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Tytuł:
The Nonlinear Diffusion Equation Describing Spread of Impurities of High Density
Autorzy:
Janavičius, A. J.
Lūža, G.
Jurgaitis, D.
Powiązania:
https://bibliotekanauki.pl/articles/2038073.pdf
Data publikacji:
2004-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
Opis:
The nonlinear diffusion equation is derived by taking into account the local variations in the solvent density, within a mechanism of diffusion driven by random particle collisions. Analytical solutions for the case of spherical-symmetric nonlinear diffusion equation for spread of impurities in gas and solids are obtained and discussed. In this case, the solutions of the nonlinear diffusion equation are similar to solutions of Bernoulli equation. We note that the obtained solutions can be used to describe the shapes of impurity gas of high concentration or smoke clouds.
Źródło:
Acta Physica Polonica A; 2004, 105, 5; 475-483
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analytical Solution of Nonlinear Diffusion Equation in Two-Dimensional Surface
Autorzy:
Janavičius, A. J.
Turskienė, S.
Powiązania:
https://bibliotekanauki.pl/articles/2044566.pdf
Data publikacji:
2005-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
Opis:
We considered practically important case of nonlinear diffusion in the anisotropic plane where diffusion coefficients for diffusion in x and y axis directions can be different. This equation was transformed using similarity variables. The approximate analytical solution of the transformed equation expressed by power-series expansion for two variables about the zero point including only the first terms. The graphic representations show sufficient accuracy of the obtained analytical solution.
Źródło:
Acta Physica Polonica A; 2005, 108, 6; 979-983
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metal-Insulator Transition in Doped Semiconductors
Autorzy:
Jaroszyński, J.
Powiązania:
https://bibliotekanauki.pl/articles/1888088.pdf
Data publikacji:
1991-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
Opis:
A survey is given of different kinds of metal-insulator transitions (MIT) in doped semiconductors. The role of electron-electron Coulomb interactions and of disorder is discussed vis-a-vis millikelvin experimental results for semimagnetic semiconductors (SMSC) in the vicinity of MIT. Critical behavior of conductivity tensor components and dielectric susceptibility at the magnetic field-induced MIT in p-type Hg$\text{}_{1-x}$Mn$\text{}_{x}$Te is compatible with the model in which the MIT is a result of quantum localization driven by disorder-modified electron-electron interactions. At the same time the critical behavior of the Hall coefficient suggests that, in addition to electrons forming the Fermi liquid (FL) and undergoing localization at the MIT, there is certain a concentration of local electron moments, even on the metallic side of the MIT. The formation of these moments can presumably be described in terms of a disordered Hubbard-Mott model.
Źródło:
Acta Physica Polonica A; 1991, 80, 2; 255-265
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Mechanism of Excitation Energy Transfer Involving Long and Short Range Interaction in Dilute Organic Liquid Scintillator Systems
Autorzy:
Hanagodimath, S. M.
Gadaginamath, G. S.
Chikikur, G. C.
Powiązania:
https://bibliotekanauki.pl/articles/1920488.pdf
Data publikacji:
1992-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
34.30.+h
Opis:
The rate parameter K$\text{}_{3}$ of solvent-solute energy transfer and the rate parameter K$\text{}_{7b}$ for solvent-quencher energy transfer are determined experimentally under ultraviolet excitation for a system Ethyl 1 butyl-2-methyl-5 ethoxycarboxy methoxy indole-3-carboxylate (EBMEC) in a deoxygenated system comprising 1:9 mixture of toluene-cyclohexane as a function of temperature in the range of 20-70°C, using bromobenzene as a solvent quencher. The data is analysed in terms of compact equation formed by combining Voltz et al. and Birks and Conte models. The interaction distance for the energy transfer from the excited solvent to solute molecules and solvent to quencher molecules are determined using this equation. The magnitude of the interaction distance indicates that the excitation energy transfer takes place due to long-range interaction in the case of solvent-solute energy transfer and short-range interaction in the case of solvent quencher energy transfer in dilute systems.
Źródło:
Acta Physica Polonica A; 1992, 81, 3; 361-368
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analytical Solution of Nonlinear Diffusion Equation Describing Interdiffusion of Gases
Autorzy:
Janavičius, A.
Jurgaitis, D.
Powiązania:
https://bibliotekanauki.pl/articles/1585041.pdf
Data publikacji:
2009-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
Opis:
The diffusion is the result of Brownian movement and occurs with a finite velocity. We consider the nonlinear diffusion equation, with diffusion coefficient directly proportional to the impurities concentration. In this case of diffusion from the constant source, the maximum displacements of diffusing particles are proportional to the square root of diffusion time. This result coincides with Brownian movement theory. The obtained analytically solutions were successfully applied for describing the diffusion and superdiffusion experiments' in solids. After theoretical consideration of application of this equation for diffusion in gases, we are investigating here the binary nonlinear diffusion in gases. We obtained the nonlinear interdiffusion equation, for the spherical symmetric case, and presented the approximate analytical solutions.
Źródło:
Acta Physica Polonica A; 2009, 116, 6; 1025-1028
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Nonlinear Diffusion in the Nonisothermical Case
Autorzy:
Janavičius, A. J.
Powiązania:
https://bibliotekanauki.pl/articles/1968857.pdf
Data publikacji:
1998-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
Opis:
We will discuss the properties of the nonlinear equation in the nonisothermical case. In our previous papers the diffusion coefficient directly proportional to the concentration of the impurities was proposed and it was exactly defined. Now the nonlinear diffusion equation is solved for the temperature and for the diffusion coefficient depending on time in a special way. The temperature function T(t) has the singularity at the free chosen time moment t$\text{}_{0}$. The obtained analytical solutions define the diffusion profiles for increasing temperatures and in the case of excited systems when the vacancies and the impurity's atoms are not in the thermal equilibrium with lattice. Considering the connection between temperature function and the population of excited states for atoms surrounding vacancies the possibility of the superdiffusion is shown.
Źródło:
Acta Physica Polonica A; 1998, 93, 3; 505-512
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear Many-Staged Diffusion
Autorzy:
Janavičius, A.
