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Levchenko, K., Prokscha, T., Sadowski, J., Radelytskyi, I., Jakiela, R., Trzyna, M., . . . Wosinski, T. (2019). Evidence for the homogeneous ferromagnetic phase in (Ga, Mn) (Bi, As) epitaxial layers from muon spin relaxation spectroscopy. Scientific Reports, 9, 1-8, Article ID 3394.
Open this publication in new window or tab >>Evidence for the homogeneous ferromagnetic phase in (Ga, Mn) (Bi, As) epitaxial layers from muon spin relaxation spectroscopy
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2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, p. 1-8, article id 3394Article in journal (Refereed) Published
Abstract [en]

Ferromagnetic semiconductor thin layers of the quaternary (Ga,Mn)(Bi,As) and reference, ternary (Ga, Mn) As compounds, epitaxially grown under either compressive or tensile strain, have been characterized from a perspective of structural and magnetization homogeneity. The quality and composition of the layers have been confirmed by secondary-ion mass spectrometry (SIMS). A thorough evaluation of the magnetic properties as a function of temperature and applied magnetic field has been performed by means of SQUID magnetometry and low-energy muon spin relaxation (mu SR) spectroscopy, which enables studying local (on the nanometer scale) magnetic properties of the layers. The results testify that the ferromagnetic order builds up almost homogeneously below the Curie temperature in the full volume fraction of both the (Ga, Mn) As and (Ga, Mn)(Bi, As) layers. Incorporation of a small amount of heavy Bi atoms into (Ga, Mn) As, which distinctly enhances the strength of spin-orbit coupling in the quaternary (Ga, Mn)(Bi, As) layers, does not deteriorate noticeably their magnetic properties.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Physics, Electrotechnology
Identifiers
urn:nbn:se:lnu:diva-81083 (URN)10.1038/s41598-019-40309-y (DOI)000460123600066 ()30833684 (PubMedID)2-s2.0-85062407093 (Scopus ID)
Available from: 2019-03-15 Created: 2019-03-15 Last updated: 2019-08-29Bibliographically approved
Gluba, L., Yastrubchak, O., Domagala, J. Z., Jakiela, R., Andrearczyk, T., Zuk, J., . . . Sawicki, M. (2018). Band structure evolution and the origin of magnetism in (Ga,Mn) As: From paramagnetic through superparamagnetic to ferromagnetic phase. Physical Review B, 97(11), Article ID 115201.
Open this publication in new window or tab >>Band structure evolution and the origin of magnetism in (Ga,Mn) As: From paramagnetic through superparamagnetic to ferromagnetic phase
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2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 11, article id 115201Article in journal (Refereed) Published
Abstract [en]

The high-spectral-resolution optical studies of the energy gap evolution, supplemented with electronic, magnetic, and structural characterization, show that the modification of the GaAs valence band caused by Mn incorporation occurs already for a very low Mn content, much lower than that required to support ferromagnetic spin-spin coupling in (Ga,Mn) As. Only for n-type (Ga,Mn) As with the Mn content below about 0.3% the Mn-related extended states are visible as a feature detached from the valence-band edge and partly occupied with electrons. The combined magnetic and low-temperature photoreflectance studies presented here indicate that the paramagnetic <-> ferromagnetic transformation in p-type (Ga,Mn) As takes place without imposing changes of the unitary character of the valence band with the Fermi level located therein. The whole process is rooted in the nanoscale fluctuations of the local (hole) density of states and the formation of a superparamagnetic-like state. The Fermi level in (Ga,Mn) As is coarsened by the carrier concentration of the itinerant valence band holes and further fine-tuned by the many-body interactions.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-72022 (URN)10.1103/PhysRevB.97.115201 (DOI)000427311200003 ()2-s2.0-85044001007 (Scopus ID)
Available from: 2018-03-29 Created: 2018-03-29 Last updated: 2019-08-29Bibliographically approved
Sawicki, M., Proselkov, O., Sliwa, C., Aleshkevych, P., Domagala, J. Z., Sadowski, J. & Dietl, T. (2018). Cubic anisotropy in (Ga,Mn) As layers: Experiment and theory. Physical Review B, 97(18), Article ID 184403.
Open this publication in new window or tab >>Cubic anisotropy in (Ga,Mn) As layers: Experiment and theory
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2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 18, article id 184403Article in journal (Refereed) Published
Abstract [en]

