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Conductivity Near the Metal-to-Insulator Transition in Cd_{1-x}Mn_{x}Se:Sc

100%
Głód P., Sawicki M., Lenard A., Dietl T., Plesiewicz W.
Acta Physica Polonica A
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1991
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vol. 79
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issue 2-3
389-392
EN
Earlier studies of transition metal impurities in II-VI compounds suggest that Sc acts as a resonant donor. We performed Hall effect and conductivity measurements of CdSe:Sc and Cd_{0.95}Mn_{0.05}Se:Sc. The results, particularly the critical concentration of the metal-to-insulator transition, turned out to be similar to those obtained previously for Cd_{1-x}Mn_{x}Se doped with hydrogenic-like impurities, such as In and Ga. Therefore, if the ground state of Sc impurity is indeed located above the bottom of the conduction band, our data demonstrate that the metal-to-insulator transition is primarily driven by the scattering, i.e. it corresponds to the Anderson localization.
2
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Metal-Insulator Transition in Zinc-Doped LaSrCuO

100%
Malinowski A., Cieplak M., Berkowski M., Plesiewicz W., Skośkiewicz T.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
617-621
EN
The magnetotransport in the vicinity of the metal-insulator transition in La_{1.85}Sr_{0.15}Cu_xZn_{1-x}O_4 is studied in the mK temperature range. Both longitudinal and transverse magnetoresistance are negative indicating the importance of spin effects. The magnitude of transverse magnetoresistance is larger than the magnitude of longitudinal magnetoresistance, indicating the absence of positive orbital magnetoresistance, in sharp contrast to strongly underdoped La_{2-x}Sr_xCuO_4. Both transverse and longitudinal magnetoresistance are proportional to the relative change of zero-field conductivity. This suggests that low-temperature localization of carriers may originate in the spin-disorder scattering on the spin droplets around Zn-impurities.
3
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Influence of Bound Magnetic Polarons on Magnetic and Electrical Properties in Metallic n-Cd_{0.95}Mn_{0.05}Se

86%
Głód P., Sawicki M., Dietl T., Skośkiewicz T., Lenard A., Plesiewicz W.
Acta Physica Polonica A
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1995
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vol. 87
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issue 1
173-175
EN
Doping-induced contribution to the millikelvin magnetic susceptibility of Cd_{0.95}Mn_{0.05}Se:In has been found to undergo a maximum at n ≈ 2n_{c}, and to vanish for n ≥ 8n_{c}, where n_{c} is the electron concentration corre­sponding to the metal-insulator transition. This confirms the presence, also in the metallic phase, of bound magnetic polarons. Their slow dynamics may account for hysteresis visible in our magnetoresistance data.
4
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Magnetoresistance of Si/Nb/Si Trilayers

73%
Zaytseva I., Cieplak M., Abal'oshev A., Dluzewski P., Grabecki G., Plesiewicz W., Zhu L., Chien C.
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issue 2
406-408
EN
We study the superconductor-insulator transition in Si/Nb/Si trilayers, in which the thickness of Si is fixed at 10 nm, and the nominal thickness of Nb changes in the range between d = 20 nm down to d = 0.3 nm. The transmission electron microscopy indicates the formation of the mixed Nb-Si layer for small d. Both the thickness-induced, and the magnetic-field induced superconductor-insulator transition is observed. The crossing point of the isotherms at the critical field B_{c} decreases with decreasing d, and it is T-independent at temperatures below 300 mK. At larger fields the weak peak in magnetoresistance appears in some of the films.
5
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Mesoscopic Phenomena in Microstructures of IV-VI Epilayers

73%
Grabecki G., Dietl T., Plesiewicz W., Lenard A., Skośkiewicz T., Kamińska E., Piotrowska A., Papis E., Frank N., Bauer G.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
551-554
EN
Magnetoresistance measurements of photolithographically patterned PbSe and Pb-{1-y}Mn_{x}Se microstructures were performed. Reproducible mag­netoconductance fluctuations with the amplitude increasing with decreasing temperature were observed. Unexpectedly, these fluctuations contain a com­ponent periodic in the magnetic field, and their magnitude is greater than that expected from the current theory of the universal conductance fluctua­tions. Possible explanations are discussed.
6
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Conductance Fluctuations in Microstructures of HgCdMnTe Bicrystals

73%
Grabecki G., Lenard A., Plesiewicz W., Jaroszyński J., Cieplak M., Skośkiewicz T., Dietl T., Kamińska E., Piotrowska A., Bulka B.
Acta Physica Polonica A
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1991
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vol. 80
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issue 2
307-310
EN
Microscopic four-contact probes to semimagnetic HgCdMnTe grain-boundary inversion layers have been photolithographically patterned. Magnetoresistance measurements performed on these samples revealed aperiodic conductance fluctuations of the magnitude of the order of e^{2}/h. Quantitative analysis of both fluctuation amplitude and their mean period indicate that we have approached the mesoscopic regime in our system. This opens new possibilities in studies of spin-subsystem dynamics in semimagnetic semiconductors.
7
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Second Harmonic Generation in Spin-Glass Microstructures and Fabrication of Microstructures in IV-VI Epilayers

59%
Grabecki G., Dietl T., Cieplak M., Plesiewicz W., Lenard A., Skośkiewicz T., Kamińska E., Piotrowska A., Żarecka R., Springholz G., Bauer G.
Acta Physica Polonica A
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1993
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vol. 84
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issue 4
781-784
EN
We studied magnetoconductance of two different mesoscopic systems: microregions containing two-dimensional electron gas adjacent to a grain-boundary plane in bicrystals of Hg_{0.79}Cd_{0.19}Mn_{0.02}Te and photolithographically patterned microstructures of Pb_{1-x}Mn_{x}Se. In both systems universal conductance fluctuations and generation of the second-harmonic voltage were observed at T ≤ 1 K. Moreover, in the former system the second harmonic signal exhibited distinct rise when the sample was cooled below the spin-glass freezing temperature (100 mK).
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