Powiązania:
https://bibliotekanauki.pl/articles/1968915.pdf
Data publikacji:
1998-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
Opis:
We considered and solved the nonlinear diffusion equation formerly. The more complicated but more useful task of many-staged diffusion is solved in this paper. The obtained solution satisfies the initial distribution of the impurities and can be generalized for many-staged diffusion. Using these solutions we can take into account all the stages of a planary transistor formation.
Źródło:
Acta Physica Polonica A; 1998, 93, 5-6; 731-735
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear Diffusion Equation with Diffusion Coefficient Directly Proportional to Concentration of Impurities
Autorzy:
Janavičius, A. J.
Poškus, A.
Powiązania:
https://bibliotekanauki.pl/articles/2042120.pdf
Data publikacji:
2005-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
Opis:
We analyzed a diffusion model based on the assumption that the sufficient condition for the mass flux at point x+L to be different from zero is a nonzero value of the impurity gradient and of impurity concentration at point x. In our model, the length of the jump of diffusing particles from one equilibrium position to another has a defined value L. By describing variation of impurity concentration with time when the frequency of the jumps depends on coordinates and L, the nonlinear diffusion equation was derived. We found that the diffusion coefficient in this nonlinear equation is directly proportional to the concentration of impurities, as it had been proposed in earliest papers. The derived nonlinear diffusion equation was solved numerically for the case of spherical symmetry.
Źródło:
Acta Physica Polonica A; 2005, 107, 3; 519-524
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Global Structure of the Falicov-Kimball Model Ground State Phase Diagram
Autorzy:
Lach, J.
Łyżwa, R.
Jędrzejewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1929588.pdf
Data publikacji:
1993-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Mb
71.30.+h
Opis:
The two-state spinless Falicov-Kimball model on a one-dimensional lattice is studied by means of well-controlled numerical procedures. Restricted phase diagrams in the grand-canonical ensemble and at zero temperature are constructed. The evolution of these phase diagrams, as the interaction parameter U is varied, including the band structures corresponding to configurations of localized particles (ions) and densities of mobile particles (electrons), is monitored. The changes observed enable us to draw conclusions for the global structure of the phase diagram and to make a qualitative plot of such a diagram. Particular attention is paid to the possibility of conductor-insulator transitions. The results obtained suggest that the system is an insulator for all U only if the electron and ion densities ρ$\text{}_{e}$,ρ$\text{}_{i}$ satisfy the conditions: ρ$\text{}_{e}$ + ρ$\text{}_{i}$ = 1, |ρ$\text{}_{i}$ - 1/2| ≤ δ < 1/2. For all other pairs (ρ$\text{}_{e}$,ρ$\text{}_{i}$) there is a critical U at which the system undergoes a conductor-insulator transition.
Źródło:
Acta Physica Polonica A; 1993, 84, 2; 327-344
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pretransition Phenomena in Fast-Proton Conductors
Autorzy:
Waplak, S.
Bednarski, W.
Ostrowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/2043554.pdf
Data publikacji:
2005-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.-v
66.30.-h
Opis:
In this paper we present recent experimental results related to nonlinear crystal field fluctuations and current flow in K$\text{}_{3}$H(SO$\text{}_{4}$)$\text{}_{2}$ fast-proton conductor far below the transition temperature T$\text{}_{g}$. The results for crystalline and powdered samples are quantitatively explained in the framework of soliton model of charge transport.
Źródło:
Acta Physica Polonica A; 2005, 108, 2; 261-270
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared Reflection of $MnTe_2$ under High Pressure
Autorzy:
Mita, Y.
Ishida, Y.
Kobayashi, M.
Endo, S.
Powiązania:
https://bibliotekanauki.pl/articles/1813955.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
78.30.-j
Opis:
The IR reflection measurements of $MnTe_2$ were performed at room temperature under various pressures. It is observed that the reflectivity increases at the pressure range of 8-25 GPa and becomes almost constant at the higher pressure. The carrier concentrations obtained from the reflectivity spectra at the highest pressure region are the order of $10^{22} cm^{-3}$. Therefore it is concluded that pressure-induced semiconductor-metal transition occurs at the pressure range of 8-25 GPa.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 617-620
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation-Driven Metal-Insulator Transitions
Autorzy:
Honig, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/2011236.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.45.Gm
Opis:
The effect of correlation-driven electronic transitions are described for the V$\text{}_{2}$O$\text{}_{3}$, NiS$\text{}_{2-x}$Se$\text{}_{x}$, and Fe$\text{}_{3}$O$\text{}_{4}$ systems. The various tranformations can all be rationalized in terms of elementary concepts pertaining to the Mott-Hubbard intraatomic electronic interactions or in terms of an order-disorder formalism involving Coulomb interactions among electrons on adjacent sites. Attention is directed to some outstanding issues that require further resolution.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 141-156
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation between Magnetic Phases and Insulator-Metal Transition in La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ Perovskite
Autorzy:
Baszyński, J.
Idzikowski, B.
Toliński, T.
Hoser, A.
Powiązania:
https://bibliotekanauki.pl/articles/2013369.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
75.25.+z
Opis:
The La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ ceramic perovskites are investigated using the neutron diffraction technique and resistance measurements in the temperature range from 260 K down to 5 K. We have found that the integrated intensity of the antiferromagnetic peaks was growing with decreasing temperature and reached the maximum at a temperature about 20 K lower than that of the semiconductor-metal transition and did not vanish at 5 K. The semiconductor-metal transition is correlated with the temperature of the maximum of the lattice c-parameter and the percolation of ferromagnetic domains. Our results suggest that although the ferromagnetic long-range order is established through the semiconductor-metal transition induced percolation network, locally the antiferromagnetic correlation can remain.zapisz
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 779-782
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neutron Diffraction Study of Ferromagnetic Ordering in La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ Induced by Electric Field
Autorzy:
Baszyński, J.
Idzikowski, B.
Toliński, T.
Hoser, A.
Powiązania:
https://bibliotekanauki.pl/articles/2013692.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
75.25.+z
Opis:
We used the neutron diffraction technique to study the ferromagnetic ordering process in La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ induced by the short impulse of the external electric field E=4 V/cm at a magnetic field H=1.5 T. Our sample was prepared by the standard solid-state reaction. The diffraction measurements at 4 K, carried out for the neutron wavelength λ=0.2442 nm, have revealed the orthorhombic perovskite structure with the unit-cell parameters: a=0.5480 nm, b=0.5550 nm and c=0.7737 nm. We observed that a short impulse of the electric field develops the ferromagnetic ordering in a similar way as the magnetic field up to 4 T. We assume that the increased ferromagnetic ordering induced by the external electric field at a given magnetic field has the same physical origin as in the case of the Zener double exchange. The effect is confirmed by magnetic moment measurements using vibrating sample magnetometer.
