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Wyświetlanie 1-25 z 196
Tytuł:
Second-Order Phase Transitions in Magnetic Ca₃Al₂(SiO₄)(Oₕ¹⁰) and Non Magnetic Cubic ZnO
Autorzy:
Kunert, H.
Powiązania:
https://bibliotekanauki.pl/articles/1386491.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
Possible symmetry of modes those may cause transitions in magnetic and non magnetic crystals as well as lower space subgroup symmetries of the crystals have been found. The Landau-Lifshitz theory for non magnetic crystals has been reformulated for magnetic crystals and has been applied to Ca₃Al₂(SiO₄)(Oₕ¹⁰). Some experimental data confirm our results.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 439-441
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Defect-Related Origin of the Ferromagnetism in ZnO:Co
Autorzy:
Hanafin, R.
Pemmaraju, C.
Archer, T.
Sanvito, S.
Powiązania:
https://bibliotekanauki.pl/articles/1810514.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
In recent years transition metal ion doped ZnO has been the focus of intense scientific enquiry. ZnO:Co is by far the most studied member of this family. However, despite the many experimental claims for ferromagnetism, a definitive theoretical explanation for long range magnetic interaction has so far been lacking. Here we present a mechanism which describes not only the origin of this previously inexplicable magnetism but also explains the experimental findings to date and in addition, suggests a recipe for tailoring the magnetic properties. We demonstrate that the magnetism originates from a $Co^{2+}$ oxygen vacancy pair with a partially filled level close to the ZnO conduction band minimum. The long range coupling then occurs via conduction electrons at moderate n doping. This however is not sufficient for room temperature ferromagnetism due to the prohibitive concentrations of O vacancies needed. The experimental findings may then be explained by a combination of our proposed mechanism and the formation of blocked superparamagnetic clusters.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 263-265
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of EuS/PbS Semiconducting Structures
Autorzy:
Stachow-Wójcik, A.
Twardowski, A.
Story, T.
Dobrowolski, W.
Grodzicka, E.
Sipatow, A.
Powiązania:
https://bibliotekanauki.pl/articles/1968421.pdf
Data publikacji:
1997-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
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.
Źródło:
Acta Physica Polonica A; 1997, 92, 5; 985-988
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature Dependence of the Energy Gap in Cd$\text{}_{1-x}$Fe$\text{}_{x}$Se
Autorzy:
Gaj, J. A.
Nguyen, The Khoi
Arciszewska, M.
Lebecki, K.
Powiązania:
https://bibliotekanauki.pl/articles/1891022.pdf
Data publikacji:
1991-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
The energy gap and magnetic susceptibility of Cd$\text{}_{0.85}$Fe$\text{}_{0.15}$Se were measured in function of temperature. Experiments showed that the magnetic contribution to the variation of the energy gap in Cd$\text{}_{1-x}$Fe$\text{}_{x}$Se is not proportional to the product of magnetic susceptibility and temperature as it has been observed in Mn$\text{}^{++}$-containing semiconductors.
Źródło:
Acta Physica Polonica A; 1991, 80, 3; 405-407
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Susceptibility and Charge State of Gd Impurity in Pb$\text{}_{1-x}$Sn$\text{}_{x}$Te⟨Gd⟩ Crystals
Autorzy:
Zayachuk, D. M.
Ivanchuk, R. D.
Kempnyk, V. I.
Mikityuk, V. I.
Powiązania:
https://bibliotekanauki.pl/articles/1952432.pdf
Data publikacji:
1996-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
The effective magnetic momentum p$\text{}_{eff}$ of Gd-impurities in the Pb$\text{}_{1-x}$Sn$\text{}_{x}$Te⟨Gd⟩ crystals as a function of crystal composition x with 0 ≤ x ≤ 0.25 is studied. It is shown that with the increase in tin content in the crystals from 0 to 0.15, p$\text{}_{eff}^{2}$(Gd) increases slowly from 37 to 43. Then p$\text{}_{eff}^{2}$(Gd) increases abruptly to 63 value when x = 0.16±0.01. For subsequent increase x ≥ 0.17 p$\text{}_{eff}^{2}$(Gd) remains constant at 63. Possible reasons of observed changes of p$\text{}_{eff}$(Gd) and possible mechanisms of influence of the Pb$\text{}_{1-x}$Sn$\text{}_{x}$Te crystal field on the effective magnetic momentum value of Gd-impurities in the crystals under study are analysed.
