SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Sadowski Janusz) srt2:(2010-2014)"

Sökning: WFRF:(Sadowski Janusz) > (2010-2014)

  • Resultat 1-50 av 56
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Adell, Johan, 1980, et al. (författare)
  • Electron spectroscopic studies of nanowires formed by (GaMn)As growth on GaAs(111)B
  • 2011
  • Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 151:11, s. 850-854
  • Tidskriftsartikel (refereegranskat)abstract
    • Valence band photoemission with photon energies around the Mn2p excitation threshold has been used to study the development of nanowires catalyzed by MnAs particles. A gradual change in the spectra with increasing nanowire length is observed, such that the resonant photoemission eventually dominates over the Auger decay channel. The change is ascribed to dilution of Mn, showing that Mn is transferred from the MnAs particles into the nanowires. (C) 2011 Elsevier Ltd. All rights reserved.
  •  
2.
  • Adell, Johan, 1980, et al. (författare)
  • Thermal diffusion of Mn through GaAs overlayers on (Ga, Mn)As
  • 2011
  • Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 23:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermally stimulated diffusion of Mn through thin layers of GaAs has been studied by x-ray photoemission. (Ga, Mn)As samples with 5 at% Mn were capped with 4, 6 and 8 monolayer (ML) GaAs, and Mn diffusing through the GaAs was trapped on the surface by means of amorphous As. It was found that the out-diffusion is completely suppressed for an 8 ML thick GaAs film. The short diffusion length is attributed to an electrostatic barrier formed at the (Ga, Mn)As/GaAs interface.
  •  
3.
  • Di Marco, I., et al. (författare)
  • Electron correlations in Mn(x)Ga(1–x)As as seen by resonant electron spectroscopy and dynamical mean field theory
  • 2013
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 6-2645
  • Tidskriftsartikel (refereegranskat)abstract
    • After two decades since the discovery of ferromagnetism in manganese-doped gallium arsenide, its origin is still debated, and many doubts are related to the electronic structure. Here we report an experimental and theoretical study of the valence electron spectrum of manganese-doped gallium arsenide. The experimental data are obtained through the differences between off- and on-resonance photo emission data. The theoretical spectrum is calculated by means of a combination of density-functional theory in the local density approximation and dynamical mean field theory, using exact diagonalization as impurity solver. Theory is found to accurately reproduce measured data and illustrates the importance of correlation effects. Our results demonstrate that the manganese states extend over a broad range of energy, including the top of the valence band, and that no impurity band splits-off from the valence band edge, whereas the induced holes seem located primarily around the manganese impurity.
  •  
4.
  • Kanski, Janusz, 1946, et al. (författare)
  • Mn-induced modifications of Ga 3d photoemission from (Ga, Mn)As: evidence for long range effects
  • 2012
  • Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 24:43, s. 1-435802
  • Tidskriftsartikel (refereegranskat)abstract
    • Using synchrotron based photoemission, we have investigated the Mn-induced changes in Ga 3d core level spectra from as-grown Ga(1-x)Mn(x)As. Although Mn is located in Ga substitutional sites, and therefore does not have any Ga nearest neighbors, the impact of Mn on the Ga core level spectra is pronounced even at Mn concentrations in the region of 0.5%. The analysis shows that each Mn atom affects a volume corresponding to a sphere with around 1.4 nm diameter.
  •  
5.
  • Laukkanen, P., et al. (författare)
  • Ultrathin (1x2)-Sn layer on GaAs(100) and InAs(100) substrates : A catalyst for removal of amorphous surface oxides
  • 2011
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:23, s. 231908-1-231908-3
  • Tidskriftsartikel (refereegranskat)abstract
    • Amorphous surface oxides of III-V semiconductors are harmful in many contexts of device development. Using low-energy electron diffraction and photoelectron spectroscopy, we demonstrate that surface oxides formed at Sn-capped GaAs(100) and InAs(100) surfaces in air are effectively removed by heating. This Sn-mediated oxide desorption procedure results in the initial well-defined Sn-stabilized (1x2) surface even for samples exposed to air for a prolonged time. Based on ab initio calculations we propose that the phenomenon is due to indirect and direct effects of Sn. The Sn-induced surface composition weakens oxygen adsorption.
  •  
6.
  • Ulfat, I., et al. (författare)
  • Effects of nonuniform Mn distribution in (Ga,Mn)As
  • 2014
  • Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 89:4, s. art no 045312-
  • Tidskriftsartikel (refereegranskat)abstract
    • Resonant in situ photoemission from Mn 3d states in Ga(1−x)MnxAs is reported for Mn concentrations down to the very dilute level of 0.1%. Concentration-dependent spectral features are analyzed on the basis of first-principles calculations for systems with selected impurity positions as well as for random alloys. Effects of direct Mn-Mn interaction are found for concentrations as low as 2.5%, and are ascribed to statistical (nonuniform) distribution of Mn atoms.
  •  
7.
  • Ulfat, Intikhab, 1966, et al. (författare)
  • Electron Spectroscopic Studies of Homogenous (GaMn)As layers
  • 2012
  • Ingår i: Advanced Materials Research. - 1662-8985 .- 1022-6680. - 9783037853634 ; 463-464, s. 380-384
  • Konferensbidrag (refereegranskat)abstract
    • By incorporating magnetism into semiconductors, it may possibly be viable to enhance the functionality of materials. An exceptionally important material in this context is GaAs, which can be doped with Mn atoms. (GaMn)As has fascinated research community as a promising candidate for spintronic application. It is quite appealing due to both its compatibility with existing HI-V technology and great progress in improving its magnetic properties. Being fabricated by low temperature molecular beam epitaxy (LT-MBE), due to thermal instability at elevated temperatures, the material contains a high density of various defects compensating Mn acceptors. It is a well-established fact that the ferromagnetic state of (GaMn)As can be stabilized via post growth annealing. Nevertheless, in general, the annealed (GaMn)As layers do not remain useful for further epitaxial overgrowth that might be included in multilayer structure. We present a summary of our investigations regarding the synchrotron-based characterization of (GaMn)As layers grown via molecular beam epitaxy carried out at the Swedish National Facility of Synchrotron Radiation-the MAX-lab aiming at the reduction of the density of Mn interstitial and increase in the content of Mn.