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 831-834
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Radioactivity investigation of sediment samples from Beni Haroun Dam using high-resolution gamma-ray spectroscopy
Autorzy:
Bouhila, G.
Benrachi, F.
Powiązania:
https://bibliotekanauki.pl/articles/1050951.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
29.90.+r
29.30.-h
Opis:
In this study, the levels of natural and anthropogenic radioactivity in the sediment samples, collected from Beni Haroun Dam, were investigated using gamma-ray spectrometry. The results obtained for the ²³⁸U, ²³²Th series, ⁴⁰K natural element and ¹³⁷Cs anthropogenic radionuclide are discussed. To evaluate the radiological hazard of radioactivity in samples, the absorbed dose rate, the annual effective dose, the radium equivalent activity Ra_{eq}, the external and internal hazard indices H_{ex} and H_{in} were calculated and presented in comparison with the data collected from different areas in the world.
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 889-891
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessments of natural radioactivity concentration and radiological hazard indices in surface soils from the Gözlek Thermal SPA (Amasya-Turkey)
Autorzy:
Bolat, B.
Öner, F.
Çetın, B.
Powiązania:
https://bibliotekanauki.pl/articles/1054952.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
29.90.+r
29.30.-h
Opis:
The concentration of natural radioactivity was determined in the surface soil of the Gözlek Thermal SPA in Amasya. The activity concentrations of natural radionuclides in soil samples were determined using gamma-ray spectrometer, containing a 3"× 3" NaI(Tl) detector connected to multi-channel-analyser. The photo-peaks at 1460, 1764 and 2615 keV are due to ⁴⁰K, ²²⁶Ra and ²³²Th, respectively. The radiological hazard indices of the natural radionuclides content, radium equivalent activities Ra_{eq}, absorbed dose rate (ADR), annual effective dose rate (AEDR) and external hazard index H_{ex} were also calculated.
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 1200-1202
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Distribution of Natural Radioactivity from $\text{}^{40}K$ Radioelement in Volcanics of Sandıklı-Şuhut (Afyon) Area
Autorzy:
Uyanik, N.
Öncü, Z.
Uyanik, O.
Bozcu, M.
Akkurt, İ.
Günoğlu, K.
Yağmurlu, F.
Powiązania:
https://bibliotekanauki.pl/articles/1402499.pdf
Data publikacji:
2015-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
93.85.-q
29.30.-h
Opis:
Many radioactive elements have existed when the Earth had appeared and the long living of them are still present. One of the most important of these radioactive elements is $\text{}^{40}K$. It makes about 0.012% of total content of K, widely represented in many different rocks. In this study the distribution of the natural $\text{}^{40}K$ radioelement in the volcanics of the south part of Afyon was investigated. Gamma-ray spectrometer was used for in-situ measurements of this radioelement concentration. Studied area has covered approximately 1800 km². In-situ measurements were performed at 1390 different locations in this field. Data for each measurement was gathered during 3 min. The map of the ^{40}K element distribution in the studied area was produced. The high values of $\text{}^{40}K$, according to this map, were obtained in the areas of the alteration zones, between Sandıklı and Şuhut in the studied area.
Źródło:
Acta Physica Polonica A; 2015, 128, 2B; B-438-B-440
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Diagram of Metal-Insulator Transition in System with Anderson-Hubbard Centers
Autorzy:
Skorenkyy, Yu.
Didukh, L.
Kramar, O.
Dovhopyaty, Yu.
Powiązania:
https://bibliotekanauki.pl/articles/1418528.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Lp
71.30.+h
Opis:
The model of a strongly correlated system in which periodically spaced Anderson-Hubbard centers are introduced into narrow-band metal is considered. Besides the interactions between localized magnetic moments and strong on-site Coulomb interaction, the model takes into account the hybridization of localized and band states. To study the effect of the lattice deformation on the electrical properties of the system, the phonon term and elastic energy have been taken into account. Green functions for band and localized electrons have been found. On this base, the energy spectrum has been investigated as a function of model parameters, temperature and external pressure. The criterion of the metal-insulator transition for an integer value of electron concentration has been derived and the phase diagram of the metal-insulator transition has been built.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 532-534
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conductivity Near the Metal-to-Insulator Transition in Cd$\text{}_{1-x}$Mn$\text{}_{x}$Se:Sc
Autorzy:
Głód, P.
Sawicki, M.
Lenard, A.
Dietl, T.
Plesiewicz, W.
Powiązania:
https://bibliotekanauki.pl/articles/1887158.pdf
Data publikacji:
1991-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.55.Jv
Opis:
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$\text{}_{0.95}$Mn$\text{}_{0.05}$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$\text{}_{1-x}$Mn$\text{}_{x}$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.
Źródło:
Acta Physica Polonica A; 1991, 79, 2-3; 389-392
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Investigation of the Cu Ions Diffusion into Bulk Lithium Niobate
Autorzy:
Sugak, D.
Syvorotka, I.
Yakhnevych, U.
Buryy, O.
Martynyuk, N.
Ubizskii, S.
Zhydachevskyy, Ya.
Suchocki, A.
Kumar, H.
Janyani, V.
Singh, G.
Powiązania:
https://bibliotekanauki.pl/articles/1030967.pdf
Data publikacji:
2018-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
78.20.-e
Opis:
Spatial changes of optical properties of bulk LiNbO₃ crystal were investigated after annealing in CuO powder. The incorporation of copper ions into the crystal was confirmed by registration of additional absorption spectra that revealed formation of the absorption bands of both Cu⁺ (400 nm) and Cu²⁺ (1000 nm) ions. The changes of optical absorption caused by thermal treatment were registered along the direction of diffusion by the probe beam perpendicular to this direction. The anisotropy of diffusion was revealed. The maxima were observed on the depth dependences of additional absorption both for the wavelengths of 400 and 1000 nm for all main crystallographic directions. The concentrations of copper ions were calculated in accordance with the Smakula-Dexter formula. The X-ray diffraction study revealed reflexes which probably belong to CuNb₂O₆, CuNbO₃ and CuO. The halo was observed on these diffraction patterns that confirms the formation of the scattering centers (about 1 nm in diameter) in the near-surface region.