Źródło:
Acta Physica Polonica A; 1996, 90, 5; 985-988
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Photoluminescence Study in PbS-EuS Superlattices
Autorzy:
Kowalczyk, L.
Sadowski, J.
Gałązka, R. R.
Stachow-Wójcik, A.
Sipatov, A. Yu.
Volobuev, V. V.
Smirnov, V. A.
Dugaev, V. K.
Powiązania:
https://bibliotekanauki.pl/articles/1991612.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
Investigations of the photoluminescence of PbS-EuS superlattices deposited on (111)BaF$\text{}_{2}$ substrates are presented. Quantum-size and deformation effects in photoluminescence spectra are observed. The strain-induced gap shift and valence-band offset is determined from experimental results. A strong stimulated photoluminescence with relatively low threshold was observed. It was found that the photocarriers generated in EuS barrier strongly affect the population of PbS subbands.
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 397-400
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Faraday Rotation and Photoionization of ZnCrSe Semimagnetic Semiconductor
Autorzy:
Mac, W.
Nguyen, The Khoi
Gaj, J. A.
Twardowski, A.
Demianiuk, M.
Stachow-Uciakowska, A.
Powiązania:
https://bibliotekanauki.pl/articles/1929663.pdf
Data publikacji:
1993-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
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.
Źródło:
Acta Physica Polonica A; 1993, 84, 3; 567-570
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exchange Interaction in ZnCrSe Semimagnetic Semiconductor
Autorzy:
Mac, W.
Nguyen, The Khoi
Twardowski, A.
Gaj, J. A.
Demianiuk, M.
Powiązania:
https://bibliotekanauki.pl/articles/1924249.pdf
Data publikacji:
1992-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
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$\text{}_{0}$α-N$\text{}_{0}$β=0.67eV.
Źródło:
Acta Physica Polonica A; 1992, 82, 5; 902-904
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High Temperature Ferromagnetism and Nano-Scale Phase Separations in Diluted Magnetic Semiconductors and Oxides
Autorzy:
Dietl, T.
Powiązania:
https://bibliotekanauki.pl/articles/2047208.pdf
Data publikacji:
2007-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
In this paper the present understanding of the origin of ferromagnetic response that has been detected in a number of diluted magnetic semiconductors and diluted magnetic oxides at room temperature is outlined. It is argued that in these systems, owing to a typically small solubility of magnetic ions, crystallographic or chemical phase separation into regions with a large and a small concentration of magnetic component takes place. The ferromagnetic signatures then come from the regions with a large concentration of magnetic ions, which show non-zero spontaneous magnetization up to the blocking temperature, whose magnitude is proportional to the nanocrystal volume and magnetic anisotropy. Novel methods enabling a control of nano-assembling of magnetic nanocrystals in non-conducting matrices as well as possible functionalities of these spatially modulated magnetic systems are described. We also discuss phase separations into paramagnetic and ferromagnetic regions, which are driven by the Anderson-Mott localization and/or competing ferromagnetic and antiferromagnetic interactions. Finally, the question whether the high temperature ferromagnetism is possible in materials without magnetic ions is addressed.
Źródło:
Acta Physica Polonica A; 2007, 111, 1; 27-46
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Direct Measurements of Bound Magnetic Polaron Magnetization in Ga-Doped Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te
Autorzy:
Stankiewicz, J.
Palacio, F.
Villuendas, F.