  •  
8.
  •  
9.
  • Andrearczyk, Tomasz, et al. (författare)
  • Remnant magnetoresistance effect at the intersection of two ferromagnetic (Ga,Mn)As nanowires
  • 2011
  • Ingår i: Physica Status Solidi. B: Basic Research. - : Wiley. - 0370-1972. ; 248:7, s. 1587-1591
  • Tidskriftsartikel (refereegranskat)abstract
    • Cross-like nanostructures composed of two perpendicular ferromagnetic (Ga,Mn)As nanowires were fabricated using electron-beam lithography patterning. Nanostructures of different orientations with respect to the crystallographic axes of the parent (Ga,Mn)As epitaxial layer were studied. Electrical resistance of individual nanowires as a function of applied magnetic field were investigated at low temperatures. Low-field magnetoresistance (MR) of the nanowires exhibits hysteresis-like behaviour and related remnant resistance in zero magnetic field. These effects are explained in terms of magnetic domain walls (DWs) pinned at the wires intersection, which contribute to the wire resistance. The DW resistivity, which depends on the degree of spin misalignment in the wall, has been determined to be of the order of 1 Omega mu m(2). High-field MR has, in turn, allowed determining the lithography-induced anisotropy field for the nanowires of different crystallographic orientations. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  •  
10.
  • Bak-Misiuk, J., et al. (författare)
  • Pressure Variation of the Strain State of MnAs Nanoclusters Embedded in GaAs
  • 2012
  • Ingår i: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 121:4, s. 903-905
  • Tidskriftsartikel (refereegranskat)abstract
    • Granular GaAs:(Mn,Ga)As films were prepared by annealing at 500 degrees C under ambient and enhanced hydrostatic pressure (1.1 GPa), of Ga1-xMnxAs/GaAs layers (x = 0.025, 0.03, 0.04, 0.05 and 0.063) grown at 230 degrees C by molecular beam epitaxy method. Distinct influence of enhanced hydrostatic pressure applied during sample annealing on strain state of inclusions was found. An increase of lattice distortion and of strain of inclusions for the samples treated under hydrostatic pressure is related to different bulk moduli of GaAs and of MnAs
  •  
11.
  • Bak-Misiuk, J., et al. (författare)
  • Variation of strain in granular GaAs:MnAs layers
  • 2013
  • Ingår i: Crystallography Reports. - 1063-7745. ; 58:7, s. 998-1001
  • Tidskriftsartikel (refereegranskat)abstract
    • Granular GaAs(MnAs) layers with different Mn concentration and various layer thickness were grown by MBE method and subjected to annealing at 500A degrees C under ambient and enhanced hydrostatic pressure. Distinct influence of hydrostatic pressure applied during annealing on strain state of layers as well as on hexagonal MnAs inclusions was found. Pressure induced strain of inclusions is related to different bulk moduli of GaAs and of hexagonal MnAs. Formation of hexagonal inclusions depends on concentration of Mn in interstitial position in as-grown samples.
  •  
12.
  • Di Marco, Igor, et al. (författare)
  • Electron correlations in MnxGa1-xAs as seen by resonant electron spectroscopy and dynamical mean field theory
  • 2013
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 4, s. 6-
  • Tidskriftsartikel (refereegranskat)abstract
    • After two decades since the discovery of ferromagnetism in manganese-doped gallium arsenide, its origin is still debated, and many doubts are related to the electronic structure. Here we report an experimental and theoretical study of the valence electron spectrum of manganese-doped gallium arsenide. The experimental data are obtained through the differences between off- and on-resonance photo emission data. The theoretical spectrum is calculated by means of a combination of density-functional theory in the local density approximation and dynamical mean field theory, using exact diagonalization as impurity solver. Theory is found to accurately reproduce measured data and illustrates the importance of correlation effects. Our results demonstrate that the manganese states extend over a broad range of energy, including the top of the valence band, and that no impurity band splits-off from the valence band edge, whereas the induced holes seem located primarily around the manganese impurity.
  •  
13.
  • Dynowska, E., et al. (författare)
  • Structural and magnetic properties of GaSb:MnSb granular layers
  • 2011
  • Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 80:10, s. 1051-1057
  • Konferensbidrag (refereegranskat)abstract
    • The results of structural and magnetic characterization of GaMnSb layers grown on GaSb(0 0 1) and GaAs(1 1 1) substrates are presented. The presence of hexagonal, highly oriented MnSb inclusions embedded in GaSb matrix has been demonstrated. The lattice parameters of these inclusions were the same as those for bulk MnSb for the layers grown on GaSb(1 0 0) substrate while for the layers grown on GaAs(1 1 1) the MnSb inclusions were strained. The influence of a presence of MnSb clusters on the lattice parameter of GaSb matrix has been demonstrated. It was confirmed that in all cases the MnSb clusters exhibit a ferromagnetic: behavior at room temperature. (C) 2011 Elsevier Ltd. All rights reserved.
  •  
14.
  • Dziawa, P., et al. (författare)
  • Defect Free PbTe Nanowires Grown by Molecular Beam Epitaxy on GaAs(111)B Substrates
  • 2010
  • Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 10:1, s. 109-113
  • Tidskriftsartikel (refereegranskat)abstract
    • The molecular beam epitaxial growth of PbTe nanowires oil GaAs(111)B substrates is reported. The growth process was based oil the Au-catalyzed vapor-liquid-solid mechanism. These nanowires grow along the [100] axis; they are perpendicular to the substrate, have tapered shapes, and have diameters of about 90 rim at the base and 60 run at the top. High resolution transmission electron microscopy pictures reveal that the PbTe nanowires have a rock-salt structure and, in contrast to the one-dimensional structures of III-V and II-VI compound semiconductors such as GaAs. InAs, or ZnTe, are free from stacking faults. A theoretical analysis of these experimental findings, which is based oil ab initio modeling of the PbTe nanowires, is also presented.
  •  
15.
