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1
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Magnetism and Superconductivity in Nd_{0.81}Sr_{0.19}MnO_3/YBa_2Cu_3O_7 Superlattices

100%
Komissarov I., Przysłupski P., Dłużewski P., Sawicki M.
Acta Physica Polonica A
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2004
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vol. 105
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issue 1-2
127-132
EN
We report on the growth, structural and magnetic characterization of Nd_{0.81}Sr_{0.19}MnO_3/YBa_2Cu_3O_7 (NSMO/YBCO) superlattices. The NSMO system for the doping level of x=0.19 is a ferromagnetic insulator. Multilayers with a fixed NSMO thickness of 13 unit cells and a varying YBCO layer thickness from 2 unit cells to 6 unit cells were sputtered on LaAlO_3 substrates. An onset of superconducting transition is seen starting from the multilayer with 3 unit cells of YBCO layer thickness. Hysteresis loops recorded above and below the superconducting transition show a signature of interlayer exchange coupling.
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MnAs Nanocrystals Embedded in GaAs

76%
Kwiatkowski A., Wasik D., Kamińska M., Twardowski A., Dłużewski P., Borysiuk J., Sadowski J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1207-1211
EN
Magnetic properties of MnAs nanocrystals embedded in GaAs are analyzed in the frame of phenomenological model proposed by Sasaki for ferritin superparamagnets. Our calculations explain qualitatively experimental data of magnetization versus temperature, obtained according to zero-field-cooled and field-cooled protocols. They show dynamics of magnetization of MnAs nanocrystals in range of temperature from 10 K to 320 K. There is transition from state in which very slow dynamics is observed (frozen state) to state in which dynamics is fast (quasi-superparamagnetic state).
3
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Ultrathin Niobium in the Si/Nb/Si Trilayers

76%
Zaytseva I., Abal'oshev O., Dłużewski P., Minikayev R., Cieplak M., Zhu L., Chien C.
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vol. 126
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issue 4a
A-140-A-144
EN
We study magnetotransport properties of the Si/Nb/Si trilayers, in which the thickness of niobium, d, changes from 1.1 nm to 50 nm, while the thickness of Si is fixed at 10 nm. The niobium films are amorphous for d < 4 nm, while in thicker films the alligned polycrystalline grains are formed. We observe that the Hall coefficient changes sign into negative in the films with d < 1.6 nm. We also find that in the ultrathin films the magnetic field induces a transition from the superconducting into a metallic phase with the resistance smaller than the normal-state resistance.
4
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Off-Axis Electron Holography of Magnetic Nanostructures: Magnetic Behavior of Mn Rich Nanoprecipitates in (Mn,Ga)As System

76%
Barańska M., Dłużewski P., Kret S., Morawiec K., Li T., Sadowski J.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1406-1408
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.
5
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Native Deep-Level Defects in MBE-Grown p-Type CdTe

76%
Olender K., Wosiński T., Mąkosa A., Dłużewski P., Kolkovsky V., Karczewski G.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
946-949
EN
Deep-level transient spectroscopy was used to study the defect levels in p-type CdTe layers grown by the molecular-beam epitaxy technique on lattice-mismatched GaAs substrates. In our measurements we have observed five hole traps. Two of the traps, displaying exponential capture kinetics, have been assigned to native point defects, the Cd vacancy and a complex formed of Cd vacancy and Te antisite, produced in the CdTe layers during their growth. The other two traps have been attributed to electronic states of threading dislocations on the ground of their logarithmic capture kinetics. The last trap, which was observed only when the investigated space charge region was close to the metal-semiconductor interface, has been ascribed to surface states.
6
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Superconductivity and Magnetism in Nd_{0.5}Sr_{0.5}MnO_3/YBa_2Cu_3O_7 Superlattices

76%
Tsarou A., Paszkowicz W., Minikayev R., Dłużewski P., Sawicki M., Przysłupski P.
Acta Physica Polonica A
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2007
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vol. 111
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issue 1
179-183
EN
We report the synthesis and characterization of Nd_{0.5}Sr_{0.5}MnO_3/YBa_2Cu_3O_7 superlattices. X-ray diffraction studies show that the superlattices are [001] oriented. We observe that the magnetic ground state of Nd_{0.5}Sr_{0.5}MnO_3 system in a multilayered structure is strongly dependent on the substrate.
7
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Structural Properties of Co and CoFe Electrodes Forming a Magnetic Tunnel Junction