Historically, comprehensive studies of dilute ferromagnetic semiconductors, e.g., p-type (Cd,Mn) Te and (Ga,Mn) As, paved the way for a quantitative theoretical description of effects associated with spin-orbit interactions in solids, such as crystalline magnetic anisotropy. In particular, the theory was successful in explaining uniaxial magnetic anisotropies associated with biaxial strain and nonrandom formation of magnetic dimers in epitaxial (Ga,Mn) As layers. However, the situation appears much less settled in the case of the cubic term: the theory predicts switchings of the easy axis between in-plane < 100 > and < 110 > directions as a function of the hole concentration, whereas only the < 100 > orientation has been found experimentally. Here, we report on the observation of such switchings by magnetization and ferromagnetic resonance studies on a series of high-crystalline quality (Ga,Mn) As films. We describe our findings by themean-field p-d Zener model augmented with three new ingredients. The first one is a scattering broadening of the hole density of states, which reduces significantly the amplitude of the alternating carrier-induced contribution. This opens the way for the two other ingredients, namely the so-far disregarded single-ion magnetic anisotropy and disorder-driven nonuniformities of the carrier density, both favoring the < 100 > direction of the apparent easy axis. However, according to our results, when the disorder gets reduced, a switching to the < 110 > orientation is possible in a certain temperature and hole concentration range.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-76812 (URN)10.1103/PhysRevB.97.184403 (DOI)000431989000003 ()2-s2.0-85047133231 (Scopus ID)
Available from: 2018-07-11 Created: 2018-07-11 Last updated: 2019-08-29Bibliographically approved
Sadowski, J., Dziawa, P., Kaleta, A., Kurowska, B., Reszka, A., Story, T. & Kret, S. (2018). Defect-free SnTe topological crystalline insulator nanowires grown by molecular beam epitaxy on graphene. Nanoscale, 10(44), 20772-20778
Open this publication in new window or tab >>Defect-free SnTe topological crystalline insulator nanowires grown by molecular beam epitaxy on graphene
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2018 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, no 44, p. 20772-20778Article in journal (Refereed) Published
Abstract [en]

SnTe topological crystalline insulator nanowires have been grown by molecular beam epitaxy on graphene/SiC substrates. The nanowires have a cubic rock-salt structure, they grow along the [001] crystallographic direction and have four sidewalls consisting of {100} crystal planes known to host metallic surface states with a Dirac dispersion. Thorough high resolution transmission electron microscopy investigations show that the nanowires grow on graphene in the van der Waals epitaxy mode induced when the catalyzing Au nanoparticles mix with Sn delivered from a SnTe flux, providing a liquid Au-Sn alloy. The nanowires are totally free from structural defects, but their {001} sidewalls are prone to oxidation, which points out the necessity of depositing a protective capping layer in view of exploiting the magneto-electric transport phenomena involving charge carriers occupying topologically protected states.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Physical Sciences
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-79094 (URN)10.1039/c8nr06096g (DOI)000450442500026 ()30402641 (PubMedID)2-s2.0-85056639966 (Scopus ID)
Available from: 2018-12-06 Created: 2018-12-06 Last updated: 2019-08-29Bibliographically approved
Kwiatkowski, A., Gryglas-Borysiewicz, M., Juszynski, P., Przybytek, J., Sawicki, M., Sadowski, J., . . . Baj, M. (2018). Galvanomagnetic methods of Curie temperature determination in (Ga,Mn)As. Journal of Magnetism and Magnetic Materials, 467, 120-128
Open this publication in new window or tab >>Galvanomagnetic methods of Curie temperature determination in (Ga,Mn)As
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2018 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 467, p. 120-128Article in journal (Refereed) Published
Abstract [en]