  • Gareev, R. R., et al. (författare)
  • Giant anisotropic magnetoresistance in insulating ultrathin (Ga,Mn)As
  • 2010
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Molecular-beam epitaxy grown, 5 nm thick annealed Ga0.95Mn0.05As films demonstrate transition from metallic to insulating state for sheet resistances near resistance quantum, which we connect with the two-dimensional hole localization. Below the metal-insulator transition we found the giant anisotropic magnetoresistance (GAMR) effect, which depends on the orientation of magnetization to crystallographic axes and demonstrates the twofold symmetry angular dependence. The GAMR manifests itself in positive magnetoresistance near 50% at T=1.7 K for H//[110] crystallographic direction in contrast to smaller negative magnetoresistance for H//[110] direction. We connect the GAMR with formation of high- and low-resistance states with different localization due to anisotropic spin-orbit interaction.
  •  
16.
  • Gas, Katarzyna, et al. (författare)
  • Structural and optical properties of self-catalytic GaAs:Mn nanowires grown by molecular beam epitaxy on silicon substrates
  • 2013
  • Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 5:16, s. 7410-7418
  • Tidskriftsartikel (refereegranskat)abstract
    • Mn-doped GaAs nanowires were grown in the self-catalytic growth mode on the oxidized Si(100) surface by molecular beam epitaxy and characterized by scanning and transmission electron microscopy, Raman scattering, photoluminescence, cathodoluminescence, and electron transport measurements. The transmission electron microscopy studies evidenced the substantial accumulation of Mn inside the catalyzing Ga droplets on the top of the nanowires. Optical and transport measurements revealed that the limit of the Mn content for self-catalysed growth of GaAs nanowires corresponds to the doping level, i.e., it is much lower than the Mn/Ga flux ratio (about 3%) used during the MBE growth. The resistivity measurements of individual nanowires confirmed that they are conductive, in accordance with the photoluminescence measurements which showed the presence of Mn2+ acceptors located at Ga sites of the GaAs host lattice of the nanowires. An anomalous temperature dependence of the photoluminescence related to excitons was demonstrated for Mn-doped GaAs nanowires.
  •  
17.
  • Gluba, L., et al. (författare)
  • On the nature of the Mn-related states in the band structure of (Ga,Mn)As alloys via probing the E-1 and E-1 + Delta(1) optical transitions
  • 2014
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The dilute (Ga,Mn)As became a model ferromagnetic semiconductor, however there is still a disagreement on the source of its magnetism. In this paper, we verify the ellipsometric results and compare them with more precise photoreflectance method, which gives an important insight into the interaction of the Mn-related states with the ones of GaAs valence band. No spectral shifts observed for the E-1 and E-1 + Delta(1) interband transitions in highly doped and annealed (Ga,Mn)As epitaxial layers indicate that the coupling between a detached Mn impurity band and the valence band does not occur. Our findings are supported by the characterizations of the (Ga,Mn)As epitaxial layers with the high resolution transmission electron microscopy and magnetization measurements. (c) 2014 AIP Publishing LLC.
  •  
18.
  • Gryglas-Borysiewicz, M., et al. (författare)
  • Hydrostatic pressure study of the paramagnetic-ferromagnetic phase transition in (Ga,Mn)As
  • 2010
  • Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 82:15
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of hydrostatic pressure on the paramagnetic-ferromagnetic phase transition has been studied in (Ga,Mn)As. The variation in the Curie temperature (T-C) with pressure was monitored by two transport methods: (1) measurement of zero-field resistivity versus temperature rho(T) and (2) dependence on temperature of the Hall voltage hysteresis loop. Two specimens of different resistivity characteristics were examined. The measured pressure-induced changes in T-C were relatively small (on the order of 1 K/GPa) for both samples, however they were opposite for the two.
  •  
19.
  • Gutowski, M. W., et al. (författare)
  • Interval Identification of FMR Parameters for Spin Reorientation Transition in (Ga,Mn)As
  • 2012
  • Ingår i: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 121:5-6, s. 1228-1230
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we report results of ferromagnetic resonance studies of a 6% 15 nm (Ga,Mn)As layer, deposited on (001)-oriented GaAs. The measurements were performed with in-plane oriented magnetic field, in the temperature range between 5 K and 120 K. We observe a temperature induced reorientation of the effective in-plane easy axis from [(1) over bar 10] to [110] direction close to the Curie temperature. The behavior of magnetization is described by anisotropy fields, H-eff (= 4 pi M - H-2 perpendicular to), H-2 parallel to, and H-4 parallel to. In order to precisely investigate this reorientation, numerical values of anisotropy fields have been determined using powerful - but still largely unknown - interval calculations. In simulation mode this approach makes possible to find all the resonance fields for arbitrarily oriented sample, which is generally intractable analytically. In "fitting" mode we effectively utilize full experimental information, not only those measurements performed in special, distinguished directions, to reliably estimate the values of important physical parameters as well as their uncertainties and correlations.
  •  
20.
  • Guziewicz, E., et al. (författare)
  • Synchrotron photoemission study of (Zn,Co)O films with uniform Co distribution
  • 2011
  • Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 80:10, s. 1046-1050
  • Konferensbidrag (refereegranskat)abstract
    • We present results of a resonant photoemission study of (Zn,Co)O films with Co content between 2% and 7%. The films were grown by Atomic Layer Deposition (ALD) at low temperature of 160 degrees C and show fully paramagnetic behavior. The Co ions are uniformly distributed in the ZnO matrix and are free of foreign phases and metal accumulations as indicated by TEM data. The electronic structure of (Zn,Co)O films was studied by Resonant Photoemission Spectroscopy across the Co3p-Co3d photoionization threshold. We have observed that the resonant enhancement of the photoemission intensity from the Co3d shell is not the same for samples with different cobalt content. We suggest that the Co3d contribution to the valence band depends on both Co and H content. (C) 2011 Elsevier Ltd. All rights reserved.
  •  
21.
