically, the presence of exchange interaction results in extremely large and temperature dependent g factors of electrons and holes; in gigantic values of Faraday rotation; in anomalously large negative magnetoresistance; and in the formation of the bound magnetic polaron.
author_names: Jacek K Furdyna
title: DILUTE MAGNETIC SEMICONDUCTORS: OTHER SPIN GLASSES C. Stassis, Chairperson Diluted magnetic semiconductors: An interface of semiconductor physics and magnetism (invited)
year: 1982

abstract: The spin of the carriers has so far played a minor role in semiconductor devices mainly because the semiconductors used for industrial applications, such as Si and GaAs, are nonmagnetic. On the other hand, the enhanced spin related phenomena have been realized in diluted magnetic semiconductors (DMS) to offer applications known as spintronics. Discovery of ferromagnetism (FM) in the canonical DMS GaMnAs films which have the benefit of being compatible with GaAs technology has led to intense studies of the FM in these materials for spintronics applications. Although there is an emerging consensus that the FM in DMS originates from the interaction between itinerant carriers and localized magnetic moments, the microscopic theory of FM in these materials is the subject of considerable debate [1] Theoretical models encounter major difficulties caused by the absence of experimental data on the distribution of the magnetic field in DMS on the nanometer scale because so far the FM properties of DMS have been studied mainly using traditional macroscopic integral techniques unable to produce spatially resolved information. Here we present direct experimental evidence for the inhomogeneous nature of the FM state in GaMnAs DMS. Using low energy positive muons as a local magnetic probe we are able to resolve spatial inhomogeneity of the magnetic field in the thin film: although homogeneous above Tc, DMS clearly consists of ferromagnetic and paramagnetic regions of the comparable volumes in the FM state.
author_names: Vyacheslav G Storchak

Dmitry G Eshchenko

Elvezio Morenzoni

Thomas Prokscha

Andreas Suter

Xianghua Liu

Jacek K Furdyna
title: P 74 Poster II Magnetic Semiconductors Spatially Resolved Inhomogeneous Ferromagnetism in Ga Mn As Diluted Magnetic Semiconductors
year: 2008

abstract: Diluted magnetic semiconductors (DMS) are semiconducting alloys containing a random distribution of substitutional magnetic ions (e.g. Mn+ in Cd1 xMnxSe) Magnetic properties of DMS such as spin glass behavior due to lattice frustration, magnon excitations in a random system of spins, superexchange, and short range antiferromagnetic order are of considerable interest in their own right. In addition, understanding these properties is important because they strongly influence the electronic phenomena in DMS via the sp d exchange interaction between the band electrons and the localized magnetic moments. We review the most recent results concerning magnetic susceptibility, Mn+ Mn+ nearest neighbor exchange, and magnetic short range order in these materials. On this basis, we can present a fairly complete and unified picture of magnetic properties of DMS. In addition, we point out some of the issues and challenges that lie ahead.
author_names: Jacek K Furdyna

Nitin Samarth
title: Magnetic properties of diluted magnetic semiconductors: A review (invited)
year: 1987

abstract: We review the crystallography, band structure, and optical, electrical, and magnetic properties of diluted magnetic semiconductors (DMS) with emphasis on ternary alloys of the type AII1 xMnxBVI (e.g. Hg1 xMnxTe) Considerable attention in the review is given to spectacular novel effects which arise from the selective enhancement of spin dependent properties due to exchange interaction between the localized magnetic moments (Mn+2) and band electrons. We then identify the major issues currently facing the field of DMS, and we discuss the major opportunities which these materials hold in store, both in the area of further scientific discoveries and in technological applications. In particular, we stress the need for a systematic concerted effort in the area of controlling impurities and defects in DMS, and we argue that exchange interaction in these materials offers an additional tool for studies in this area. We then describe, as examples of important future opportunities, the emerging field of Fe based D.
author_names: Jacek K Furdyna
title: Diluted magnetic semiconductors: Issues and opportunities
year: 1986

abstract: Publisher Summary This chapter discusses the crystal structure, composition, and materials preparation of diluted magnetic semiconductors. It reviews the crystal structure and composition of the various AII1 xMnxBVI alloys. It shows that this can be done in a unified way for both the zinc blende and wurtzite members of this group of materials. The chapter also describes the methods of preparation of bulk diluted magnetic semiconductors (DMS) crystals, including materials purification, the synthesis of starting binary compounds, and crystal growth. It discusses recent developments in the field of DMS, such as AII1 xMnxBVI epitaxial films and superlattices, AII1 xFexBVI alloys, and AIVBVI based DMS containing substitutional manganese or rare earth ions. Both crystal structures of the DMS zinc blende and wurtzite are very closely related in spite of the differences in symmetry, they are both formed with tetrahedral (s p3) bonding, involving the two valence s electrons of the group VI element and the six valence p electrons of the group VI element. Manganese is a transition metal with valence electrons corresponding to the 4s2 orbital. Although manganese differs from the group II elements by the fact that its 3d shell is only half filled, it can contribute its 4s2 electrons to the s p3 bonding and can, therefore, substitutionally replace the group II elements in the AIIBVI wurtzite or zinc blende structures.
author_names: Witold Giriat

Jacek K Furdyna
title: Chapter 1 Crystal Structure, Composition, and Materials Preparation of Diluted Magnetic Semiconductors
year: 1988

abstract: We report measurements of EPR in the magnetic semiconductors Cd1 xMnxTe and reanalyze earlier data. Experimentally we find (i) the room temperature linewidth increases as x is increased, (ii) the g value, obtained by reference to the zero of the derivative curve, is almost independent of x, (iii) each resonance line has a symmetric lineshape, and (iv) for each x the linewidth increases as T is reduced. These facts suggest that the resonances are not relaxation broadened but are, instead, inhomogeneously broadened. We model this inhomogeneity in terms of a Gaussian distribution of internal fields and show that there is a sharp change in the x dependence of the corresponding Gaussian widths at the percolation threshold. We also note that the temperature dependence of the linewidths follows an empirical form proposed earlier for metallic spin glasses.
author_names: David J Webb

S M Bhagat

Jacek K Furdyna
title: Electron paramagnetic resonance linewidths in diluted magnetic semiconductors: Cd1 xMnxTe
year: 1984

abstract: Abstract Localization of exciton wavefunctions in self assembled quantum dots (QDs) has been investigated using CdSe QDs embedded in ZnMnSe. This system was chosen so as to make use of the giant Zeeman splitting in the diluted magnetic semiconductor (DMS) ZnMnSe, which enables one to map how the exciton wavefunction is distributed between the QDs and the surrounding matrix. Two series of CdSe QDs in ZnMnSe were prepared for this investigation by molecular beam epitaxy (MBE) either by varying the CdSe coverage while keeping a constant Mn concentration in ZnMnSe; or by varying the Mn concentration in the matrix while maintaining a constant CdSe coverage. Photoluminescence (PL) experiments show a systematic evolution of the CdSe QDs with increasing CdSe coverage; and also reveal the role of Mn in nucleating "seeding" the self assembly of the QDs. By simultaneously measuring the Zeeman shifts of the PL peaks from both the CdSe QDs and their ZnMnSe matrix, we are able to extract information on exciton localization in the QDs and its dependence on the degree of development of the self assembled CdSe QDs with increasing CdSe coverage.
author_names: Sang Hoon Lee

Margaret Dobrowolska

Jacek K Furdyna
title: Zeeman mapping of exciton localization in self assembled CdSe quantum dots using diluted magnetic semiconductors
year: 2007