Powiązania:
https://bibliotekanauki.pl/articles/1968418.pdf
Data publikacji:
1997-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
Light induced remanent changes in magnetization of n-type Cd$\text{}_{1-x}$Mn$\text{}_{x}$ Te (x=0.01, 0.05) single crystals have been measured at T=2 and 5 K and in magnetic fields of up 0.5 T. The effect observed gradually saturates with increasing magnetic field. It also correlates with light induced increase in shallow donor concentration measured on the same samples. The bound magnetic polaron theory accounts for the temperature and magnetic field variations of the persistent magnetization. There are no fitting parameters.
Źródło:
Acta Physica Polonica A; 1997, 92, 5; 976-980
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of Epitaxial (Ge,Mn)Te Thin Films with Varying Crystal Stoichiometry
Autorzy:
Knoff, W.
Domukhovski, V.
Dybko, K.
Dziawa, P.
Górska, M.
Jakieła, R.
Łusakowska, E.
Taliashvili, B.
Story, T.
Reszka, A.
Anderson, J.
Rotundu, C.
Powiązania:
https://bibliotekanauki.pl/articles/1811940.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
Magnetization of 1 μm thick ferromagnetic IV-VI (Ge, Mn)Te semiconductor layers with 10 at.% of Mn was studied by SQUID magnetometry method up to the magnetic fields of 70 kOe. The layers were grown on BaF₂ (111) substrates by molecular beam epitaxy with varying Te molecular flux, which permitted the control of layer stoichiometry and conducting hole concentration. X-ray diffraction and in situ electron diffraction characterization of layer growth and crystal structure revealed two-dimensional mode of growth and monocrystalline rhombohedral crystal structure of (Ge, Mn)Te layers. Controlling the layer stoichiometry influences the temperature dependence of magnetization with the ferromagnetic Curie temperature varying in $Ge_{0.9}Mn_{0.1}Te$ layers from $T_c$=30 K (low Te flux) to $T_c$=42 K (high Te flux).
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1159-1165
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Second-Order Phase Transitions in Non-Magnetic Wurtzite ZnO and Magnetic Doped with Co
Autorzy:
Kunert, H.
Niyongabo, P.
Powiązania:
https://bibliotekanauki.pl/articles/1385751.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
Opis:
We investigate the second-order phase transitions in non-magnetic wurtzite ZnO and magnetic doped with cobalt. Using reformulated Landau-Lifshitz theory of second-order phase transitions and our computer program, we have found all possible lower space group symmetries of ZnO and ZnO doped with Co as well as symmetries of vibration modes which may cause structural phase transitions. We interpret the Raman phonon modes of magnetic doped ZnO according to corepresentations of the magnetic space group P6'₃m'c (ZnO magnetic). Some experimental techniques like X-ray diffraction, reflectivities and Raman spectroscopies can verify our theoretical results.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 400-403
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Specific Heat Study of the Competition between Ferro- and Antiferromagnetic Spin-Spin exchange Interactions in PbSnMnTe
Autorzy:
Łazarczyk, P.
Jędrzejczak, A.
Story, T.
Arciszewska, M.
Gałązka, R. R.
Powiązania:
https://bibliotekanauki.pl/articles/1952041.pdf
Data publikacji:
1996-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.50.Lk
Opis:
Magnetic contribution to the specific heat, magnetic susceptibility and Hall effect are experimentally studied in Pb$\text{}_{1-x-y}$Sn$\text{}_{y}$Mn$\text{}_{x}$Te semimagnetic semiconductors with y=0.72 and x=0.08 and with different carrier concentrations 10$\text{}^{20}$ ≤ p ≤ 10$\text{}^{21}$ cm$\text{}^{-3}$. The ferromagnetism observed in crystals with p ≥ 3×10$\text{}^{20}$ cm$\text{}^{-3}$ breaks down with a decreasing concentration of carriers due to an increasing competition between Ruderman-Kittel-Kasuya-Yoshida and superexchange interactions.
Źródło:
Acta Physica Polonica A; 1996, 90, 5; 891-894
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Spin-Glass Phase Formation on Exciton Magnetic Polaron in (Cd,Mn)Te
Autorzy:
Chudnovskiy, A.L.
Rosenow, B.
Oppermann, R.