  • Juszynski, P., et al. (författare)
  • Influence of Epitaxial Strain on Magnetic Anisotropy in (Ga,Mn)As
  • 2012
  • Ingår i: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 122:6, s. 1004-1006
  • Tidskriftsartikel (refereegranskat)abstract
    • Two (Ga,Mn)As samples having different magnetic anisotropy (one with in-plane easy axis and another one with out-of-plane easy axis) were studied by means of magnetotransport experiments. Anisotropy field B-A was determined for both samples as a function of temperature. For the sample having in-plane easy axis, an inversion of the direction of planar Hall effect hysteresis was observed upon increase of temperature. This result was simulated using the Stoner-Wohlfarth model.
  •  
22.
  • Juszynski, Piotr, et al. (författare)
  • Study of influence of domain structure on observed magnetoresistance anomalies in GaMnAs
  • 2013
  • Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 113:9, s. 4-093708
  • Tidskriftsartikel (refereegranskat)abstract
    • Magneto-transport properties of a Ga0.93Mn0.07As ferromagnetic semiconductor film with strong epitaxial strain (Ga0.7In0.3As buffer) have been studied. The observed magnetoresistance showed peculiar peaks at the magnetic fields corresponding to magnetization switching probed by Hall voltage. Computer simulations showed that these anomalies could originate from the formation of complex, island-like magnetic domains, and their propagation in the sample.
  •  
23.
  • Kamara, S., et al. (författare)
  • In-Plane Magnetic Anisotropy and Temperature Dependence of Switching Field in (Ga, Mn)As Ferromagnetic Semiconductors
  • 2012
  • Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 12:6, s. 4868-4873
  • Tidskriftsartikel (refereegranskat)abstract
    • We explore the magnetic anisotropy of GaMnAs ferromagnetic semiconductor by Planar Hall Effect (PHE) measurements. Using low magnitude of applied magnetic field (i.e., when the magnitude H is smaller than both cubic Hc and uniaxial Hu anisotropy field), we have observed various shapes of applied magnetic field direction dependence of Planar Hall Resistance (PHR). In particular, in two regions of temperature. At T TC/2 the “zigzag-shape” signal of PHR. They reflect different magnetic anisotropy and provide information about magnetization reversal process in GaMnAs ferromagnetic semiconductor. The theoretical model calculation of PHR based on the free energy density reproduces well the experimental data. We report also the temperature dependence of anisotropy constants and magnetization orientations. The transition of easy axis from biaxial to uniaxiale axes has been observed and confirmed by SQUID measurements.
  •  
24.
  • Kovacs, Andras, et al. (författare)
  • Effect of post-growth annealing on secondary phase formation in low-temperature-grown Mndoped GaAs
  • 2013
  • Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 46:14, s. 7-145309
  • Tidskriftsartikel (refereegranskat)abstract
    • The microstructures of annealed GaAs layers containing 0.1%, 0.5% and 2% Mn are studied using aberration-corrected transmission electron microscopy (TEM). The layers were grown by molecular beam epitaxy at 270 ◦C. After heat treatment at 400, 560 and 630 ◦C, they are found to contain precipitate complexes of cubic or hexagonal (Mn, Ga) As, orthorhombic or rhombohedral As and voids. Information about the crystallographic structures and compositions of the phases is obtained using high-resolution TEM, scanning TEM and energy-dispersive x-ray spectroscopy. A phase diagram for secondary phase formation in annealed GaMnAs layers doped with low Mn concentrations is proposed.
  •  
25.
  • Kovacs, A., et al. (författare)
  • Voids and Mn-rich inclusions in a (Ga,Mn)As ferromagnetic semiconductor investigated by transmission electron microscopy
  • 2011
  • Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 109:8, s. 1-083546
  • Tidskriftsartikel (refereegranskat)abstract
    • Voids adjacent to cubic (ZnS-type) and hexagonal (NiAs-type) Mn-rich nanocrystals are characterized using aberration-corrected transmission electron microscopy in an annealed Ga(0.995)Mn(0.005)As magnetic semiconductor specimen grown by molecular beam epitaxy. Nanobeam electron diffraction measurements suggest that the nanocrystals exhibit deviations in lattice parameter as compared to bulk MnAs. After annealing at 903 K, the magnetic transition temperature of the specimen is likely to be dominated by the presence of cubic ferromagnetic nanocrystals. In situ annealing inside the electron microscope is used to study the nucleation, coalescence, and grain growth of individual nanocrystals.
  •  
26.
  • Lang, J. J. K., et al. (författare)
  • Tin-stabilized (1 x 2) and (1 x 4) reconstructions on GaAs(100) and InAs(100) studied by scanning tunneling microscopy, photoelectron spectroscopy, and ab initio calculations
  • 2011
  • Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 605:9-10, s. 883-888
  • Tidskriftsartikel (refereegranskat)abstract
    • Tin (Sn) induced (1 x 2) reconstructions on GaAs(100) and InAs(100) substrates have been studied by low energy electron diffraction (LEED), photoelectron spectroscopy, scanning tunneling microscopy/spectroscopy (STM/STS) and ab initio calculations. The comparison of measured and calculated STM images and surface core-level shifts shows that these surfaces can be well described with the energetically stable building blocks that consist of Sn-III dimers. Furthermore, a new Sn-induced (1 x 4) reconstruction was found. In this reconstruction the occupied dangling bonds are closer to each other than in the more symmetric (1 x 2) reconstruction, and it is shown that the (1 x 4) reconstruction is stabilized as the adatom size increases.
  •  
27.
  • Laukkanen, P., et al. (författare)
  • Bismuth-containing c(4 x 4) surface structure of the GaAs(100) studied by synchrotron-radiation photoelectron spectroscopy and ab initio calculations
  • 2014
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 193, s. 34-38
  • Tidskriftsartikel (refereegranskat)abstract
    • Bismuth (Bi) induced c(4 x 4) surface structure of the GaAs(1 0 0) substrate, i.e., the GaAs(1 0 0)c(4 x 4)-Bi surface has been studied with synchrotron-radiation photoelectron spectroscopy and ab initio calculations. The surface was prepared by combining molecular beam epitaxy and in situ electron diffraction methods, and then the sample was transferred to a photoemission chamber without breaking ultrahigh vacuum conditions. Calculations show that the c(4 x 4)13 type unit cells, which consist of Bi-Bi and Bi-As dimers, are energetically favored on the surface and that Bi atoms occupy only the topmost atomic sites bonding to the As layer below. The presence of the c(4 x 4)(3 structure is supported by the comparison of measured and calculated core-level shifts of the GaAs(1 00)c(4 x 4)-Bi surface. Simulated scanning-tunneling-microscopy (STM) images, based on the suggested models, are presented for the comparison with future STM measurements. (C) 2014 Elsevier B.V. All rights reserved.