We critically discuss various experimental methods to determine Curie temperature T-C of (Ga,Mn)As thin layers or other conducing magnetic materials by means of electric charge transport measurements. They all base on the influence of sample magnetization on the magnetoresistivity tensor <(rho)overcap>and are an alternative to the method based upon an analysis of the temperature derivative of the sample resistance (Novak a al., 2008). These methods can be applied even when standard SQUID magnetometers are difficult or impossible to use - for example for extremely small samples or in the case of experiments performed at very specific physical conditions, e.g. at high hydrostatic pressure inside the clamp cell. We show that the use of the so called Arrott plot prepared with the use of high magnetic field isotherms rho(xx)(H-0), rho(x)y(H-0) (H-0 - external magnetic field) may lead to substantial (of the order of 10 K) divergence of the obtained T-c values depending on the assumptions which are necessary to make in this case and depending on the direction of a magnetic anisotropy easy axis. We also propose a number of ways how to obtain, basing on low magnetic field isotherms rho(xx)(H-0), rho(xy)(H-0) clear and characteristic features which are closely related to the ferromagnetic-paramagnetic phase transition.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Curie-temperature, Ferromagnetic semiconductors, (Ga, Mn)As
National Category
Physical Sciences
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-77486 (URN)10.1016/j.jmmm.2018.07.049 (DOI)000441872500017 ()2-s2.0-85050450667 (Scopus ID)
Available from: 2018-08-31 Created: 2018-08-31 Last updated: 2019-08-29Bibliographically approved
Kret, S., Kaleta, A., Bilska, M., Kurowska, B., Siusys, A., Dabrowski, J. & Sadowski, J. (2017). FIB Method of Sectioning of III-V Core-Multi-Shell Nanowires for Analysis of Core/Sell Interfaces by High Resolution TEM. Paper presented at 12th Symposium of Magnetic Measurements and Modeling (SMMM), OCT 17-19, 2016, Siewierz, POLAND. Acta Physica Polonica. A, 131(5), 1332-1335
Open this publication in new window or tab >>FIB Method of Sectioning of III-V Core-Multi-Shell Nanowires for Analysis of Core/Sell Interfaces by High Resolution TEM
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2017 (English)In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 131, no 5, p. 1332-1335Article in journal (Refereed) Published
Abstract [en]

The core-multishell wurtzite structure (In, Ga) As-(Ga, Al) As-(Ga, Mn) As semiconductor nanowires have been successfully grown on GaAs(111) B substrates using MBE technique. The nanowires cores were grown with gold eutectic catalyser in vapour-liquid-solid growth mode. The double shell overgrowth, on the side facets of nanowires, was performed using lower substrate temperature (about 400 degrees C, and 230 degrees C, for (Ga, Al) As, and (Ga, Mn) As shell growth, respectively). The polytypic ordering, defects, chemistry and geometric perfection of the core and the shells have been analysed at atomic level by advanced transmission electron microscope techniques with the use of axial and longitudinal section of individual nanowires prepared by focused ion beam. High quality cross-sections suitable for quantitative transmission electron microscope analysis have been obtained and enabled analysis of interfaces between the core and the shells with near atomic resolution. All investigated shells are epitaxial without misfit dislocations at the interface. Some of the shells thicknesses are not symmetric, which is due to the shadowing effects of neighbouring nanowires and directional character of the elemental fluxes in the MBE growth process.

Place, publisher, year, edition, pages
Polish Physical Society, 2017
National Category
Physical Sciences
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-67503 (URN)10.12693/APhysPolA.131.1332 (DOI)000403507600033 ()
Conference
12th Symposium of Magnetic Measurements and Modeling (SMMM), OCT 17-19, 2016, Siewierz, POLAND
Available from: 2017-08-29 Created: 2017-08-29 Last updated: 2019-09-05Bibliographically approved
Gryglas-Borysiewicz, M., Juszynski, P., Kwiatkowski, A., Przybytek, J., Sadowski, J., Sawicki, M., . . . Wasik, D. (2017). Hydrostatic-pressure-induced changes of magnetic anisotropy in (Ga, Mn) As thin films. Journal of Physics: Condensed Matter, 29(11), Article ID 115805.
Open this publication in new window or tab >>Hydrostatic-pressure-induced changes of magnetic anisotropy in (Ga, Mn) As thin films
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2017 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 11, article id 115805Article in journal (Refereed) Published
Abstract [en]

