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  1. 55 Acta Physica Polonica A

  2. 1 Biuletyn Polskiego Stowarzyszenia Wodoru i Ogniw Paliwowych

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  2. 1 2015

  3. 1 2013

  4. 2 2011

  5. 1 2010

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  1. 56 Story T.

  2. 17 Dobrowolski W.

  3. 12 Dziawa P.

  4. 12 Grodzicka E.

  5. 11 Knoff W.

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1
Content available remote

Correlations between Electronic and Magnetic Properties in Semimagnetic Semiconductors

100%
Story T.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 1
173-180
EN
Magnetic properties of IV-VI semimagnetic (diluted magnetic) semiconductors with Mn or with Gd can be controlled by changing the electronic parameters such as carrier concentration, Fermi level position or density of states at the Fermi level. The examples of these effects are the carrier concentration induced paramagnet-ferromagnet and ferromagnet-spin glass transitions in PbSnMnTe and the Fermi level position controlled Gd-Gd exchange interactions in SnGdTe.
2
Content available remote

IV-VI Semimagnetic Semiconductors with Rare Earth Ions

100%
Story T.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 4
663-672
EN
The electronic and magnetic properties as well as the applications of IV-VI semiconductors with rare earth ions of Eu and Yb are briefly discussed. The detailed analysis is presented of the recent experimental investigations of the magnetic and transport properties of IV-VI semimagnetic crystals with Gd. It concerns, in particular, the effect of Fermi level position controlled f-f exchange interaction between Gd ions in Sn_{1-x}Gd_{x}Te.
3
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IV-VI Semimagnetic Semiconductors: Recent Developments

100%
Story T.
Acta Physica Polonica A
|
1998
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vol. 94
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issue 2
189-197
EN
Recent developments in the field of semimagnetic IV-VI semiconductors are discussed with the emphasis on magnetic properties of bulk crystals with rare-earth ions (e.g., Sn_{1-x}Gd_{x}Te, Pb_{1-x} Ce_{x}Se, Pb_{1-x}Eu_{x}Te) and new low-dimensional magnetic multilayers (PbTe-EuTe and PbS-EuS). The other issues addressed, concern the new results in transport properties of ferromagnetic Pb_{1-x-y}Sn_{y}Mn_{x}Te, the observation of the Knight shift in electron paramagnetic resonance in PbTe:Mn and SnTe:Mn, and the thermoelectric properties of PbTe-Pb_{1-x}Eu_{x}Te quantum wells.
4
Content available remote

Semiconductor Ferromagnetic Structures

100%
Story T.
Acta Physica Polonica A
|
2000
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vol. 98
|
issue 3
171-181
EN
Ferromagnetic semiconductor structures such as superlattices or trilayers form a new class of magnetic systems composed entirely of semiconductor materials. The examples are Ga_{1-x}Mn_{x}As-AlGaAs with the ferromagnetic layer of GaMnAs semimagnetic (diluted magnetic) semiconductor or EuS-PbS with the ferromagnetic member (EuS) of the family of europium chalcogenides. We discuss the spectrum of perspective ferromagnetic semiconductor materials, the effect of size and stress on magnetic properties of ultrathin semiconductor ferromagnetic layers, and the effect of interlayer exchange in all-semiconductor systems.
5
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Magnetization of Pb_{1-x}Cr_{x}Te Semimagnetic Semiconductor

52%
Mac W., Story T., Twardowski A.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
492-494
EN
We present experimental studies of magnetization of Pb_{1-x}Cr_{x}Te (x ≤ 0.01) crystals. The reasonable description of the data is obtained for a composition of x ≤ 0.001 using Cr^{+++} model (Brillouin type paramagnetism S = 3/2).
6
Content available remote

Diluted Magnetic Semimetals - Beyond Heisenberg Coupling

52%
Wilamowski Z., Story T., Jantsch W.
Acta Physica Polonica A
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1995
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vol. 87
|
issue 1
189-192
EN
We analyse effects which cannot be explained assuming the isotropic Heisenberg form of sp-d or of the indirect d-sp-d (RKKY) coupling. Resonance line broadening, a line shift and an enhancement of the magnetic anisotropy in diluted magnetic semimetals are discussed.
7
Content available remote

On the Possible Origin of Large Value of Magnetic Anisotropy Constant in PbSnMnTe Mixed Crystals

52%
Łusakowski A., Story T., Gałązka R.
Acta Physica Polonica A
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1993
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vol. 84
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issue 4
829-831
EN
In PbSnMnTe crystals with the concentration of conducting holes of the order of 10^{21} cm^{-3}, the magnetic anisotropy constant K measured in ferromagnetic resonance experiments is nearly one order of magnitude larger than expected. In the present paper we investigate a contribution ΔK to the anisotropy constant, origin of which is the s-d interaction and the spin-orbit coupling.
8
Content available remote