Źródło:
Acta Physica Polonica A; 2018, 133, 4; 965-972
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Co Ions Diffusion in Gd₃Ga₅O₁₂ Single Crystals
Autorzy:
Sugak, D.
Syvorotka, I.
Yakhnevych, U.
Buryy, O.
Vakiv, M.
Ubizskii, S.
Włodarczyk, D.
Zhydachevskyy, Ya.
Pieniążek, A.
Jakiela, R.
Suchocki, A.
Powiązania:
https://bibliotekanauki.pl/articles/1030989.pdf
Data publikacji:
2018-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
78.20.-e
Opis:
Spatial changes of properties of Gd₃Ga₅O₁₂ (GGG) single crystals caused by diffusion of cobalt ions during high-temperature annealing (1200°C, 24 h) in Co₃O₄ powder are investigated. The registration of these changes was carried out by optical spectrophotometry, microscopy and micro-Raman scattering methods. Changes in structure of near-surface layers of the crystal were investigated by X-ray diffraction technique. It was shown that the additional absorption induced by annealing is related to intra-center optical transitions in Co²⁺ ions, which occupy tetrahedral positions in the garnet structure at the distances of 250-500 μm from the crystal surface. The dependence of induced absorption with depth has got a non-monotonous character with a maximum at 400 μm. A comparison of the results obtained by different methods allows to suppose that the thermal treatment of GGG in the presence of cobalt ions leads to formation of the structurally and chemically non-uniform layer with a width about 500 μm.
Źródło:
Acta Physica Polonica A; 2018, 133, 4; 959-964
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of natural radioactivity concentrations in surface soils in the Yeşilırmak river in Amasya, Turkey
Autorzy:
Çetin, B.
Powiązania:
https://bibliotekanauki.pl/articles/1065705.pdf
Data publikacji:
2016-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
29.90.+r
29.30.-h
Opis:
In this study, natural radioactivity concentration in the surface soils along the Yeşilırmak river in Amasya have been investigated. The activity concentrations of radionuclides of the ²²⁶Ra and ²³²Th decay chains and of the ⁴⁰K were determined by means of gamma-ray spectrometry measurements made using a 3 × 3'' NaI(Tl) detector system. Concerning radiological risk, the absorbed gamma dose in air from those soils and the outdoor annual effective dose equivalent were calculated.
Źródło:
Acta Physica Polonica A; 2016, 130, 1; 320-321
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of Natural Radioactivity from $\text{}^{232}Th$ with Gamma-Ray Spectrometer in Dereköy-Yazır (Southwestern Anatolia)
Autorzy:
Uyanik, N.
Öncü, Z.
Uyanik, O.
Akkurt, İ.
Powiązania:
https://bibliotekanauki.pl/articles/1402500.pdf
Data publikacji:
2015-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
92.20.Td
29.30.-h
Opis:
This study presents new data on the baseline concentrations of Thorium over the Dereköy-Yazır (Ağlasun-Burdur) volcanic area. Portable gamma-ray spectrometer was used for natural thorium mapping. In situ measurements were made in the field, in the area of 7.5 km² at 165 points. Variations in the Th concentration in the surficial environment of the Dereköy-Yazır region appear to be related to bedrock lithology. The measured thorium concentration varies between 0.68-36 ppm, in the studied area. The highest concentration values were obtained from volcanic rocks. The outcropping volcanic rocks in the region are Pliocene alkaline basalts.
Źródło:
Acta Physica Polonica A; 2015, 128, 2B; B-441-B-442
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superdiffusion in Si Crystal Lattice Irradiated by Soft X-Rays
Autorzy:
Janavičius, A.
Balakauskas, S.
Kazlauskienė, V.
Mekys, A.
Purlys, R.
Storasta, J.
Powiązania:
https://bibliotekanauki.pl/articles/1812042.pdf
Data publikacji:
2008-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
78.70.Ck
Opis:
We considered the reasons of superdiffusivity and measured profiles of boron and phosphorus in crystalline silicon at room temperature. The superdiffusivity or ultrafast diffusion of metastable vacancies at room temperature in Si crystal irradiated by soft X-rays was obtained experimentally. In this work, we presented experimentally obtained diffusion coefficients of singly and doubly negatively charged long-lived excited vacancies. These high concentration charged metastable vacancies (about $10^{13} cm^{-3}$) at room temperature can very fast diffuse changing electrical conductivity and the Hall mobility of carriers. We measured the superdiffusivity of negatively charged vacancies, generated by the Auger effect in the regions of the sample, which were not affected by X-rays. In this paper, we presented the obtained superdiffusion profiles of boron and phosphorus in crystalline silicon measured with secondary-ion mass spectrometer.
Źródło:
Acta Physica Polonica A; 2008, 114, 4; 779-790
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Quantum Effects in Carbonaceous Materials Near the Metal-Insulator Transition by Means of THz Photoconductivity
Autorzy:
Dorosinets, V.
Ksenevich, V.
Seliuta, D.
Martūnas, Z.
Valušis, G.
Powiązania:
https://bibliotekanauki.pl/articles/1813203.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.15.Rn
Opis:
A series of carbonaceous fibers with conductivity tuned to the metal-insulator transition were prepared by heat treatment of chemically modified polymer precursors. Peculiar behaviour of the resistivity versus temperature dependence R(T) at low temperatures suggests quantum corrections to the Drude conductivity due to weak localization and electron-electron interaction dominating in the conductivity. The THz conductivity method is employed to study the modification of the density of states and provides evidence for a strong change in density of states at the Fermi level caused by the quantum effects.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 875-878
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transport and Magnetic Studies of New Mixed-Valence Compounds: K$\text{}_{3}$Cu$\text{}_{8}$Se$\text{}_{6}$, KCu$\text{}_{3}$Se$\text{}_{2}$, K$\text{}_{3}$Cu$\text{}_{8}$Te$\text{}_{6}$ and BaCuS$\text{}_{3-x}$
Autorzy:
Jacyna-Onyszkiewicz, I.
Sidowski, M.
Starodub, W.
Ratuszna, A.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1955832.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.-g
71.30.+h
Opis:
New mixed-valent copper chalcogenides BaCuS$\text{}_{3-x}$ and K$\text{}_{3}$Cu$\text{}_{8}$X$\text{}_{6}$ with X=Se or Te and KCu$\text{}_{3}$Se$\text{}_{2}$, with chemical patterns corresponding to the recently investigated K$\text{}_{3}$Cu$\text{}_{8}$S$\text{}_{6}$ and KCu$\text{}_{3}$S$\text{}_{2}$, were synthesized. For these new samples the results of resistivity and magnetic susceptibility measurements are presented. For BaCuS$\text{}_{3-x}$, K$\text{}_{3}$Cu$\text{}_{8}$Se$\text{}_{6}$ and KCu$\text{}_{3}$Se$\text{}_{2}$ the metal-insulator transition is observed with the low temperature phase being metallic, which is untypical, whereas K$\text{}_{3}$Cu$\text{}_{8}$Te$\text{}_{6}$ is a metal in the investigated temperature range. The temperature dependence of magnetic susceptibility of the studied samples testifies to their diamagnetic or weakly paramagnetic behaviour.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 405-408
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic Properties of Mesoscopic Cylinder
Autorzy:
Zipper, E.
Stebelski, M.
Lisowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1968457.pdf
Data publikacji:
1997-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.10.-d
Opis:
The electromagnetic response of a mesoscopic cylinder made of a normal metal or a semiconductor is studied. The relation between the induced current J(q,w) and the electric field E(q,w) is derived. It is shown that the kernel K(q,w) which determines the properties of the system has a finite limit which implies infinite conductivity. The mesoscopic cylinder by virtue of its topology and small dimensions can support a persistent current. If the coherence of currents from different channels is strong enough a novel effect - the self-sustaining current can be obtained. We show that a mesoscopic multichannel system exhibits some features which bear resemblance to the superconductor.
Źródło:
Acta Physica Polonica A; 1997, 92, 5; 1087-1091
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Phase Transition in Layered Materials 1T-TaS$\text{}_{x}$Se$\text{}_{2-x}$ Probed by Cryogenic STM/STS
Autorzy:
Hasegawa, T.
Shiino, O.
Yamaguchi, W.
Endo, T.
Sugawara, H.
Kitazawa, K.
Powiązania:
https://bibliotekanauki.pl/articles/1968713.pdf
Data publikacji:
1998-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.20.-b
Opis:
A metal-insulator transition, Mott transition, in layered materials 1T-TaS$\text{}_{x}$Se$\text{}_{2-x}$ was investigated by cryogenic scanning tunneling microscopy/ spectroscopy. At 77 K, tunneling spectra in the insulating phase showed a conduction band with almost half filling, which becomes narrower as x decreases. Around the transition point x≈1.4 at 77 K, we observed a sign of gap opening without an overshooting peak at zero bias, supporting the Mott localization picture in which a carrier number vanishes at the transition point. From the site-specified scanning tunneling spectroscopy measurements, furthermore, electrons were found to localize at the charge density wave crest positions. In 1T-TaS$\text{}_{2}$, we have also found that both metallic and insulating phases coexist in a nanometer scale just above the transition temperature, 180 K. >From the minimum size of the insulating region, the coherence length of Mott insulating state was evaluated to be≈5 nm.
Źródło:
Acta Physica Polonica A; 1998, 93, 2; 297-305
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling of Thermodiffusion Inertia in Metal Films Heated with Ultrashort Laser Pulses
Autorzy:
Janavičius, A. J.
Turskienė, S.
Powiązania:
https://bibliotekanauki.pl/articles/2047101.pdf
Data publikacji:
2006-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
79.20.Ds
Opis:
Previously, we considered the analytical solution of nonlinear diffusion equation in two-dimensional surface. This allows us to consider the same nonlinear heat conduction equation for metals heated by a picosecond laser. After fast thermalization (within a few femtoseconds) of the laser energy and electron excitation in the conductivity band, electrons ballistically diffuse and transfer their energies to the target atoms and equilibrium electrons from the conductivity band. In this case, we have thermal diffusion of nonequilibrium excited electrons and thermal inertia for thermodiffusion. The relaxation time of excited conductivity electrons is directly connected with thermal inertia and depends on electron-electron collision frequencies. The theoretical temperature surface plots for the thermodiffusion of excited electrons were obtained from analytical solutions of nonlinear thermodiffusion equations.
Źródło:
Acta Physica Polonica A; 2006, 110, 4; 511-521
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some Electronic Properties of Sr$\text{}_{1-x}$A$\text{}_{x}$CuO$\text{}_{2+δ}$ where A=La, K, and Ca
Autorzy:
Onyszkiewicz, I.
Czarnecki, P.
Poltoracky, Yu. B.
Zimpel, M.
Powiązania:
https://bibliotekanauki.pl/articles/1929860.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.15.-v
76.30.Fc
Opis:
The electronic properties of Sr$\text{}_{1-x}$A$\text{}_{x}$CuO$\text{}_{2+δ}$ (A = La, K, Ca) were examined. The crystal structure of the synthesized compounds was identified as orthorhombic with some admixture of tetragonal phase. For Sr$\text{}_{1-x}$La$\text{}_{x}$CuO$\text{}_{2+δ}$ the insulator-metal like transition was observed with increasing La content. The d$\text{}_{x²-y²}$ ground state of Cu ions was deduced from electron spin resonance measurements. The electronic state of Cu ions and their surrounding local symmetry was also found to be La and oxygen content dependent.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 303-306
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies of the Magnetic Axis Switching in Magnetite
Autorzy:
Król, G.
Kusz, J.
Tarnawski, Z.
Kąkol, Z.
Tabiś, W.
Kozłowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/2046773.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
61.50.Ks
75.30.Gw
Opis:
The influence of the external magnetic field on magnetic and crystallographic structure of magnetite was studied. We have confirmed, by means of vibrating sample magnetometer measurements, that external magnetic field can switch the easy magnetic axis to the new crystallographic direction. We have also proved by the direct observation of the crystalline structure that this phenomenon is strictly related to the crystallographic structure relaxation.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 601-605
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metal-Insulator Transition in Zinc-Doped LaSrCuO
Autorzy:
Malinowski, A.