  •  
28.
  • Laukkanen, P., et al. (författare)
  • Bismuth-stabilized c(2X6) reconstruction on a InSb(100) substrate : Violation of the electron counting model
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 81:3
  • Tidskriftsartikel (refereegranskat)abstract
    • By means of scanning tunneling microscopy/spectroscopy (STM/STS), photoelectron spectroscopy, and first-principles calculations, we have studied the bismuth (Bi) adsorbate-stabilized InSb(100) substrate surface which shows a c(2X6) low-energy electron diffraction pattern [thus labeled Bi/InSb(100)c(2X6) surface] and which includes areas with metallic STS curves as well as areas with semiconducting STS curves. The first-principles phase diagram of the Bi/InSb(100) surface demonstrates the presence of the Bi-stabilized metallic c(2X6) reconstruction and semiconducting (4X3) reconstruction depending on the chemical potentials, in good agreement with STS results. The existence of the metallic c(2X6) phase, which does not obey the electron counting model, is attributed to the partial prohibition of the relaxation in the direction perpendicular to dimer rows in the competing reconstructions and the peculiar stability of the Bi-stabilized dimer rows. Based on (i) first-principles phase diagram, (ii) STS results, and (iii) comparison of the measured and calculated STM and photoemission data, we show that the measured Bi/InSb(100)c(2X6) surface includes metallic areas with the stable c(2X6) atomic structure and semiconducting areas with the stable (4X3) atomic structure.
  •  
29.
  • Laukkanen, P., et al. (författare)
  • Core-level shifts of the c(8 x 2)-reconstructed InAs(100) and InSb(100) surfaces
  • 2010
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 177:1, s. 52-57
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied In-stabilized c(8 2)-reconstructed InAs(1 0 0) and InSb(1 0 0) semiconductor surfaces, which play a key role in growing improved III-V interfaces for electronics devices, by core-level photoelectron spectroscopy and first-principles calculations. The calculated surface core-level shifts (SCLSs) for the zeta and zeta a models, which have been previously established to describe the atomic structures of the III-V(1 00)c(8 x 2) surfaces, yield hitherto not reported interpretation for the As 3d, In 4d, and Sb 4d core-level spectra of the III-V(1 00)c(8 x 2) surfaces, concerning the number and origins of SCLSs. The fitting analysis of the measured spectra with the calculated zeta and zeta a SCLS values shows that the InSb spectra are reproduced by the zeta SCLSs better than by the zeta a SCLSs. Interestingly, the zeta a fits agree better with the InAs spectra than the zeta fits do, indicating that the zeta a model describes the InAs surface better than the InSb surface. These results are in agreement with previous X-ray diffraction data. Furthermore, an introduction of the complete-screening model, which includes both the initial and final state effects, does not improve the fitting of the InSb spectra, proposing the suitability of the initial-state model for the SCLSs of the III-V(1 0 0)c(8 x 2) surfaces. The found SCLSs are discussed with the ab initio on-site charges.
  •  
30.
  • Laukkanen, Pekka, et al. (författare)
  • Surface Studies by Low-Energy Electron Diffraction and Reflection High-Energy-Electron Diffraction
  • 2012
  • Ingår i: Springer Series in Materials Science. ; 150, s. 1-21
  • Bokkapitel (refereegranskat)abstract
    • In this chapter, we present the basic concepts of the low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED) experiments. The main goal is to provide an overview of the exploitation of these instrumental methods for analyzing the surfaces of technologically important III–V compound semiconductors. In particular, the interpretation of LEED and RHEED patterns is discussed for the most representative reconstructions of GaAs(100), GaInAsN(100), and Bi-stabilized III–V(100) surfaces. Other application examples concern the use of RHEED for optimizing the growth conditions and growth rates used in molecular beam epitaxy of III–V device heterostructures.
  •  
31.
  • Lawniczak-Jablonska, Krystyna, et al. (författare)
  • Magnetic properties of MnSb inclusions formed in GaSb matrix directly during molecular beam epitaxial growth
  • 2011
  • Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 109:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Despite of intensive search for the proper semiconductor base materials for spintronic devices working at room temperature no appropriate material based on ferromagnetic semiconductors has been found so far. We demonstrate that the phase segregated system with MnSb hexagonal inclusions inside the GaSb matrix, formed directly during the molecular beam epitaxial growth reveals the ferromagnetic properties at room temperature and is a good candidate for exploitation in spintronics. Furthermore, the MnSb inclusions with only one crystalline structure were identified in this GaMn:MnSb granular material. The SQUID magnetometry confirmed that this material exhibits ferromagnetic like behavior starting from helium up to room temperature. Moreover, the magnetic anisotropy was found which was present also at room temperature, and it was proved that by choosing a proper substrate it is possible to control the direction of easy axis of inclusions' magnetization moment between in-plane and out-of-plane; the latter is important in view of potential applications in spintronic devices. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562171]
  •  
32.
  • Lawniczak-Jablonska, K., et al. (författare)
  • Structural and magnetic properties of GaAs:(Mn,Ga)As granular layers
  • 2011
  • Ingår i: Physica Status Solidi. B: Basic Research. - : Wiley. - 0370-1972. ; 248:7, s. 1609-1614
  • Tidskriftsartikel (refereegranskat)abstract
    • Granular GaAs:(Mn,Ga)As films were prepared by annealing the Ga0.92Mn0.08As/GaAs layer grown by the MBE method at low temperature. The annealing was performed at 500 or 600 degrees C. It is commonly accepted that this processing should result in formation of cubic zinc blende or hexagonal MnAs inclusions depending on the temperature. We demonstrate that such a priory assumption is not justified. The kind of formed inclusions depends not only on the annealing temperature but also on the number of defects and Mn atoms in the substitutional and interstitial positions in as grown sample. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  •  
33.