Yakovlev, D. R.
Zehnder, U.
Ossau, W.
Powiązania:
https://bibliotekanauki.pl/articles/1950742.pdf
Data publikacji:
1996-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Lk
75.50.Pp
Opis:
The influence of the spin-glass phase formation of the (Cd,Mn)Te semimagnetic layers on properties of the exciton magnetic polaron were investigated both theoretically and experimentally. The theoretical model offers a consistent description of the temperature dependence of the exciton magnetic polaron energy in the vicinity of spin-glass transition and shows good agreement with the experimental data.
Źródło:
Acta Physica Polonica A; 1996, 90, 4; 755-758
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Concentration Dependence of Photo-Induced Magnetization in Diluted Magnetic Semiconductor Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te
Autorzy:
Yamaguchi, Y.
Kawai, H.
Sato, T.
Powiązania:
https://bibliotekanauki.pl/articles/1956517.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Lk
75.50.Pp
Opis:
The photo-induced decrease in magnetization ΔM$\text{}_{photo}$ was observed in Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te (0.25 < x < 0.42) under unpolarized light illumination whose photon energy is smaller than the band gap of the sample. The photo-induced magnetization decreases with increasing Mn content through Mn$\text{}^{2+}$-Mn$\text{}^{2+}$ antiferromagnetic interaction, which supports our idea for origin of it based on the flipping of Mn spins in the bound magnetic polarons accompanied by the spin-flip Raman scattering.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 479-482
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conductivity and Magnetism of Magnetic Oxides
Autorzy:
Gehring, G. A.
Powiązania:
https://bibliotekanauki.pl/articles/2012877.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.50.Gg
Opis:
In a stoichiometric oxide the energy for the magnetic ordering is due to superexchange. This depends on the virtual transfer of a d electron from the transition ion to the neighbouring oxygen. When the oxide is p-doped there are compensating holes on the oxygen or the transition ion becomes mixed valent. The oxide may then conduct. The same transfer integral enters both the expression for the antiferromagnetic superexchange and the band width of the mobile carriers. Thus materials with a large antiferromagnetic exchange energy will be expected to have a relatively wide conduction band in the doped state and hence to have a high conductivity. In this paper the difference is explored between the materials in which there is true antiferromagnetism and those which are ferrimagnetic. In the antiferromagnets the carriers must destroy the magnetic order as they move. This behaviour is well known from the cuprates. In ferrimagnets the carriers may be able to move entirely on one sublattice. This occurs in Fe$\text{}_{3}$O$\text{}_{4}$ and probably in the doped garnets. In the case where motion is on one sublattice then doping does not destroy the magnetism and there is a relatively small magnetoresistance. An interesting feature is that unlike the cuprates the ferrimagnets do not become good metals at any doping but exhibit hopping conductivity. We explain the apparent paradox that the best conductivity is actually observed in materials where the conduction is only allowed when the antiferromagnetism has been quenched and that the conductivity in ferrimagnets is low.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 175-184
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Susceptibility of PbSnMnTe in the Transition Region between Ferromagnetic and Spin Glass Phase
Autorzy:
Story, T.
Gałązka, R. R.
Eggenkamp, P. J. T.
Swagten, H. J. M.
de Jonge, W. J. M.
Powiązania:
https://bibliotekanauki.pl/articles/1920980.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.50.Lk
Opis:
The ac magnetic susceptibility (χ) was measured in the temperature range T = (1.5÷50) K for Pb$\text{}_{1-x-y}$Sn$\text{}_{y}$Mn$\text{}_{x}$Te samples with a composition y = 0.72, x = 0.015÷0.04 and carrier concentrations in the range p = (2.85÷14) × 10$\text{}^{20}$ cm$\text{}^{-3}$. 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.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 630-633
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transport and Magnetic Properties of Pb$\text{}_{1-x-y}$Sn$\text{}_{y}$Mn$\text{}_{x}$Te (x ≤ 0.16)
Autorzy:
Łazarczyk, P.
Grodzicka, E.
Arciszewska, M.
Witkowska, B.