Cieplak, M. Z.
Berkowski, M.
Plesiewicz, W.
Skośkiewicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/2046782.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.-h
71.30.+h
74.25.Fy
Opis:
The magnetotransport in the vicinity of the metal-insulator transition in La$\text{}_{1.85}$Sr$\text{}_{0.15}$Cu$\text{}_{x}$Zn$\text{}_{1-x}$O$\text{}_{4}$ 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$\text{}_{2-x}$Sr$\text{}_{x}$CuO$\text{}_{4}$. 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.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 617-621
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of Environmental Risk from Coal Using Neutron Activation Analysis
Autorzy:
Ileri, R.
Hacıyakupoğlu, S.
Esen, A.
Oruçığlu, E.
Erentürk, S.
Powiązania:
https://bibliotekanauki.pl/articles/1401232.pdf
Data publikacji:
2015-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
29.30.-h
89.30.ag
07.88.+y
Opis:
This study aimed to determine element concentration in coal samples and to assess Co, Cr, Se, Th and U leaching from coals exposed to a simulated coal cleaning process. Coal samples taken from a local area of Turkey were grounded and exposed to water for one month period. Then the cleaned samples were filtered and dried. The elemental concentrations in the samples before and after the cleaning procedure were determined by relative neutron activation analysis (NAA). Raw and water cleaned coal samples were irradiated in central irradiation tube of TRIGA MARK II Research Reactor at 250 kW for 6 h and measured for their activities by using high resolution gamma spectroscopy system. The results showed that leaching percentage for Se is up to 100% and for Co, Cr, Th and U up to 71%, 17%, 30%, 28% respectively.
Źródło:
Acta Physica Polonica A; 2015, 127, 4; 1010-1012
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear Diffusion in Excited HgCdTe and Si Crystals
Autorzy:
Janavičius, A. J.
Norgėla, Ž.
Purlys, R.
Powiązania:
https://bibliotekanauki.pl/articles/2036987.pdf
Data publikacji:
2003-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
66.30.Hs
78.70.Ck
Opis:
We discuss the properties of the nonlinear diffusion equation for the case of diffusion in excited systems. The diffusion coefficient is directly proportional to the concentration of impurities and depends on time in a special way. For the description of the excited systems, we used a special temperature function, which defined the time dependent diffusion coefficient and the Boltzmann distribution of the excited vacancies or impurity atoms in solids. This model was used for the approximation of indium concentration profiles in HgCdTe of a rapid diffusion component and very fast diffusion of metastable vacancies irradiated by soft X-rays in an excited Si crystal.
Źródło:
Acta Physica Polonica A; 2003, 104, 5; 459-467
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fast Diffusion of Metastable Vacancies in Surface of Excited Si Crystals
Autorzy:
Janavičius, A. J.
Turskienė, S.
Powiązania:
https://bibliotekanauki.pl/articles/2047100.pdf
Data publikacji:
2006-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
66.30.-h
66.30.Hs
78.70.Ck
Opis:
We considered the practically interesting, very fast nonlinear diffusion of metastable vacancies in the surface of Si crystal, excited by soft X-rays. Here we used experimentally defined diffusion coefficients of singly and doubly negatively charged very fast vacancies generated by soft X-rays. These high concentration (about 10$\text{}^{13}$ cm$\text{}^{-3}$) metastable vacancies at room temperature can diffuse and exist in the crystal for a very long time (about 24 hours for not so fast neutral vacancies) changing electrical conductivity, the Hall mobility of carriers and generating some resonance phenomena in the lattice of Si crystal. We measured superdiffusivity of negatively charged vacancies, generated by the Auger effect in the regions of the sample, where X-rays did not acted. In the paper we modified the formerly obtained analytical solution of nonlinear diffusion equation for calculation of distribution of vacancies in two-dimensional surface.
Źródło:
Acta Physica Polonica A; 2006, 110, 4; 505-510
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetoresistive Properties of Manganite-Based Heterojunctions
Autorzy:
Devenson, J.
Vengalis, B.
Lisauskas, V.
Oginskis, A.
Anisimovas, F.
Ašmontas, S.
Powiązania:
https://bibliotekanauki.pl/articles/1807945.pdf
Data publikacji:
2009-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.70.-i
71.30.+h
73.50.-h
Opis:
Hole-doped $La_{2/3}Ba_{1/3}MnO_{3}$ (LBaMO), $La_{2/3}Ca_{1/3}MnO_{3}$ (LCaMO) and $La_{2/3}Ce_{1/3}MnO_{3}$ (LCeMO) thin films were grown heteroepitaxially on 0.1 wt.% Nb-doped $SrTiO_{3}(100)$ (STON) substrates by magnetron sputtering. The prepared LBaMO/STON, LCaMO/STON, LCeMO/STON heterostructures demonstrated nonlinear rectifying current-voltage characteristics. Negative magnetorestance values have been indicated at low bias, meanwhile bias-dependent magnetoresistance has been measured at positive bias voltage values U > U_d where U_d is the interfacial potential, corresponding to a steep current increase at a forward bias.
Źródło:
Acta Physica Polonica A; 2009, 115, 6; 1130-1132
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Possibility of Spontaneous Currents in Mesoscopic Systems
Autorzy:
Zipper, E.
Szopa, M.
Wohlleben, D.
Freche, P.
Esser, M.
Powiązania:
https://bibliotekanauki.pl/articles/1929407.pdf
Data publikacji:
1993-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.10.-d
71.10.+x
Opis:
It is shown that a mesoscopic metallic system can exhibit a phase transition to a low temperature state with a spontaneous orbital current if it is sufficiently free of elastic defect scattering. The interaction among the electrons, which is the reason of the phase transition, is of the magnetic origin and it leads to an ordered state of the orbital magnetic moments.
Źródło:
Acta Physica Polonica A; 1993, 84, 1; 203-211
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Light-Controlled Transport in Doped Diluted Magnetic Semiconductors near Localization Boundary
Autorzy:
Głód, P.
Dietl, T.
Wojtowicz, T.
Sawicki, M.
Miotkowski, I.
Powiązania:
https://bibliotekanauki.pl/articles/1929694.pdf
Data publikacji:
1993-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
75.50.Pp
72.40.+w
Opis:
We report milikelvin studies of light induced metastable changes of the conductivity of the In doped Cd$\text{}_{0.95}$Mn$\text{}_{0.05}$Te$\text{}_{0.97}$Se$\text{}_{0.03}$ crystals in the vicinity of the metal-insulator transition.