  • Lawniczak-Jablonska, K., et al. (författare)
  • Structural and magnetic properties of nanoclusters in GaMnAs granular layers
  • 2011
  • Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596. ; 184:6, s. 1530-1539
  • Tidskriftsartikel (refereegranskat)abstract
    • Structural and magnetic properties of GaAs thin films with embedded nanoclusters were investigated as a function of the annealing temperature and Mn content. Surprisingly, the presence of two kinds of nanoclusters with different structure was detected in most of the samples independently of the thermal processing or Mn content. This proved that the presence of a given type of clusters cannot be assumed a priori as is reported in many papers. The fraction of Mn atoms in each kind of cluster was estimated from the extended X-ray absorption fine structure analysis. This analysis ruled out the possibility of the existence of nanoclusters containing a hypothetic MnAs cubic compound-only (Ga,Mn)As cubic and hexagonal MnAs clusters were detected. Moreover the bimodal distribution of Mn magnetic moments was found, which scales with the estimated fraction of Mn atoms in the cubic and hexagonal clusters. (C) 2011 Elsevier Inc. All rights reserved.
  •  
34.
  • Lawniczak-Jablonska, K., et al. (författare)
  • The source of room temperature ferromagnetism in granular GaMnAs layers with zinc blende clusters
  • 2011
  • Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley. - 1862-6254. ; 5:2, s. 62-64
  • Tidskriftsartikel (refereegranskat)abstract
    • Granular GaAs:(Mn,Ga) As films were prepared by annealing the Ga0.985Mn0.015As/GaAs layers at 500 degrees C or 600 degrees C. It is commonly accepted that this processing should result in the formation of cubic or hexagonal MnAs clusters, respectively. We demonstrate that such a priori assumption is not justified. If in the as grown sample there are not many defects with the interstitial Mn atoms, only small cubic clusters can be formed even after annealing at 600 degrees C. Moreover, in a sample containing solely cubic GaMnAs clusters, the Mn ions are ferro-magnetically coupled at room temperature. This fact was explained by the existence of GaMnAs solid solution in the clusters, with content of Mn close to 20% (higher than ever found in the layers) as was confirmed by experiment and theory. Extended X-ray absorption spectroscopy studies excluded the possibility of formation of the hypothetic zinc blende MnAs clusters. Not more than one Mn atom was detected in the second shell around central Mn atom. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  •  
35.
  • Levchenko, K., et al. (författare)
  • Magnetic and Magneto-Transport Characterization of (Ga,Mn)(Bi,As) Epitaxial Layers
  • 2014
  • Ingår i: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 126:5, s. 1121-1124
  • Tidskriftsartikel (refereegranskat)abstract
    • High-quality layers of the (Ga,Mn)(Bi,As) quaternary compound semiconductor have been grown by the low-temperature molecular-beam epitaxy technique. An effect of Si incorporation into the (Ga,Mn)As ferromagnetic semiconductor and the post-growth annealing treatment of the layers have been investigated through examination of their magnetic and magneto-transport properties. Significant enhancement of the planar Hall effect magnitude upon addition of Si into the layers is interpreted as a result of increased spin orbit coupling in the (Ga,Mn)(Bi,As) layers.
  •  
36.
  • Proselkov, O., et al. (författare)
  • Thickness dependent magnetic properties of (Ga,Mn) As ultrathin films
  • 2012
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:26
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a monotonic reduction of Curie temperature in dilute ferromagnetic semiconductor (Ga,Mn) As upon a well controlled chemical-etching/oxidizing thinning from 15 nm down to complete removal of the ferromagnetic response. The effect already starts at the very beginning of the thinning process and is accompanied by the spin reorientation transition of the in-plane uniaxial anisotropy. We postulate that a negative gradient along the growth direction of self-compensating defects (Mn interstitial) and the presence of surface donor traps gives quantitative account on these effects within the p-d mean field Zener model with adequate modifications to take a nonuniform distribution of holes and Mn cations into account. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731202]
  •  
37.
  • Punkkinen, Marko Patrick John, et al. (författare)
  • Oxidized In-containing III-V(100) surfaces : Formation of crystalline oxide films and semiconductor-oxide interfaces
  • 2011
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:19, s. 195329-
  • Tidskriftsartikel (refereegranskat)abstract
    • Previously found oxidized III-V semiconductor surfaces have been generally structurally disordered and useless for applications. We disclose a family of well-ordered oxidized InAs, InGaAs, InP, and InSb surfaces found by experiments. The found epitaxial oxide-III-V interface is insulating and free of defects related to the harmful Fermi-level pinning, which opens up new possibilities to develop long-sought III-V metal-oxide-semiconductor transistors. Calculations reveal that the early stages in the oxidation process include only O-III bonds due to the geometry of the III-V(100)c(8 x 2) substrate, which is responsible for the formation of the ordered interface. The found surfaces provide a different platform to study the oxidation and properties of oxides, e. g., the origins of the photoemission shifts and electronic structures, using surface science methods.
  •  
38.
  • Romanowski, P., et al. (författare)
  • Defect Structure of High-Temperature-Grown GaMnSb/GaSb
  • 2010
  • Ingår i: Acta Physica Polonica A. - 0587-4246. ; 117:2, s. 341-343
  • Konferensbidrag (refereegranskat)abstract
    • GaMnSb/GaSb(100) layers with embedded MnSb inclusions have been grown at 720 K using MBE technique. This paper presents the investigation of the defect structure of Ga1-xMnxSb layers with different content of manganese (up to x = 0.07). X-ray diffraction method using conventional and synchrotron radiation was applied. Dimensions and shapes of inclusions were detected by scanning electron microscopy. Depth profiles of elements were measured using secondary ion mass spectroscopy technique.
  •  
39.