Dynowska, E.
Miotkowska, S.
Story, T.
Powiązania:
https://bibliotekanauki.pl/articles/1876221.pdf
Data publikacji:
1995-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.50.Lk
Opis:
Hall constant, conductivity and magnetic susceptibility of Pb$\text{}_{1-x-y}$Sn$\text{}_{y}$Mn$\text{}_{x}$Te semimagnetic semiconductor were investigated as a function of Mn content (x = 0.04, 0.09, 0.16, y = (0.7-0.8)) in the temperature range T = (4 - 300) K. A ferromagnetic phase transition takes place at T = 5 K for samples with x = 0.04, at T = 10 K for x = 0.09 and at T = 20 K for x = 0.16. For crystals with x ≥ 0.09 the strong temperature dependence of the Hall constant is observed for temperatures below 40 K. Magnetic field characteristics of the Hall effect is strongly non-linear at T = 4.2 K. No significant temperature or magnetic field dependence of conductivity is observed in the whole temperature range studied. The observed transport anomalies are due to the anomalous Hall effect.
Źródło:
Acta Physica Polonica A; 1995, 87, 2; 469-472
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Epitaxial Strain on Magnetic Anisotropy in (Ga,Mn)As
Autorzy:
Juszyński, P.
Wasik, D.
Gryglas-Borysiewicz, M.
Przybytek, J.
Szczytko, J.
Twardowski, A.
Sadowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1403622.pdf
Data publikacji:
2012-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.47.-m
Opis:
Two (Ga,Mn)As samples having different magnetic anisotropy (one with in-plane easy axis and another one with out-of-plane easy axis) were studied by means of magnetotransport experiments. Anisotropy field B_{A} was determined for both samples as a function of temperature. For the sample having in-plane easy axis, an inversion of the direction of planar Hall effect hysteresis was observed upon increase of temperature. This result was simulated using the Stoner-Wohlfarth model.
Źródło:
Acta Physica Polonica A; 2012, 122, 6; 1004-1006
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Static and Dynamic Spin Organization in Magnetic Semiconductor Nanostructures
Autorzy:
Samarth, N.
Luo, H.
Furdyna, J. K.
Giebultowicz, T. M.
Awschalom, D. D.
Powiązania:
https://bibliotekanauki.pl/articles/1920966.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.25.+z
Opis:
We describe experiments which study static and dynamic aspects of Mn spin organization in magnetic semiconductor superlattices and quantum wells. Neutron diffraction studies of ZnSe/MnSe and ZnTe/MnSe superlattices show how static Mn spin organization in these antiferromagnetic layers may be modified by strain and lowered dimensionality. We also use a novel form of femtosecond magnetic spectroscopy to examine magnetic polaron dynamics in diluted magnetic semiconductor quantum wells, and show how the organization of Mn spins by a spin-polarized carrier population may be directly viewed in the time domain.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 573-584
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetic Exchange in Diluted Magnetic Semiconductors of Wurtzite Structure
Autorzy:
Blinowski, J.
Kacman, P.
Powiązania:
https://bibliotekanauki.pl/articles/1929720.pdf
Data publikacji:
1993-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.30.-m
Opis:
Kinetic exchange between valence electrons and paramagnetic ions in diluted magnetic semiconductors of wurtzite structure is examined and compared with the results obtained previously for zinc-blende type diluted magnetic semiconductors. Two limiting electron configurations of the impurity ion, d$\text{}^{5}$ and d$\text{}^{1}$, are discussed. For the former, it is shown that the exchange constant anisotropy, experimentally observed in CdMnSe, results from the anisotropy of the hybridization matrix elements. In the latter case, apart from the similar anisotropy of the ferromagnetic exchange constant, additional, antiferromagnetic corrections should be expected, since for this particular symmetry the hybridization between the ground state of the ion and valence band becomes allowed.
Źródło:
Acta Physica Polonica A; 1993, 84, 4; 693-696
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Slow Relaxation of Resistance in Manganite Perovskite Nanoconstrictions
Autorzy:
Baszyński, J.