Magnetic Anisotropy in (Ge,Mn)Te Layers

52%
Knoff W., Łusakowski A., Wołoś A., Story T.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 2
404-406
EN
Ferromagnetic resonance study of magnetic anisotropy is presented for thin layers of IV-VI diluted magnetic semiconductor (Ge,Mn)Te with Mn content of 12 and 21 at.% grown by molecular beam epitaxy on BaF₂ (111) substrates. The layers with low Mn content grow in the rhombohedral crystal structure and exhibit perpendicular magnetic anisotropy whereas the layers with Mn content higher than about 20 at.% are of cubic (rock-salt) structure and show regular easy-plane type magnetic anisotropy. The quantitative analysis of the angular dependence of the ferromagnetic resonant field is performed taking into account the magnetic energy contributions due to rhombohedral distortion (axial term along the (111) growth direction of the layer) and the crystal field terms allowed for ferromagnetic systems of rhombohedral symmetry.
9
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Interaction Between Magnetic Layers in Structures with Narrow-Gap IV-VI Semiconductors

52%
Dugaev V., Litvinov V., Dobrowolski W., Story T.
Acta Physica Polonica A
|
2000
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vol. 97
|
issue 3
455-458
EN
The results of calculation of the indirect exchange interaction between magnetic layers are presented for the case of a structure with narrow-gap semiconducting IV-VI quantum well. The main mechanism is a magnetic polarization of the size-quantized electrons and holes inside the well. This type of interaction is suggested for the explanation of recent experiments on EuS/PbS structures.
10
Content available remote

Photovoltaic Effect on PbTe p-n Junction in the Presence of Magnetic Field

46%
Le K., Grodzicka E., Witkowska B., Story T., Gałązka R.
Acta Physica Polonica A
|
1993
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vol. 84
|
issue 4
721-724
EN
Photovoltaic spectra of PbTe p-n junction have been measured in the infrared spectral region in the temperature range of 8-260 K. The p-n junctions have been formed by cadmium diffusion into the p-type PbTe crystals. From the positions of the photovoltaic maxima the energy gap of the diode material has been determined. In the presence of a magnetic field up to 7 T, a pronounced oscillatory behavior of the photovoltage was observed in the Faraday and Voigt configurations. Experiments were performed as a function of the magnetic field intensity at a constant wavelength of the incident light. The energy of the interband magnetooptical transitions between the Landau levels in PbTe was determined and compared with the theoretical model of Adler, describing the energy band structure for the IV-VI compounds.
11
Content available remote

Gd 4f and 5d Electrons in Sn_{0.96}Gd_{0.04}Te Valence Band

46%
Orłowski B. A., Kowalski B. J., Gołacki Z., Story T., Johnson R. L.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
857-860
EN
The synchrotron radiation was applied to measure resonant photoemission spectra (Fano-type Gd 4d-4f resonance), constant initial states and constant final states to study the valence band electronic structure of Sn_{0.96}Gd_{0.04}Te crystal. The resonant energy was found equal to 150.3 eV. The electrons 4f were found to contribute to the valence band of the crystal with the maximum located at 9.5 eV below the valence band edge whereas 5d electrons contribute at the crystal valence band edge.
12
Content available remote

Magnetic Susceptibility of PbSnMnTe in the Transition Region between Ferromagnetic and Spin Glass Phase

46%
Story T., Gałązka R., Eggenkamp P., Swagten H., de Jonge W.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 4
630-633
EN
The ac magnetic susceptibility (χ) was measured in the temperature range T = (1.5÷50) K for Pb_{1-x-y}Sn_{y}Mn_{x}Te samples with a composition y = 0.72, x = 0.015÷0.04 and carrier concentrations in the range p = (2.85÷14) × 10^{20} cm^{-3}. The breakdown of ferromagnetism and the formation of a spin glass phase are observed with an increasing carrier concentration. It is experimentally evidenced as continuous deviation of χ(T) from the characteristic critical behavior observed for ferromagnetic samples.
13
Content available remote

Electron Paramagnetic Resonance of Cr in PbTe

46%
Story T., Wilamowski Z., Grodzicka E., Witkowska B., Dobrowolski W.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 4
773-775
EN
We present the results of the low temperature electron paramagnetic resonance (EPR) and transport investigations of the crystals of Pb_{1-x}Cr_{x}Te (x ≤ 0.01). The samples with chromium concentrations x ≥ 0.0015 are all n-type. For these samples we observe the single EPR line with the g-factor decreasing from g = 1.97 till g = 1.93 with increasing carrier concentration. This resonance can be attributed to electrically and magnetically active Cr^{3+} ions. The crystals with Cr concentration x ≤ 0.0015 may be both n- and p-type. The EPR spectrum of these samples consists of two lines: the one discussed above and the other one with g = 1.99 observed only for samples with electron concentration n ≤ 10^{18} cm^{-3}.
14
Content available remote