  • Sadowski, Janusz, et al. (författare)
  • Formation of two-dimensionally confined superparamagnetic (Mn, Ga)As nanocrystals in high-temperature annealed (Ga, Mn)As/GaAs superlattices
  • 2013
  • Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 25:19, s. 6-196005
  • Tidskriftsartikel (refereegranskat)abstract
    • The annealing-induced formation of (Mn, Ga)As nanocrystals in (Ga, Mn)As/GaAs superlattices was studied by x-ray diffraction, transmission electron microscopy and magnetometry. The superlattice structures with 50 Å thick (Ga, Mn)As layers separated by 25, 50 and 100 Å thick GaAs spacers were grown by molecular beam epitaxy at low temperature (250 ° C), and then annealed at high temperatures of 400, 560 and 630 ° C. The high-temperature annealing causes decomposition to a (Ga, Mn)As ternary alloy and the formation of (Mn, Ga)As nanocrystals inside the GaAs matrix. The nanocrystals are confined in the planes that were formerly occupied by (Ga, Mn)As layers for the up to 560 ° C annealing and diffuse throughout the GaAs spacer layers at 630 ° C annealing. The two-dimensionally confined nanocrystals exhibit a superparamagnetic behavior which becomes high-temperature ferromagnetism (~350 K) upon diffusion.
  •  
40.
  • Sadowski, Janusz, et al. (författare)
  • Formation process and superparamagnetic properties of (Mn,Ga)As nanocrystals in GaAs fabricated by annealing of (Ga,Mn)As layers with low Mn content
  • 2011
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:24, s. 245306-
  • Tidskriftsartikel (refereegranskat)abstract
    • X-ray diffraction, transmission electron microscopy, and magnetization measurements are employed to study the structural and magnetic properties of Mn-rich (Mn,Ga)As nanocrystals embedded in GaAs. These nanocomposites are obtained by moderate-temperature (400 degrees C) and high-temperature (560 degrees C and 630 degrees C) annealing of (Ga,Mn)As layers with Mn concentrations between 0.1% and 2%, grown by molecular beam epitaxy at 270 degrees C. Decomposition of (Ga,Mn)As is already observed at the lowest annealing temperature of 400 degrees C for layers with initial Mn content of 1% and 2%. Both cubic and hexagonal (Mn, Ga) As nanocrystals, with similar diameters of 7-10 nm, are observed to coexist in layers with an initial Mn content of 0.5% and 2% after higher-temperature annealing. Measurements of magnetization relaxation in the time span 0.1-10 000 s provide evidence for superparamagnetic properties of the (Mn,Ga)As nanocrystals, as well as for the absence of spin-glass dynamics. These findings point to weak coupling between nanocrystals even in layers with the highest nanocrystal density.
  •  
41.
  • Sadowski, Janusz, et al. (författare)
  • GaAs-MnAs nanowires
  • 2011
  • Ingår i: Physica Status Solidi. B: Basic Research. - : Wiley. - 0370-1972. ; 248:7, s. 1576-1580
  • Tidskriftsartikel (refereegranskat)abstract
    • Different strategies for obtaining nanowires (NWs) with ferromagnetic properties using the molecular beam epitaxy (MBE) grown nanostructures combining GaAs and Mn were investigated. Four types of structures have been studied: (i) self-catalyzed GaAs: Mn NWs grown at low temperatures on GaAs(100) substrates; (ii) GaAs: Mn NWs grown at high temperatures on Si(100) substrates; (iii) GaAs-GaMnAs core-shell NW structures; (iv) GaAs-MnAs core-shell NW structures grown on Si(100). Structures of types (i), (iii), and (iv) exhibit ferromagnetic properties. Right: Scanning electron microscopy image of Mn doped GaAs NWs with Ga droplets at the tops, grown by MBE on oxidized Si(100) substrate in the autocatalytic growth mode. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  •  
42.
  •  
43.
  • Schlapps, Markus, et al. (författare)
  • Coulomb blockade transport across lateral (Ga,Mn)As nanoconstrictions
  • 2010
  • Ingår i: Physica E-Low-Dimensional Systems & Nanostructures. - : Elsevier BV. - 1386-9477. ; 42:10, s. 2676-2680
  • Konferensbidrag (refereegranskat)abstract
    • We report on magnetotransport measurements of nanoconstricted (Ga,Mn)As devices showing very large resistance changes that can be controlled by both an electric and a magnetic field. Based on the bias voltage and temperature dependent measurements down to the millikelvin range we compare the models currently used to describe transport through (Ga,Mn)As nanoconstrictions. We provide an explanation for the observed spin-valve like behavior during a magnetic field sweep by means of the magnetization configurations in the device. Furthermore, we prove that Coulomb blockade plays a decisive role for the transport mechanism and show that modeling the constriction as a granular metal describes the temperature and bias dependence of the conductance correctly and allows to estimate the number of participating islands located in the constriction. (C) 2010 Elsevier B.V. All rights reserved.
  •  
44.
  • Šiušys, Aloyzas, et al. (författare)
  • All wurtzite (In,Ga)As-(Ga,Mn)As core-shell nanowires
  • 2014
  • Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 14:8, s. 4263-4272
  • Tidskriftsartikel (refereegranskat)abstract
    • Structural and magnetic properties of (In,Ga)As-(Ga,Mn)As core−shell nanowires grown by molecular beam epitaxy on GaAs(111)B substrate with gold catalyst have been investigated. (In,Ga)As core nanowires were grown at high temperature (500 °C) whereas (Ga,Mn)As shells were deposited on the {11̅00} side facets of the cores at much lower temperature (220 °C). High-resolution transmission electron microscopy images and high spectral resolution Raman scattering data show that both the cores and the shells of the nanowires have wurtzite crystalline structure. Scanning and transmission electron microscopy observations show smooth (Ga,Mn)As shells containing 5% of Mn epitaxially deposited on (In,Ga)As cores containing about 10% of In without any misfit dislocations at the core−shell interface. With the In content in the (In,Ga)As cores larger than 5% the (In,Ga)As lattice parameter is higher than that of (Ga,Mn)As and the shell is in the tensile strain state. Elaborated magnetic studies indicate the presence of ferromagnetic coupling in (Ga,Mn)As shells at the temperatures in excess of 33 K. This coupling is maintained only in separated mesoscopic volumes resulting in an overall superparamagnetic behavior which gets blocked below ∼17 K.
  •  
45.
