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Wyszukujesz frazę "Łusakowski, A." wg kryterium: Autor


Tytuł:
On the Possible Analogy between Spin-Glasses and Systems
Autorzy:
Łusakowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1920977.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Nr
71.55.Dp
Opis:
An analogy between a spin-glass and a material containing DX centers is postulated. The basis of the analogy is the formal identity of the Hamiltonians of these two systems. A correspondence between parameters of the spin-glass and of the DX system is established. Experiments which could support the above idea are proposed.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 620-622
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Erratum. Possible Long Time Tails in Current-Current Correlation Function for Two-Dimensional Electron Gas in Random Magnetic Field (Acta Phys. Pol. A 92, 1109 (1997))
Autorzy:
Łusakowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1968868.pdf
Data publikacji:
1998-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Źródło:
Acta Physica Polonica A; 1998, 93, 3; 563
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Free Carrier Concentration Dependence of Gd-Gd Exchange Constant in SnTe:Gd
Autorzy:
Łusakowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1934066.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Hx
75.30.Et
71.70.Gm
Opis:
In some samples of SnTe:Gd the measured paramagnetic Curie temperature strongly depends on the Fermi level position. The semi-quantitative theory which explains this effect is presented. The theory is based on Kasuya's model of exchange interaction between two 4f spins of rare earth ions. In this model the interaction between 4f electrons and the valence band goes via Gd atomic 5d orbitals which, contrary to the 4f orbitals are much more extended in space. The exchange integral and the paramagnetic Curie temperature dependence on the Fermi level position are calculated.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 1018-1022
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Distance Dependence of the Mn-Mn Exchange Interaction in IV-VI Semimagnetic Semiconductors
Autorzy:
Łusakowski, A.
Górska, M.
Powiązania:
https://bibliotekanauki.pl/articles/2036858.pdf
Data publikacji:
2003-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Gm
75.30.Hx
Opis:
In the present paper we calculate the exchange interaction between two manganese ions in IV-VI semiconductors with the rocksalt structure. The method of calculations is based on the fourth order perturbation theory with respect to hybridization between band states and localized d orbitals of Mn ions. This hybridization is described by three Harrison integrals: V$\text{}_{pdσ}$,V$\text{}_{pdπ}$, and V$\text{}_{sdσ}$. The band states of IV-VI semiconductor are obtained from the semiempirical tight binding model built from s and p orbitals of cations and anions. The resulting exchange term in the Hamiltonian is of the form -Σ$\text{}_{i,j=xyz}$J$\text{}_{ ij}$Ŝ$\text{}_{i}^{1}$Ŝ$\text{}_{j}^{2}$, however nondiagonal terms of the exchange integral tensor J$\text{}_{i≠j}$ are very small. The dependence of J$\text{}_{ij}$ on the Mn-Mn distance is non-monotonic. We also discuss the influence of the local crystal deformations on the exchange integral.
Źródło:
Acta Physica Polonica A; 2003, 103, 6; 659-664
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Anisotropy in GeMnTe - ab initio Calculations
Autorzy:
Łusakowski, A.
Bogusławski, P.
Powiązania:
https://bibliotekanauki.pl/articles/1376168.pdf
Data publikacji:
2014-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Gw
71.15.Mb
Opis:
Density functional theory calculations of the energy of magnetic anisotropy in GeMnTe were performed using OpenMX package with fully relativistic pseudopotentials. The discussion of microscopic origin of magnetic anisotropy was conducted. The main conclusion is that the magnetic anisotropy is caused by interplaty between spin-orbit and Coulomb interactions. The discussion includes also the influence of the free carriers concentration on the amplitude of energy of magnetic anisotropy. The important role of the chemical disorder is also pointed out.
Źródło:
Acta Physica Polonica A; 2014, 126, 5; 1177-1179
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of Chemical Disorder in $Pb_{1-x}Ge_{x}Te$
Autorzy:
Radzyński, T.
Łusakowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1811977.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.A-
61.43.-j
61.43.Bn
Opis:
The PbGeTe crystal lattice is locally deformed due to different ionic radii of cations and their random placement in the lattice. It is important to quantitatively characterize such microscopic disorder because local deformations have significant influence on the properties of magnetic ions introduced to such crystal. The simples method to study microscopic disorder is to consider purely classical model of the lattice in which neighboring atoms are connected by springs with properly chosen spring constant and equilibrium lengths. In the present work, using ab initio methods we discuss applicability of the springs-atoms model to the real crystal. We also explain results of extended X-ray absorption fine structure experiments performed on PbGeTe mixed crystals.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1317-1322
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Spin-Orbit Interaction on Band Structure and Elastic Properties of PbTe
Autorzy:
Radzyński, T.
Łusakowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1791363.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.A-
31.15.aj
71.20.-b
87.19.rd
Opis:
Inclusion of spin-orbit interaction in density functional theory calculations of PbTe band structure leads to wrong results concerning the symmetry of valence and conduction band wave functions. Using two ab initio codes: OpenMX and Quantum Espresso we show that changing the spin-orbit coupling strength in pseudopotentials for Pb it is possible to obtain proper energy gap and wave functions of proper symmetries.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 954-955
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Possible Long Time Tails in Current-Current Correlation Function for Two-Dimensional Electron Gas in Random Magnetic Field
Autorzy:
Łusakowski, A.
Turski, Ł. A.
Powiązania:
https://bibliotekanauki.pl/articles/1968462.pdf
Data publikacji:
1997-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.60.+w
72.10.-d
Opis:
We consider a two-dimensional degenerate electron gas in the presence of perpendicular random magnetic field. The magnetic field disorder which is assumed to be Gaussian is characterized by two parameters. The first is proportional to the amplitude of local magnetic field fluctuations. The second one characterizes the disorder on the longer scale - we call it the screening length. Using the Kubo formula for the conductivity we have found a class of diagrams which leads to the long time tails in the current-current correlation function. For short times in comparison with the diffusion time corresponding to the screening length this function behaves like logarithm of time, for longer times it decays like t$\text{}^{-1}$ which of course brings into question the diffusive character of the behavior of the charged particle in random magnetic field widely assumed in the literature.
Źródło:
Acta Physica Polonica A; 1997, 92, 6; 1109-1115
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Possible Origin of Large Value of Magnetic Anisotropy Constant in PbSnMnTe Mixed Crystals
Autorzy:
Łusakowski, A.
Story, T.
Gałązka, R. R.
Powiązania:
https://bibliotekanauki.pl/articles/1929772.pdf
Data publikacji:
1993-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Gw
Opis:
In PbSnMnTe crystals with the concentration of conducting holes of the order of 10$\text{}^{21}$ cm$\text{}^{-3}$, 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.
Źródło:
Acta Physica Polonica A; 1993, 84, 4; 829-831
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Anisotropy in (Ge,Mn)Te Layers
Autorzy:
Knoff, W.
Łusakowski, A.
Wołoś, A.
Story, T.
Powiązania:
https://bibliotekanauki.pl/articles/1386196.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.30.Gw
76.50.+g
Opis:
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.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 404-406
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation between Magnetic and Electronic Properties of Sn$\text{}_{1-x}$Gd$\text{}_{x}$Te
Autorzy:
Łusakowski, A.
Górska, M.
Arciszewska, A.
Grodzicka, E.
Gołacki, Z.
Story, T.
Powiązania:
https://bibliotekanauki.pl/articles/1931955.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Ck
75.30.Et
Opis:
Magnetic susceptibility, electron paramagnetic resonance and transport properties of Sn$\text{}_{1-x}$Gd$\text{}_{x}$Te with 0.04 < x < 0.07 and hole concentrations in the range from 0.7 × 10$\text{}^{20}$ to 16 × 10$\text{}^{20}$ cm$\text{}^{-3}$ were investigated. After annealing of the Sn$\text{}_{1-x}$Gd$\text{}_{x}$Te samples with x < 0.05 in Sn vapor their hole concentration decreased from 5 × 10$\text{}^{20}$ cm$\text{}^{-3}$ to about 3 × 10$\text{}^{20}$ cm$\text{}^{-3}$ and their paramagnetic Curie temperature increased a few times. In samples with x > 0.05 no significant change in the magnetic properties was observed after annealing, even at lower hole concentrations. The results can be explained by assuming that an indirect exchange interaction, 4f-5d-band electrons, is responsible for the coupling among Gd ions.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 197-200
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Specific Heat of Pb$\text{}_{1-x}$Eu$\text{}_{x}$Te
Autorzy:
Górska, M.
Łusakowski, A.
Jędrzejczak, A.
Gołacki, Z.
Anderson, J. R.
Balci, H.