Źródło:
Acta Physica Polonica A; 1993, 84, 4; 657-660
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
High-Temperature Scanning Tunnelling Spectroscopy of Transition Metal Oxides
Autorzy:
Klusek, Z.
Datta, P. K.
Kowalczyk, P.
Pierzgalski, S.
Busiakiewicz, A.
Olejniczak, W.
Basu, A.
Brinkman, A.
Powiązania:
https://bibliotekanauki.pl/articles/2036892.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
73.20.At
72.80.Ga
Opis:
In situ high-temperature scanning tunnelling spectroscopy measure-ments recorded on the heavily reduced TiO$\text{}_{2}$(110) surface which contains Ti$\text{}_{2}$O$\text{}_{3}$ regions showed disappearance of the energy gap accompanied by substantial decrease in amplitude of the band edge states with increasing temperature. It indicates smooth insulator-metal transition caused by bands overlap in Ti$\text{}_{2}$O$\text{}_{3}$, which takes place at elevated temperatures. In situ high-temperature scanning tunnelling microscopy and spectroscopy were used to study the influence of temperature on the electronic properties of Ni$\text{}_{x}$Mn$\text{}_{3-x}$O$\text{}_{3-δ}$ (0.4< x<1) thin films deposited by rf magnetron sputtering at three different oxygen/argon (2.5%, 10%, 15%) containing ambient. The morphology and distribution of the local density of states of the observed films did not show any difference for the films deposited at different conditions. The distribution of the local density of states was temperature dependent. The changes in the shape of the local density of states observed at 473 K were reversible with temperature implying that no permanent change of the electronic structure occurred.
Źródło:
Acta Physica Polonica A; 2003, 104, 3-4; 245-258
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Particle-Hole Symmetry of Charge Excitation Spectra in the Paramagnetic Phase of the Hubbard Model
Autorzy:
Dao, Vu
Frésard, Raymond
Powiązania:
https://bibliotekanauki.pl/articles/1029745.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
72.15.Nj
71.30.+h
Opis:
The Kotliar and Ruckenstein slave-boson representation of the Hubbard model allows to obtain an approximation of the charge dynamical response function resulting from the Gaussian fluctuations around the paramagnetic saddle-point in analytical form. Numerical evaluation in the thermodynamical limit yields charge excitation spectra consisting of a continuum, a gapless collective mode with anisotropic zero-sound velocity, and a correlation induced high-frequency mode at ω ≈ U. In this work we show that this analytical expression obeys the particle-hole symmetry of the model on any bipartite lattice with one atom in the unit cell. Other formal aspects of the approach are also addressed.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 336-342
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Partial Localization of Correlated Electrons in an Orbitally Degenerate Narrow Band: Spin Dependent Masses, Saturated Ferromagnetism, and the Effective s-d Model
Autorzy:
Jędrak, J.
Spałek, J.
Zwicknagl, G.
Powiązania:
https://bibliotekanauki.pl/articles/2047325.pdf
Data publikacji:
2007-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
71.30.+h
75.10.Lp
Opis:
We determined the localization threshold in a partially filled and doubly degenerate model of correlated electrons. Particular emphasis is put on a non-integer band filling n≥1, when the system decomposes into the localized and the itinerant subsystems; this situation is described by an effective s-d model. A simultaneous transition to the ferromagnetic state is discussed as driven by the Hund rule coupling combined with the effective field coming from the correlations. The dependence of the quasiparticle mass on the spin direction appears naturally in the spin-polarized phase and is attributed to the electron correlation effects, as is also a metamagnetic transition in an applied field. Although the main results were obtained within the saddle point slave-boson approach, their qualitative features are discussed in general terms, i.e. as a transition from quantum-mechanical indistinguishability of particles forming the Fermi fluid to a two-component situation.
Źródło:
Acta Physica Polonica A; 2007, 111, 4; 619-633
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative Study of the Electronic Structures of $Fe_3O_4$ and $Fe_2SiO_4$
Autorzy:
Piekarz, P.
Oleś, A.
Parlinski, K.
Powiązania:
https://bibliotekanauki.pl/articles/1536886.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
71.30.+h
71.38.-k
Opis:
The electronic properties of two spinels $Fe_3O_4$ and $Fe_2SiO_4$ are studied by the density functional theory. The local Coulomb repulsion U and the Hund exchange J between the 3d electrons on iron are included. For U = 0, both spinels are half-metals, with the minority $t_{2g}$ states at the Fermi level. Magnetite remains a metal in a cubic phase even at large values of U. The metal-insulator transition is induced by the $X_3$ phonon, which lowers the total energy and stabilizes the charge-orbital ordering. $Fe_2SiO_4$ transforms to a Mott insulating state for U > 2 eV with a gap $Δ_g$ ~ U. The antiferromagnetic interactions induce the tetragonal distortion, which releases the geometrical frustration and stabilizes the long-range order. The differences of electronic structures in the high-symmetry cubic phases and the distorted low-symmetry phases of both spinels are discussed.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 307-312
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-Fermi Liquid Behavior of Correlated Fermions in Applied Field
Autorzy:
Korbel, P.
Spałek, J.
Wójcik, W.
Powiązania:
https://bibliotekanauki.pl/articles/1964622.pdf
Data publikacji:
1997-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
71.30.+h
71.10.Fd
Opis:
We have determined an instability of the Fermi-liquid state of almost localized fermions in an applied magnetic field. It is proposed that a transition to a strongly correlated fermions (statistical-spin-liquid) state takes place at that point. The resultant magnetization curve and the field dependence of the specific heat are calculated and compared with those for CeRu$\text{}_{2}$Si$\text{}_{2}$.
Źródło:
Acta Physica Polonica A; 1997, 92, 2; 323-326
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reentrant Metal-Insulator Transition in $Ca_{1-x}Eu_{x}B_{6}$
Autorzy:
Glushkov, V.
Anisimov, M.
Baybakov, R.
Demishev, S.
Filippov, V.
Flachbart, K.
Kuznetsov, A.
Shitsevalova, N.
Sluchanko, N.