  • Ulfat, Intikhab, 1966, et al. (författare)
  • As3d core level studies of (GaMn)As annealed under As capping
  • 2010
  • Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 604:2, s. 125-128
  • Tidskriftsartikel (refereegranskat)abstract
    • The surface of a Ga(0.95)Mn(0.05)As layer subjected to low temperature annealing under As capping has been studied by core level photoemission with focus on As3d spectrum. By detailed comparison with the surface of pure GaAs subjected to the same surface treatment, the As spectral component of the reacted surface layer has been identified. The relative intensity of this component is consistent with the notion of an MnAs monolayer terminating the annealed (GaMn)As surface.
  •  
46.
  • Ulfat, Intikhab, 1966, et al. (författare)
  • Post-growth annealing of (Ga,Mn)As under Sb capping
  • 2012
  • Ingår i: Applied Mechanics and Materials. - 1660-9336. - 9783037855102 ; 243-246, s. 243-246
  • Konferensbidrag (refereegranskat)abstract
    • (Ga,Mn)As is a model diluted ferromagnet system in which the atomic spins of Mn ions are ferromagnetically arranged due to the exchange interaction with valence band holes. An important tecchnological concern regarding this system has been approaches that might result in reduction of the density of Mn interstitial and increase in the content of Mn in order to make the system practically feasible. To accomplish the objective we report the results of our recent synchrotron radiation based spectroscopic investigations concening annealing induced modification of as-grown (Ga,Mn)As layers covered with Sb capping.
  •  
47.
  • Wikberg, J Magnus, et al. (författare)
  • Magnetocrystalline anisotropy and uniaxiality of MnAs/GaAs(100) films
  • 2011
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:2, s. 024417-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an investigation of the magnetic behavior of epitaxial MnAs films grown on GaAs(100). We address the dependence of the magnetic moment, ferromagnetic transition temperature (Tc), and magnetocrystalline anisotropy constants on epitaxial conditions. From thorough structural and magnetic investigations, our findings indicate a more complex relationship between strain and magnetic properties in MnAs films than a simple stretch/compression of the unit cell axes. While a small increase is seen in the anisotropy constants, the enhancement of the magnetic moment at saturation is significant. Results of x-ray magnetic circular dichroism show a behavior of the spin and orbital moment that is consistent with a structural transition at Tc. In particular, we find that the ratio of the orbital to the spin moment shows a marked increase in the coexistence region of the ferromagnetic α- and paramagnetic β-phases a result that is well in accord with the observed increase in the c/a ratio in the same temperature region. The ab initio density functional calculations reveal that the magnetic properties are more sensitive towards change in the ab-plane compared to change in the c-axis which is explained by the analysis of band structures. The effects of electron correlation in MnAs using ab initio dynamical mean field theory are also presented.
  •  
48.
  • Wolska, A., et al. (författare)
  • MnSb inclusions in the GaSb matrix studied by X-ray absorption spectroscopy
  • 2011
  • Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 80:10, s. 1026-1030
  • Konferensbidrag (refereegranskat)abstract
    • The MBE processes were performed in order to form the MnSb inclusions. Two kinds of substrates (GaSb and GaAs) as well as growth temperatures (450 and 520 degrees C) were examined. SEM imaging was performed to determine the shape and size of formed inclusions. In all the samples the inclusions of few hundred nm were formed. Their shapes depended strongly on the type of substrate while the size slightly increases with the growth temperature. The X-ray absorption techniques were used to monitor the local structure around Mn atoms and confirmed that the neighborhood of Mn atoms in the layers was close to that of the MnSb reference powder. We succeed in the formation of the GaSb layers with Mn assembled only into MnSb inclusions on both types of substrates: GaAs(1 1 1)A and GaSb(1 00). However, in case of the GaAs(1 1 1)A substrates, the atomic order around Mn atoms in MnSb inclusions is less perfect than in case of the GaSb(1 0 0) substrates. (C) 2011 Elsevier Ltd. All rights reserved.
  •  
49.
  • Wosinski, Tadeusz, et al. (författare)
  • Domain-wall controlled (Ga,Mn)As nanostructures for spintronic applications
  • 2013
  • Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - : Elsevier BV. - 1386-9477. ; 51, s. 128-134
  • Tidskriftsartikel (refereegranskat)abstract
    • Valence-band structure and magnetic properties, especially magnetic anisotropies, in the (Ga,Mn)As diluted ferromagnetic semiconductor are shortly discussed. Next, magneto-resistive, cross-like nanostructures fabricated by electron-beam lithography patterning and chemical etching from thin (Ga,Mn)As epitaxial layers are described. The nanostructures, composed of two perpendicular nanostripes crossing in the middle of their length, represent four-terminal devices, in which an electric current can be driven through any of the two nanostripes. In these devices, which make use of the patterning-induced magnetic anisotropy, a novel magneto-resistive memory effect related to a rearrangement of magnetic domain walls in the central part of the device, has been demonstrated. The effect consists in that the zerb-field resistance of a nanostripe depends on the direction of previously applied magnetic field. The nanostructures can thus work as two-state devices providing basic elements of nonvolatile memory cells. (C) 2012 Elsevier B.V. All rights reserved.
  •  
50.
  • Wosinski, T., et al. (författare)
  • Memory Behavior of the Planar Hall Effect in Ferromagnetic (Ga, Mn)As/GaAs Superlattices
  • 2010
  • Ingår i: Journal of Superconductivity and Novel Magnetism. - : Springer Science and Business Media LLC. - 1557-1939 .- 1557-1947. ; 23:1, s. 83-86
  • Konferensbidrag (refereegranskat)abstract
    • The planar Hall effect (PHE) has been studied in short period (Ga, Mn)As/GaAs superlattices displaying a ferromagnetic interlayer coupling between the magnetic layers. Complex dependence of the PHE on applied magnetic field is explained by taking into account the magnetocrystalline anisotropy of the (Ga, Mn)As layers, which results from biaxial compressive strain in the layers epitaxially grown on GaAs. Two-state behavior of the planar Hall resistance at zero magnetic field provides its usefulness for applications in nonvolatile memory devices. In addition, using an appropriate sequence of applied magnetic fields four different states of the planar Hall resistance, suitable for quaternary memory devices, can be realized owing to the formation of a stable multidomain structure in the Hall bar.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-50 av 56

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy