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1
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Hopping Conductivity in (Zn,Fe)Se Intentionally Doped with Ag

100%
Zaręba A., Demianiuk M.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 5
749-752
EN
The transport phenomena in (Zn,Fe)Se were studied. In order to obtain iron centers in Fe^{3+} charge state the crystals were doped by Ag what produces acceptors compensating Fe^{2+} donors. The results are explained in terms of thermally activated jumping of charges between Fe^{3+} and Fe^{2+} centers. The nature of activation energy is discussed. The polaron model seems to be not valid in our case. The Coulomb interaction between charged acceptors and "holes" on iron centers is considered as the origin of thermal activation of jumps. We suggest the deviation from random and mutually independent distributions of charged Ag acceptors and Fe^{3+} ions resulting from the electrostatic interactions between them at high temperatures.
2
Content available remote

Magnetic Anisotropy of V^{++} in CdS

81%
Herbich M., Mac W., Twardowski A., Demianiuk M.
Acta Physica Polonica A
|
1996
|
vol. 90
|
issue 4
809-812
EN
The magnetization measurements at magnetic field up to 6 T obtained from newly grown hexagonal Cd_{1-x}V_{x}S (x ≈ 0.0004) are presented. The strong anisotropy of magnetization is observed at low temperatures (1.6 < T < 20 K). The data are well described by the crystal field model calculations taking into account static trigonal Jahn-Teller distortion and spin-orbit coupling.
3
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Photoneutralization of the Fe^{3+} Centers in the ZnSe Crystals Heavily Doped with Iron

81%
Lubomirska-Wittlin A., Szadkowski A. J., Demianiuk M.
Acta Physica Polonica A
|
1991
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vol. 79
|
issue 2-3
337-340
EN
Photoconductivity and optical quenching of the photoconductivity were measured. The photoneutralization of the Fe^{3+} centres has been found to occur for photon energies down to 0.8 eV (i.e. the threshold can not be at 1.1 eV, as often quoted). The conclusion from our previous paper that the lattice relaxation energy is small, has been confirmed. It has to be smaller than 0.1 eV.
4
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High-Field EPR of Zn_{1-x}Cr_{x}Te

71%
Boonman M. E. J., Mac W., Wittlin A., Twardowski A., Demianiuk M.
Acta Physica Polonica A
|
1995
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vol. 88
|
issue 5
829-832
EN
High magnetic field electron paramagnetic resonance experiments have been performed on Zn_{1-x}Cr_{x}Te covering the energy range 1-7 cm^{-1} in fields up to 20 T at T = 1.2 K. The static magnetic field was oriented along the (100), (110) and (111) crystallographic axes of the sample. Pronounced absorption lines for intra-chromium transitions have been observed for these different orientations, revealing a strong anisotropy due to a static Jahn-Teller distortion. The measured low energy level structure of the Cr^{++} ion can be described by a cubic crystal field model including this distortion of the Cr centers.
5
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Exchange Interaction in ZnCrSe Semimagnetic Semiconductor

71%
Mac W., Nguyen K., Twardowski A., Gaj J., Demianiuk M.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 5
902-904
EN
Magnetoreflectance and magnetization of ZnCrSe were measured for B ≤ 5 T and T = 2 K. A linear dependence between exciton splitting and magnetization was found. The s, p-d exchange parameter was estimated: N_{0}α-N_{0}β=0.67eV.
6
Content available remote

Specific Heat of Cr-Based Semimagnetic Semiconductors

71%
Twardowski A., Eggenkamp P., Mac W., Swagten H., Demianiuk M.
Acta Physica Polonica A
|
1993
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vol. 84
|
issue 3
563-565
EN
Specific heat of ZnCrSe and ZnCrS was measured for 1.5 < T < 10 K and B < 3 T. The data were interpreted using "crystal field model" taking into account tetrahedral crystal field, tetragonal Jahn-Teller distortion and spin-orbit interaction.
7
Content available remote

Exchange Parameters of CdCrS Semimagnetic Semiconductor

71%
Herbich M., Mac W., Twardowski A., Ando K., Demianiuk M.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 4
774-776
EN
Free exciton magnetoreflectance and magnetization of Cd_{1-x}Cr_{x}S (0.0024 < x < 0.0031) were measured at T = 2.0 K and magnetic field up to 5 T. Combining the heavy hole exciton splitting with the magnetization data the exchange integral N_{0}β = +0.46±0.04 eV was evaluated within the framework of mean field approximation.
8
Content available remote

s,p-d Exchange Constants of ZnFeTe Diluted Magnetic Semiconductor

62%
Mac W., Herbich M., Khoi N. T., Twardowski A., Shapira Y., Demianiuk M.
Acta Physica Polonica A
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1995
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vol. 88
|
issue 5
845-848
EN
Reflectance and degree of polarization of reflectance of the free exciton in Zn_{1-x}Fe_{x}Te (x ≈ 0.002) was measured at T = 1.9 K and magnetic field up to 5 T. Combining the exciton splitting with the magnetization data we estimated the exchange constant N_{0}(α-β) = 2.1 eV.
9
Content available remote

Exciton Dynamics in ZnTe Based Semimagnetic Semiconductors and CdMnTe Quantum Wells

62%
The Khoi N., Gaj J., Karczewski G., Wojtowicz T., Kossut J., Demianiuk M.
Acta Physica Polonica A
|
1996
|
vol. 90
|
issue 5
899-902
EN
Inelastic scattering of excitons on LO phonons in ZnTe based bulk semimagnetic semiconductors with low concentration of paramagnetic ions (Mn^{2+}, Fe^{2+} and Cr^{2+}) was studied. A polarization degree of the LO phonon Raman lines was measured as a function of the exciton splitting in a magnetic field, and allowed us to determine the polarization lifetime (polariton flight time). A similar method was used to investigate multiple Mn^{2+} spin-flip scattering in CdMnTe quantum well. The cascade model seems to be not adequate to interpret the dependence of the polarization degree on the order of scattering.
10
Content available remote

Faraday Rotation and Photoionization of ZnCrSe Semimagnetic Semiconductor

62%
Mac W., Nguyen K., Gaj J., Twardowski A., Demianiuk M., Stachow-Uciakowska A.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
567-570
EN
The magnetoabsorption and the Faraday rotation of ZnCrSe were measured for B ≤ 5 T and T = 2 K in the region of photon energies lower than the fundamental absorption edge. The circular dichroism of the photoionization absorption bane was observed and analyzed. The Faraday rotation was interpreted as due to the sum of contributions from interband and photoionization optical transitions.
11
Content available remote

Effects of the Spin-Dependent Potential fluctuations on Free Exciton Zeeman Splitting of Zn_{1-x}Mn_{x}Se

62%
Herbich M., Mac W., Stachow A., Twardowski A., Tworzydło J., Demianiuk M.
Acta Physica Polonica A
|
1996
|
vol. 90
|
issue 4
813-816
EN
Magnetoreflectance of free exciton and magnetization in Zn_{1-x}Mn_{x}Se (0.0007 < x < 0.12) were measured. The evaluated proportionality factor between the exciton splitting and the magnetization showed a strong concentration dependence. This effect cannot be explained within the mean field approximation and the virtual crystal approximation and it was described within the model including chemical and magnetic disorder.
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