Transport and Magnetic Properties of PbTe:Cr and PbSnTe:Cr

46%
Story T., Grodzicka E., Witkowska B., Górecka J., Dobrowolski W.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 5
879-881
EN
We present the results of the experimental studies of the low temperature transport and magnetic properties of PbTe, Pb_{1-x}Sn_{x}Te (x ≤ 0.3) and SnTe crystals doped with 0.5 at.% of chromium. Cr was found to be a resonant donor in PbTe and PbSnTe. Magnetic susceptibility measurements revealed that PbTe:Cr and Pb_{1-x}Sn_{x}Te:Cr (x ≤ 0.2) are Curie paramagnets whereas SnTe:Cr exhibits van Vleck paramagnetism.
15
Content available remote

Peculiarities of Electron Transport in PbTe:Cr due to Presence of Resonant Impurity State

46%
Grodzicka E., Dobrowolski W., Kossut J., Story T., Witkowska B.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
599-603
EN
The results of transport investigation of Pb_{1-x}Cr_{x}Te (x ≤ 0.009) in temperature range 3.5-300 K are presented. The obtained electron concentration and electron mobility vs. temperature and Cr concentration data are interpreted and discussed within the model assuming that Cr in PbTe forms a donor state resonant with the conduction band.
16
Content available remote

Magnetic Anisotropy in Pb_{1-x-y}Sn_{y}Mn_{x}Te Studied by Ferromagnetic Resonance

46%
Eggenkamp P., Story T., Swüste C., Swagten H., de Jonge W.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 4
641-644
EN
We will report on the anisotropy in (Pb)SnMnTe, studied by ferromagnetic resonance. We have found a cubic anisotropy with a = 73 × 10^{-4} cm^{-1} for Sn_{1-x}Mn_{x}Te and a = 200 × 10^{-4} cm^{-1} for Pb_{0.28-x}Sn_{0.72}Mn_{x}Te. We will indicate some possible explanations for this anomalously large anisotropy.
17
Content available remote

Magnetic Specific Heat Study of the Competition between Ferro- and Antiferromagnetic Spin-Spin exchange Interactions in PbSnMnTe

46%
Łazarczyk P., Jędrzejczak A., Story T., Arciszewska M., Gałązka R.
|
EN
Magnetic contribution to the specific heat, magnetic susceptibility and Hall effect are experimentally studied in Pb_{1-x-y}Sn_{y}Mn_{x}Te semimagnetic semiconductors with y=0.72 and x=0.08 and with different carrier concentrations 10^{20} ≤ p ≤ 10^{21} cm^{-3}. The ferromagnetism observed in crystals with p ≥ 3×10^{20} cm^{-3} breaks down with a decreasing concentration of carriers due to an increasing competition between Ruderman-Kittel-Kasuya-Yoshida and superexchange interactions.
18
Content available remote

New materials for thermoelectric generators based on PbTe-MnTe and PbTe-CdTe semiconductor alloys and nanocomposites

40%
Story T., Dybko K., Dziawa P., Mycielski A., Szczerbakow A., Szot M.
Biuletyn Polskiego Stowarzyszenia Wodoru i Ogniw Paliwowych
|
2011
|
issue 6
64-69
EN
New trends in the field of thermoelectrics are discussed for PbTe-based semiconductor thermoelectric materials exhibiting density of states engineering effects strongly enhancing thermoelectric power (PbMnTe) and spontaneous formation of nano-scale two-phase crystal structures (PbTeCdTe) – technologically scalable realization of electron crystal - phonon glass concept of new thermoelectric materials.
19
Content available remote

Magnetic Properties of EuS/PbS Semiconducting Structures

40%
Stachow-Wójcik A., Twardowski A., Story T., Dobrowolski W., Grodzicka E., Sipatow A.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 5
985-988
EN
We report results of magnetization study of EuS/PbS superstructures with different thicknesses of magnetic and nonmagnetic layers. Reduction of ferromagnetic phase transition temperature was found with decreasing EuS thickness. Reasonable description of this effect is obtained within the model based on the mean field approximation.
20
Content available remote

Evolution of Pb_{1-x}Cd_{x}Te Solid Solution Structure at High Temperatures

40%
Minikayev R., Dynowska E., Kamińska E., Szczerbakow A., Trots D., Story T., Szuszkiewicz W.
Acta Physica Polonica A
|
2011
|
vol. 119
|
issue 5
699-701
EN
The recent successful growth of single, bulk Pb_{1-x}Cd_{x}Te crystals by self-selecting vapor transport method at the Institute of Physics of the Polish Academy of Sciences in Warsaw opened new opportunities to study the physical properties of this interesting material in detail. In this work we report the preliminary results of X-ray powder diffraction studies performed on a set of Pb_{1-x}Cd_{x}Te solid solutions (where x ≤ 0.056) at high temperatures (295 K ≤ T ≤ 1100 K) and analyzed with the Rietveld refinement. Our results demonstrate the necessity of some correction of the relevant phase diagram and of the solubility limit, known from the literature.
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