The impact of hydrostatic pressure on magnetic anisotropy energies in (Ga, Mn) As thin films with in-plane and out-of-plane magnetic easy axes predefined by epitaxial strain was investigated. In both types of sample we observed a clear increase in both in-plane and out-of-plane anisotropy parameters with pressure. The out-of-plane anisotropy constant is well reproduced by the mean-field p-d Zener model; however, the changes in uniaxial anisotropy are much larger than expected in the Mn-Mn dimer scenario.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2017
Keywords
magnetic anisotropy, (Ga, Mn)As, thin films, hydrostatic pressure, spintronics
National Category
Condensed Matter Physics
Research subject
Physics, Condensed Matter Physics
Identifiers
urn:nbn:se:lnu:diva-64196 (URN)10.1088/1361-648X/aa546d (DOI)000395756600003 ()27991443 (PubMedID)2-s2.0-85013187994 (Scopus ID)
Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2019-08-29Bibliographically approved
Baranska, M., Dluzewski, P., Kret, S., Morawiec, K., Li, T. & Sadowski, J. (2017). Off-Axis Electron Holography of Magnetic Nanostructures: Magnetic Behavior of Mn Rich Nanoprecipitates in (Mn,Ga) As System. Paper presented at 12th Symposium of Magnetic Measurements and Modeling (SMMM), OCT 17-19, 2016, Siewierz, POLAND. Acta Physica Polonica. A, 131(5), 1406-1408
Open this publication in new window or tab >>Off-Axis Electron Holography of Magnetic Nanostructures: Magnetic Behavior of Mn Rich Nanoprecipitates in (Mn,Ga) As System
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2017 (English)In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 131, no 5, p. 1406-1408Article in journal (Refereed) Published
Abstract [en]

The Lorentz off-axis electron holography technique is applied to study the magnetic nature of Mn rich nanoprecipitates in (Mn,Ga) As system. The effectiveness of this technique is demonstrated in detection of the magnetic field even for small nanocrystals having an average size down to 20 nm.

Place, publisher, year, edition, pages
Polish Physical Society, 2017
National Category
Physical Sciences
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-67504 (URN)10.12693/APhysPolA.131.1406 (DOI)000403507600052 ()
Conference
12th Symposium of Magnetic Measurements and Modeling (SMMM), OCT 17-19, 2016, Siewierz, POLAND
Available from: 2017-08-30 Created: 2017-08-30 Last updated: 2019-09-05Bibliographically approved
Sadowski, J., Kret, S., Siusys, A., Wojciechowski, T., Gas, K., Islam, F., . . . Sawicki, M. (2017). Wurtzite (Ga,Mn)As nanowire shells with ferromagnetic properties. Nanoscale, 9(6), 2129-2137
Open this publication in new window or tab >>Wurtzite (Ga,Mn)As nanowire shells with ferromagnetic properties
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2017 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, no 6, p. 2129-2137Article in journal (Refereed) Published
Abstract [en]

(Ga,Mn)As having a wurtzite crystal structure was coherently grown by molecular beam epitaxy on the 1100 side facets of wurtzite (Ga,In)As nanowires and further encapsulated by (Ga,Al)As and low temperature GaAs. For the first time, a truly long-range ferromagnetic magnetic order is observed in non-planar (Ga,Mn)As, which is attributed to a more effective hole confinement in the shell containing Mn by the proper selection/choice of both the core and outer shell materials. © The Royal Society of Chemistry.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
Keywords
Crystal structure; Ferromagnetic materials; Ferromagnetism; Gallium; Molecular beam epitaxy; Nanowires; Temperature; Zinc sulfide, Ferromagnetic properties; Hole confinement; Low-temperature GaAs; Magnetic orders; Outer shells; Wurtzite crystal structure; Wurtzites, Manganese
National Category
Physical Sciences
Research subject
Natural Science, Physics
Identifiers
urn:nbn:se:lnu:diva-61167 (URN)10.1039/c6nr08070g (DOI)000395626600004 ()2-s2.0-85012111095 (Scopus ID)
Available from: 2017-03-08 Created: 2017-03-08 Last updated: 2019-09-06Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9495-2648

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