76%
Gładczuk L., Pankowski P., Paszkowicz W., Dłużewski P., Wójcik M., Przysłupski P.
Acta Physica Polonica A
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2007
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vol. 111
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issue 1
135-140
EN
The M_1/MgO/M_2 trilayer tunnel magnetoresistance systems are studied by means of X-ray diffraction, NMR, and transmission electron microscopy techniques. As M_1 and M_2 electrodes we used Co, Fe, and CoFe layers. The growth mechanism and structural quality of both electrodes and of the epitaxial MgO barrier forming the magnetic tunnel junctions are experimentally examined. It is shown that the crystallographic coherence of magnetic tunnel junctions across the MgO barrier is significantly disturbed by imperfect crystal structure of magnetic electrodes. The NMR results indicate a difference in short-range order between bottom and top electrodes.
8
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Application of Graphics Processing Unit for In-Line Electron Holography

76%
Morawiec K., Dłużewski P., Kret S., Szczepańska A., Li T., Sloan J.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1353-1356
EN
In the present work, software for exit electron wave reconstruction based on the iterative approach was implemented and a new method for drift-correction of the focal series was proposed.
9
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Synchrotron Photoemission Study of Ferromagnetic (Zn,Co)O Films

76%
Guziewicz E., Lukasiewicz M., Wachnicki L., Kopalko K., Dłużewski P., Jakiela R., Godlewski M.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-40-A-42
EN
The electronic structure of ferromagnetic (Zn,Co)O films was investigated by resonant photoemission across the Co 3p → Co 3d photoionization threshold, e.g. using photon energy between 50 eV and 66 eV. The films were grown by atomic layer deposition at temperature between 160C and 300C and they differed in distribution and content of cobalt. The maximum of the Fano resonance was observed at photon energy 63 eV, whereas the minimum at 58 eV. The difference between energy distribution curves taken at 63 eV and the one taken at 58 eV was calculated for a series of samples. It shows that the Co 3d contribution to the valence band electronic structure of ferromagnetic (Zn,Co)O films differs significantly from that of the films which show the paramagnetic response.
10
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Lattice Parameter Relaxation during MBE of ZnTe/Cd_{1-x}Zn_{x}Te/Cd_{0.5}Zn_{0.5}Te Buffer Layers by RHLED and HRTEM

64%
Kret S., Karczewski G., Zakrzewski A., Dłużewski P., Dubon A., Wojtowicz T., Kossut J., Delamarre C., Laval J. Y.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
795-798
EN
The dynamics of the lattice relaxation processes were investigated us­ing a reflection of a high energy electron diffraction analysis system dur­ing growth by molecular beam epitaxy of ZnTe/Cd_{1-x}Ζn_{x}Te/Cd_{0.5}Mn_{0.5}Te buffers on GaAs substrates. The variation of the lattice parameter recorded by the high energy electron diffraction during the growth was later confirmed by an analysis of high resolution transmission electron microscopy images. We report also on an observation of oscillations of the lattice parameter during the deposition of several first layers of ZnTe on CdTe.
11
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Electron Microscopy and X-ray Structural Investigations of Incommensurate Spin-Ladder Sr_{4.1}Ca_{4.7}Bi_{0.3}Cu_{17}O_{29} Single Crystals

64%
Dłużewski P., Pietraszko A., Kozłowski M., Szczepańska A., Górecka J., Baran M., Leonyuk L., Babonas G.-J., Lebedev O., Szymczak R.
Acta Physica Polonica A
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2000
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vol. 98
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issue 6
729-737
EN
Transmission electron microscopy and X-ray diffraction proved chain ladder incommensurate single crystal structure of investigated samples. The incommensurate ratio was determined from the X-ray and electron diffraction being equal to 0.704. Diffuse scattering intensities localised on the planes perpendicular to the c*-axis and passing through the spots originating from the periodicity of chain sublattice were detected. High-angle grain boundary or twinning formed by rotation of 33.3° around [100] direction was observed. High-resolution electron microscopy images revealed the stacking faults in ac planes.
12
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Magnetic and Structural Study of (ZnTe)/Co Core-Shell Nanowires Grown by Molecular Beam Epitaxy