Powiązania:
https://bibliotekanauki.pl/articles/2038143.pdf
Data publikacji:
2004-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.-d
75.40.Cx
Opis:
The temperature dependence of the magnetic specific heat was studied experimentally and theoretically in the semimagnetic semiconductor Pb$\text{}_{1-x}$Eu$\text{}_{x}$Te for x=0.027 and x=0.073, over the temperature range from 0.5 K to 15 K, in magnetic fields up to 2 T. In zero magnetic field at about 2 K there was a broad maximum in the magnetic specific heat, which was much higher than that predicted by the model of superexchange interaction between nearest neighbors; the maximum values increased with magnetic field. The experimental data were analyzed in the framework of a model which takes into account the spin splitting of the ground state of a single Eu2+ ion in the presence of local lattice distortions in the Pb$\text{}_{1-x}$Eu$\text{}_{x}$Te mixed crystal. The model describes well the experimental data, especially for lower x-values, where the contribution from singlets dominates.
Źródło:
Acta Physica Polonica A; 2004, 105, 6; 631-636
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Raman Spectroscopy of Co-Doped ZnO Bulk Crystals
Autorzy:
Szuszkiewicz, W.
Morhange, J. F.
Gołacki, Z.
Łusakowski, A.
Schumm, M.
Geurts, J.
Powiązania:
https://bibliotekanauki.pl/articles/2047700.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
78.30.Fs
Opis:
Low-temperature Raman spectra of a bulk mixed crystal Zn$\text{}_{1-x}$Co$\text{}_{x}$O (x = 0.016) are shown and analyzed. Besides the common modes of the ZnO host lattice, electronic transitions related to the presence of Co$\text{}^{2+}$ ions at the Zn sites are observed. In spite of the low Co concentration the presence of collective excitations corresponding to Co and CoO precipitates is also revealed.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 363-368
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High Field Magnetization of Sn$\text{}_{1-x}$Gd$\text{}_{x}$Te
Autorzy:
Górska, M.
Anderson, J. R.
Wolters, C.
Łusakowski, A.
Story, T.
Gołacki, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1969093.pdf
Data publikacji:
1998-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Ck
75.30.Et
Opis:
The magnetization of p-type Sn$\text{}_{1-x}$Gd$\text{}_{x}$Te with x up to 0.045 and the hole concentration, p, varying from 2.7 to 8.3×10$\text{}^{20}$ cm$\text{}^{-3}$ has been measured in magnetic fields up to 27 T, at the temperatures 4.2 and 1.3 K. The data were fitted to a magnetization equation with single-ion and pair terms. From comparison of the exchange parameters determined from the high-field magnetization with those previously obtained from the high-temperature magnetic susceptibility it was found that in samples with p>5×10$\text{}^{20}$ cm$\text{}^{-3}$ the exchange was of a short-range type, while in samples with a lower carrier concentration the long-range exchange mechanism was observed.
Źródło:
Acta Physica Polonica A; 1998, 94, 2; 347-350
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low-Frequency Raman Spectrum οf Bulk $Zn_{0.984}Co_{0.016}O$ Crystal
Autorzy:
Szuszkiewicz, W.
Łusakowski, A.
Morhange, J.
Gołacki, Z.
Arciszewska, M.
Brodowska, B.
Kanehisa, M.
Klepka, M.
Dobrowolski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1807848.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
78.30.Fs
Opis:
The influence of possible presence of $Co^{2+}$ ion pairs in a bulk $Zn_{1-x}Co_{x}O$ mixed crystal on the low-frequency part of the Raman spectrum is discussed. Two effects can be taken into account in the theoretical considerations when analyzing the energy level scheme corresponding to Co ions. The first is a local lattice deformation in the vicinity of $Co^{2+}$ ion due to a presence of the second ion, smaller than the host ZnO lattice cation. Such deformation creates a trigonal field, which can only slightly modify the energy levels of $Co^{2+}$ ion. The second effect, which results from an antiferromagnetic superexchange interaction between two $Co^{2+}$ ions is responsible for a new set of energy levels. The Raman data taken at low temperature on the sample corresponding to the composition x = 0.016 demonstrated the presence of two structures at about 6 $cm^{-1}$ and 13 $cm^{-1}$. These structures may be interpreted as electronic transitions between the ground state and the first excited state of a single $Co^{2+}$ ion in the substitution site of ZnO lattice and as a similar transition for $Co^{2+}$ ion pair, respectively.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 103-106
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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