Wyniki wyszukiwania - Biblioteka Nauki

1

Magnetic Properties of (Zn,Mn)Te Semimagnetic Alloy Co-Doped with Chromium

100%

Avdonin A. , Van Khoi L. , Knoff W. , Gałązka R.

Acta Physica Polonica A

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2009

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tom 116

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nr 5

974-975

EN

Results of simultaneous doping of ZnTe with manganese and chromium are presented. An increase of magnetization of ferromagnetic Cr-related clusters with manganese concentration is observed. Phosphorus doping prevents the formation of ferromagnetic clusters.

2

Magnetic Properties of ZMTO Alloys

100%

Avdonin A. , Knoff W. , Gałązka R.

Acta Physica Polonica A

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2009

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tom 116

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nr 5

916-917

EN

The results of the magnetization and photoluminescence measurements of the ZMTO are presented. Under field cooling conditions a phase transition is observed. The dependence of the temperature of transition on oxygen concentration is analyzed. A model is proposed.

3

Magnetic Anisotropy in (Ge,Mn)Te Layers

100%

Knoff W. , Łusakowski A. , Wołoś A. , Story T.

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nr 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.

4

Studies of Diluted Magnetic Semiconductor Sn_{1-x-y-z}Ge_{x}Mn_{y}Gd_{z}Te

63%

Sichkovskyi V. , Radchenko M. , Lashkarev G. , Slyn'ko V. , Slyn'ko E. , Knoff W. , Domukhovski V. , Dziawa P. , Story T.

Acta Physica Polonica A

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2009

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tom 116

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nr 5

911-912

EN

Magnetization, anomalous Hall effect, thermoelectric power, magnetoresistance, and resistivity of Sn_{1-x-y-z}Ge_{x}Mn_{y}Gd_{z}Te (x = 0.039÷0.597, y = 0.077÷0.125, z = 0.0014÷0.028) mixed crystals were studied over the temperature range 4.2-300 K. The ferromagnetic order with Curie temperature 18-24 K was revealed.

5

Magnetization Studies of Antiferromagnetic Interlayer Coupling in EuS-SrS Semiconductor Multilayers

63%

Samburskaya T. , Sipatov A. , Volobuev V. , Dziawa P. , Knoff W. , Kowalczyk L. , Szot M. , Story T.

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nr 1

133-136

EN

Temperature and magnetic field dependence of magnetization of EuS-SrS multilayers grown epitaxially on KCl (001) substrate is experimentally studied by superconducting magnetometry technique. In these lattice-matched semiconductor heterostructures EuS layers are ferromagnetic quantum wells whereas SrS layers are nonmagnetic spacer barriers. The multilayers composed of EuS layers with thickness 3.5-5 nm and SrS layers (thickness 0.5-10 nm) exhibit ferromagnetic transition at 17 K. In the multilayers with ultrathin SrS spacers (0.5-1 nm) a nonmonotonic temperature dependence of magnetization as well as a characteristic switching in magnetic hysteresis loops is observed. These experimental findings are explained considering antiferromagnetic interlayer coupling between ferromagnetic EuS layers via nonmagnetic SrS spacers. The strength of this coupling is determined based on model magnetization calculations.

6

Photoemission Study of Mn 3d Electrons in the Valence Band of Mn/GeMnTe

63%

Pietrzyk M. , Kowalski B. , Orłowski B. , Knoff W. , Osinniy V. , Kowalik I. , Story T. , Johnson R.

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nr 2

275-281

EN

We present the results of the electronic band structure study of Ge_{0.9}Mn_{0.1}Te epilayers, clean and modified in situ by deposition of manganese atoms. The sets of resonant photoemission spectra were measured for the photon energy range covering the energy of Mn 3p→3d transition (45

7

Physical Properties of ZnCoO Tetrapods and Nanofibers

51%

Gas K. , Fronc K. , Dziawa P. , Knoff W. , Wojciechowski T. , Zaleszczyk W. , Baranowska-Korczyc A. , Morhange J. , Paszkowicz W. , Elbaum D. , Karczewski G. , Wojtowicz T. , Szuszkiewicz W.

Acta Physica Polonica A

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2009

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tom 116

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nr 5

868-870

EN

In this paper the physical properties of two types of Co-doped ZnO nanostructures: tetrapods and nanofibers grown by a rapid thermal evaporation process and prepared by the electrospinning technique, respectively, were investigated and analyzed. Surface morphology of the samples was examined using scanning electron microscopy. X-ray diffraction measurements showed hexagonal wurtzite crystal structure of both types of investigated nanostructures. Both X-ray diffraction and Raman scattering data confirmed high phase purity of the samples. The magnetic properties studied with the use of the SQUID magnetometer confirmed a presence of ferromagnetic order in analyzed nanostructures. The observed photoluminescence spectra exhibited two groups of lines. The first one, in the ultraviolet spectral range, is due to the optical transitions close to ZnO band gap, the second one in the red region is most probably related to the Co^{2+} d-d internal transitions. The influence of native defects on the optical properties is also shown and discussed. All results reported here lead us to the conclusion that in the mixed crystal nanostructures obtained, a fraction of the Zn^{2+} ions is substituted by Co^{2+} ions.

8

Ferromagnetic Transition in Ge_{1-x}Mn_{x}Te Layers

51%

Knoff W. , Domukhovski V. , Dybko K. , Dziawa P. , Jakieła R. , Łusakowska E. , Reszka A. , Świątek K. , Taliashvili B. , Story T. , Szałowski K. , Balcerzak T.

Acta Physica Polonica A

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2009

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tom 116

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nr 5

904-906

EN

Ferromagnetic transition temperature in thin layers of diluted magnetic (semimagnetic) semiconductor Ge_{1-x}Mn_{x}Te was studied experimentally by SQUID magnetometry method and analyzed theoretically for a model Ising-type diluted magnetic system with Ruderman-Kittel-Kasuya-Yosida indirect exchange interaction. The key features of the experimentally observed dependence of the Curie temperature on Mn content (x ≤ 0.12) and conducting hole concentration p = (1-10) × 10^{21} cm^{-3} were reproduced theoretically for realistic valence band and crystal lattice parameters of p-Ge_{1-x}Mn_{x}Te taking into account short carrier mean free path encountered in this material and Ruderman-Kittel-Kasuya-Yosida mechanism with both delta-like and diffused character of spatial dependence of the exchange coupling between magnetic ions and free carriers.

9

Magnetic and Structural Studies of GeMnSnTe Epitaxial Layers

51%

Grochot A. , Knoff W. , Taliashvili B. , Wołkanowicz W. , Minikayev R. , Pieniążek A. , Łusakowska E. , Sawicki M. , Jantsch W. , Story T. , Przybylińska H.

Acta Physica Polonica A

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2017

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tom 132

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nr 2

340-342

EN

MBE grown Ge_{1-x-y}Mn_xSn_yTe layers with Mn content ranging from 10 to 30% and Sn content ranging from 2 to 5% have been characterized with X-ray diffraction, energy-dispersive X-Ray spectroscopy, atomic force microscopy, SQUID magnetometry, and ferromagnetic resonance. All layers (except the one with the highest Mn and Sn content) were found to be single phase rhombohedral, with the distortion axis perpendicular to the layer surface, and ferromagnetic. Ferromagnetic resonance studies have shown that co-doping with a few percent of tin makes the lattice more rigid and changes considerably the magnetocrystalline anisotropy, from purely uniaxial in GeMnTe to distorted cubic in Ge_{1-x-y}Mn_xSn_yTe at the same Mn content.