64%
Misiuna P., Dłużewski P., Wojciechowski T., Lewińska S., Ślawska-Waniewska A., Wawro A., Wiater M., Wojtowicz T., Baczewski L.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
517-519
EN
Arrays of crystalline ZnTe nanowires grown by vapor-liquid-solid mechanism were covered with cobalt in a molecular beam epitaxy system. Magnetic and structural characterization of such core/shell nanowires was performed. Using scanning electron microscopy and transmission electron microscopy it was found that the mean shell thickness of cobalt was about 35% of the nominal deposition thickness. Deposited cobalt had a polycrystalline structure covering the ZnTe nanowires evenly along their length. With the increment of temperature during Co deposition the roughness of the nanowire sidewalls increases. Vibrating sample magnetometry measurements revealed that the magnetization easy-axis direction is perpendicular to the long axis of the nanowires, which is in agreement with theoretical predictions. Oxidation of Co shell does not change the anisotropy direction of such structures, however it increases their coercivity. Exchange bias effect at the interface of cobalt and cobalt oxides suggested by some authors is not responsible for such anisotropy orientation.
13
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Photoluminescence Properties of ZnO and ZnCdO Nanowires

52%
Zaleszczyk W., Fronc K., Aleszkiewicz M., Paszkowicz W., Wróbel J., Dłużewski P., Kret S., Klepka M., Kłopotowski Ł., Karczewski G., Wojtowicz T.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
357-362
EN
We report on the photoluminescence studies of ZnO and ZnCdO nanowires grown on SiO_2/Si substrates by low-pressure vapor phase synthesis. X-ray diffraction and transmission electron microscopy measurements show that the crystallographic structure of these ZnO and ZnCdO nanowires is of wurtzite-type with a high crystal perfection. Surface morphology of samples was determined by scanning electron microscopy and atomic force microscopy. The photoluminescence spectra of as-grown nanowires, nanowires extracted from the substrate and deposited onto Si wafer, and nanowires dispersed in ethanol by sonication were investigated at room temperature and compared to each other. The temperature dependence of the near band-gap photoluminescence emitted by the as-grown nanowires was also measured and analyzed.
14
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Do We Understand Magnetic Properties of ZnMnO?

52%
Godlewski M., Wójcik A., Kopalko K., Ivanov V., Wilamowski Z., Jakieła R., Guziewicz E., Szczepanik A., Dłużewski P., Chikoidze E., Barjon J., Dumont Y., Putkonen M., Niinistö L., Tang D.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
261-267
EN
Optical and magnetic properties of ZnMnO films are discussed based on the results of cathodoluminescence, photoluminescence, and magneto-photoluminescence investigations. We show that photoluminescence/cathodoluminescence emissions are strongly quenched and become in-plane inhomogeneous in samples with increased Mn fractions. Strong polarization of photoluminescence is observed, even though excitonic lines do not shift and are not split at magnetic fields up to 6 T.
15
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Growth and Properties of ZnMnTe Nanowires

46%
Zaleszczyk W., Janik E., Presz A., Szuszkiewicz W., Morhange J., Dłużewski P., Kret S., Kirmse H., Neumann W., Dynowska E., Domagała J., Caliebe W., Aleszkiewicz M., Pacuski W., Golnik A., Kossacki P., Baczewski L., Petroutchik A., Karczewski G., Wojtowicz T.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
351-356
EN
Catalytically enhanced growth of ZnMnTe diluted magnetic semiconductor nanowires by molecular beam epitaxy is reported. The growth is based on the vapor-liquid-solid mechanism and was performed on (001) and (011)-oriented GaAs substrates from elemental sources. X-ray diffractometry, scanning and transmission electron microscopy, atomic force microscopy, photoluminescence spectroscopy, and Raman scattering were performed to determine the structure of nanowires, their chemical composition, and morphology. These studies revealed that the obtained ZnMnTe nanowires possess zinc-blende structure, have an average diameter of about 30 nm, typical length between 1 and 2μm and that Mn^{2+} ions were incorporated into substitutional sites of the ZnTe crystal lattice.
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