| 1. |
- Lawniczak-Jablonska, K., et al.
(författare)
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Structural and magnetic properties of GaAs:(Mn,Ga)As granular layers
- 2011
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Ingår i: Physica Status Solidi. B: Basic Research. - : Wiley. - 0370-1972. ; 248:7, s. 1609-1614
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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
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| 2. |
- Lawniczak-Jablonska, K., et al.
(författare)
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Structural and magnetic properties of nanoclusters in GaMnAs granular layers
- 2011
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Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596. ; 184:6, s. 1530-1539
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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.
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| 3. |
- Lawniczak-Jablonska, K., et al.
(författare)
-
The source of room temperature ferromagnetism in granular GaMnAs layers with zinc blende clusters
- 2011
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Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley. - 1862-6254. ; 5:2, s. 62-64
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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
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| 4. |
- Wolska, A., et al.
(författare)
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MnSb inclusions in the GaSb matrix studied by X-ray absorption spectroscopy
- 2011
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 80:10, s. 1026-1030
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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.
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| 5. |
- Wolska, A., et al.
(författare)
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Structural and magnetic properties of Mn(+) implanted silicon crystals studied using X-ray absorption spectroscopy techniques
- 2011
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 80:10, s. 1119-1124
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Tidskriftsartikel (refereegranskat)abstract
- The implantation of Mn ions into two Si substrates with different doping (P or B), resistivity and oxygen content was performed at low and high substrate temperatures. Different post-implantation processing was carried out to study its influence on the structural and magnetic properties of these samples. The local order around the Mn atoms was characterized by X-ray absorption fine structure techniques and the magnetic properties of the Mn ionic cores were determined by means of X-ray magnetic circular dichroism measurements. The results are discussed in relation to the structural and macroscopic magnetic properties. It is shown that the amorphous matrix speeds up the formation of MnSi(x) inclusions. However, the existence of inclusions or the type of electrically active dopants is not directly related to the magnetic properties. Therefore, in the performed studies, the importance of structural defects on the magnetic properties was confirmed. A localized magnetic moment carried by the Mn ionic cores could not be detected by means of dichroic measurements.
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| 6. |
- Wolska, A., et al.
(författare)
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Study of the Local Environment of Mn Ions Implanted in GaSb
- 2010
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Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 117:2, s. 286-292
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Tidskriftsartikel (refereegranskat)abstract
- The first attempts to establish an implantation process leading to formation of ferromagnetic inclusions inside the GaSb matrix are presented. Gallium antimonide containing ferromagnetic MnSb precipitations is considered as a promising material for novel spintronic applications. It is possible to obtain such inclusions during the molecular beam epitaxy (MBE) growth. However, for commercial application it would be also important to find an optimal way of producing this kind of inclusions by Mn ions implantation. In order to achieve this goal, several parameters of implantation and post annealing procedures were tested. The ion energy was kept at 10 keV or 150 keV and four different ion doses were applied, as well as various annealing conditions. The analysis of X-ray absorption spectra allowed to estimate the local atomic order around Mn atoms. Depending on the implantation energy and annealing processes, the manganese oxides or manganese atoms located in a heavily defected GaSb matrix were observed. The performed analysis helped in indicating the main obstacles in formation of MnSb inclusions inside the GaSb matrix by Mn ion implantation.
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| 7. |
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