Powiązania:
https://bibliotekanauki.pl/articles/1369362.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.15.Gd
75.47.Gk
Opis:
Resistivity, Hall and Seebeck effects have been studied on single crystals of $Ca_{1-x}Eu_{x}B_{6}$ (0 ≤ x ≤ 1) at temperatures 2-300 K and in magnetic fields up to 8 T. An insulating ground state is found to be limited by narrow range of Eu doping 0.6 ≤ x ≤ 0.8. This region is characterized by an enhanced colossal magnetoresistance (CMR), which reaches values of ρ(0)/ρ(7T) > $10^{6}$ for x = 0.63 at T < 10 K. Decreasing of Eu content in $Ca_{1-x}Eu_{x}B_{6}$ below x* ≈ 0.6 restores the metallic ground state with moderate resistivity (ρ ~ 1 ÷ 5 mΩ·cm) and CMR amplitude (ρ(0)/ρ(7T) < 7). The second metal-insulator transition (MIT) in $Ca_{1-x}Eu_{x}B_{6}$ is observed beyond the whole conductivity region found earlier in the narrow range of Eu doping (0.7 ≤ x ≤ 0.8). The correlation between the enhanced CMR amplitude, the onset of positive diffusive thermopower and the elevation of anomalous Hall effect, determined for Eu content 0.6 ≤ x ≤ 0.85, favors the idea that a smooth change of band structure is the main factor governing the reentrant MIT in $Ca_{1-x}Eu_{x}B_{6}$.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 294-295
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron Correlation Phenomena in Selected Transition Metal Oxides
Autorzy:
Honig, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/1860849.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
71.30.+h
75.10.Lp
Opis:
The theory of electron correlation phenomena is reviewed and used to interpret the transport, thermal, or magnetic properties of V_{2}O_{3}, LaNiO_{3} and Fe_{3}O_{4} systems, each of which to a greater or lesser degree displays correlation effects. A rationale is provided for interpreting the various types of phase transitions encountered in the vanadium sesquioxide and magnetite host systems and to show why these are altered by small compositional variations.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 53-77
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stabilization of Kondo Semiconductor State by Sb Doping of $CeNi_{1-δ}Sn_{1+δ}$ and the General Criterion of Its Appearance
Autorzy:
Spałek, J.
Ślebarski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1812262.pdf
Data publikacji:
2008-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
72.15.Qm
71.30.+h
Opis:
Semimetallic off-stoichiometric $CeNi_{1-δ}Sn_{1+δ-x}Sb_x$ system with δ≈0.06 is shown to transform into a Kondo semiconductor upon the substitution of few percent of Sb for Sn. The full-gap formation is associated with f-electron localization induced by the combined effect of the collective Kondo-singlet formation and the atomic disorder. Namely, the extra valence electrons introduced with the Sb doping (one per Sb atom) contribute additionally to the formation of the collective Kondo spin-singlet state at low temperatures, as seen by a substantial reduction of the magnetic susceptibility. The precise general definition of the Kondo semiconductor is provided and the difference with either the simple band or the Mott-Hubbard insulators is stressed.
Źródło:
Acta Physica Polonica A; 2008, 114, 1; 7-14
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Critical Exponents for Metal-Insulator Transition in Two-Dimensional Systems
Autorzy:
Wojtkiewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/1808033.pdf
Data publikacji:
2009-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.10.Fd
02.40.Xx
Opis:
Three years ago, a new universality class, associated with the metal-insulator transition in quasi-two-dimensional compounds, was discovered. Imada has given explanation of the observed critical behaviour. Considerations in this work are based on the assumption that the one-particle dispersion is quartic one instead of the standard quadratic behaviour. In this paper, it is shown that other possible natural non-standard dispersions lead to other possible critical behaviour and critical exponents.
Źródło:
Acta Physica Polonica A; 2009, 115, 5; 931-934
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Link between Magnetic and Dielectric Properties in Magnetite
Autorzy:
Švindrych, Z.
Youssef, A.
Janů, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1534794.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
75.60.-d
75.85.+t
Opis:
We have measured temperature dependence of magnetic and dielectric properties in high quality stoichiometric single-crystals of magnetite $(Fe_3O_4)$. At low temperatures, below the Verwey transition, both ac susceptibility and ac permittivity reveal similar relaxation processes. We discuss these effects in connection with domain structure and variable range hopping mechanism of electrical conductivity.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 940-941
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlated Electron Systems of Different Dimensionalities
Autorzy:
Kurzyk, J.
Wójcik, W.
Spałek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1812297.pdf
Data publikacji:
2008-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
71.30.+h
71.10.Fd
Opis:
The optimized single-particle wave functions contained in the parameters of the Hubbard model (hopping integral t and intraatomic interaction U) are determined explicitly in the correlated state for electronic systems of various symmetries and dimensions: Hubbard chain, square and triangular lattices, and the three cubic lattices: SC, BCC, and FCC. In effect, the electronic properties of these structures as a function of the interatomic distance R are obtained. In most cases, the model parameters do not scale linearly with the lattice constant. Also, the atomic part of the total ground state energy changes with the U/t ratio and therefore should be (and is) included in the analysis. The solutions of dimensions D>1 are analyzed by utilizing the approximate Gutzwiller treatment.
Źródło:
Acta Physica Polonica A; 2008, 114, 1; 175-178
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Radiative Recombination Spectra of Heavily p-Type δ-Doped GaAs/AlAs MQWs
Autorzy:
Kundrotas, J.
Čerškus, A.
Valušis, G.
Lachab, M.
Khanna, S.
Harrison, P.
Linfield, E.
Powiązania:
https://bibliotekanauki.pl/articles/1813382.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.-m
78.67.De
71.30.+h
Opis:
We present a study of the photoluminescence properties of heavily Be δ-doped GaAs/AlAs multiple quantum wells measured at room and liquid nitrogen temperatures. Possible mechanisms for photocarriers recombination are discussed, with a particular focus on the peculiarities of the excitonic and free carriers-acceptors photoluminescence emissions occurring below and above the Mott metal-insulator transition. Moreover, based on a simple theoretical model, it is found that the critical impurities concentration to observe the Mott transition in the multiple quantum wells samples exhibiting 15 nm wells width and 5 nm thick barrier layers is ≈3×$10^{12} cm^{-2}$.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 963-966
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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