Powiązania:
https://bibliotekanauki.pl/articles/1810570.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.60.Lr
75.50.Pp
Opis:
The time decay of the surface resistance $R_{S}(t)$ was measured for the $La_{0.7}Sr_{0.3}MnO_{3}$ perovskite nanocontacts obtained by break technique at liquid nitrogen. The corresponding time relaxation can be described by two-term formula: stretched exponential function and logarithmic dependence. The characteristic times $τ_{1}$ and $τ_{2}$ of the relaxation processes are of order of seconds and few tens of seconds, respectively. The appearance of both contributions evidences the existence of two sources of relaxation, which can be assigned to inhomogeneous changes of the angle between the magnetic moments of the neighboring Mn ions inside spin blocks $(τ_{1})$ and between the spin blocks $(τ_{2})$ occurring near surface of the nano-electrodes. Similar to magnetic viscosity, the dependence of resistance viscosity $S_{R}$ on basis current is characterized by bell-shaped curve. These results point out the important role of the structural arrangements of the Mn-ions into spin blocks on the surfaces electrodes of the nanocontact.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 339-341
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Site Percolation Thresholds of FCC Lattice
Autorzy:
Gawron, T. R.
Cieplak, Marek
Powiązania:
https://bibliotekanauki.pl/articles/1891423.pdf
Data publikacji:
1991-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Mg
75.50.Pp
Opis:
Percolation thresholds, p$\text{}_{c}$, for site diluted spin systems on the fcc lattice are determined for exchange interactions extending up to the shell of the fourth nearest neighbors. If the interactions include the nearest, second, third, and fourth neighbors, p$\text{}_{c}$ is equal to 0.198, 0.136, 0.061, and 0.05 respectively. These results agree with the Roberts approximate formula for p$\text{}_{c}$. Estimation of p$\text{}_{c}$ to even longer-ranged couplings is presented. For instance for p$\text{}_{c}$ = 0.01 the range of the couplings should extend at least to the eight shell of neighbors.
Źródło:
Acta Physica Polonica A; 1991, 80, 3; 461-464
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of GaMnAs Single Layers and GaInMnAs Superlattices Investigated at Low Temperature and High Magnetic Field
Autorzy:
Hernandez, C.
Terki, F.
Charar, S.
Sadowski, J.
Maude, D.
Stanciu, V.
Svedlindh, P.
Powiązania:
https://bibliotekanauki.pl/articles/2036030.pdf
Data publikacji:
2003-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.70.-i
Opis:
Magnetotransport properties of GaMnAs single layers and InGaMnAs/InGaAs superlattice structures were investigated at temperatures from 4 K to 300 K and magnetic fields up to 23 T to study the influence of carriers confinement through different structures. Both single layers and superlattice structures show paramagnetic-to-ferromagnetic phase transition. In GaMnAs/InGaAs superlattice beside the Curie temperature (T$\text{}_{c}$≈40 K), a new phase transition is observed close to 13 K.
Źródło:
Acta Physica Polonica A; 2003, 103, 6; 613-619
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
EPR Spectra of Cr in CdTe Crystals
Autorzy:
Stefaniuk, I.
Bester, M.
Virt, I. S.
Kuzma, M.
Powiązania:
https://bibliotekanauki.pl/articles/2043654.pdf
Data publikacji:
2005-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.30.Cr
Opis:
The EPR studies of CdTe:Cr were performed on X-band (9.6 GHz) spectrometer at room temperature. Single CdTe crystals were doped by chromium Cr in the synthesis process. The spectra observed were resolved into two spectra. The first one consisted of very broad line (Δ B=100 mT) and the second one showed a typical fine structure. The complete angular dependence measurements were obtained. The fine structure of Cr$\text{}^{2+}$ or Cr$\text{}^{3+}$ ions was assumed and simulated. It follows from the theoretical analysis of the obtained spectra that degree of ionization of the chromium Cr dopant is 3+.
Źródło:
Acta Physica Polonica A; 2005, 108, 2; 413-418
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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