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Wyświetlanie 1-15 z 300
Tytuł:
Hexammine Nickel Complex: Cooperative Rotation of Six NH$\text{}_{3}$ Groups
Autorzy:
Sczaniecki, P. B.
Powiązania:
https://bibliotekanauki.pl/articles/1931836.pdf
Data publikacji:
1994-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.-v
Opis:
Electrostatic interactions between NH3 groups undergoing a correlated rotation are calculated with reference to the nickel hexammine complexes [Ni(NH$\text{}_{3}$)$\text{}_{6}$]$\text{}^{2+}$ The results demonstrate the angular dependence of the cis and trans arrangements of the model ammonia triangles. The previously defined four maxima and four minima are identified.
Źródło:
Acta Physica Polonica A; 1994, 86, 6; 1021-1026
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transport and Magnetoresistance in Low Carrier Density Ferromagnets
Autorzy:
Littlewood, P. B.
Powiązania:
https://bibliotekanauki.pl/articles/2011203.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.70.Pa
Opis:
In metallic magnets, scattering from magnetic fluctuations above and near T$\text{}_{C}$ may provide a substantial contribution to the electrical resistance ρ(T). However, this effect is usually small because the dominant fluctuations are near q ≈ 0, which does not produce substantial backscattering across the Fermi surface unless 2k$\text{}_{F}$ is itself small; such a situation can be realised in metallically-doped ferromagnetic semiconductors. A simple adaptation of the theory of deGennes and Friedel shows the low field magnetoresistance scales with the ratio of field induced magnetisation m(H) to the saturation magnetisation m$\text{}_{sat}$: Δρ/ρ ≈ C(m/m$\text{}_{sat}$)$\text{}^{2}$, where C ≈ x$\text{}^{-2}\text{}^{/}\text{}^{3}$ , with x the number of charge carriers per magnetic unit cell. Comparison to data on very different ferromagnetic metals and doped semiconductors is in broad quantitative agreement with this trend, with the prime exception of the perovskite manganese oxides, already understood to involve the extra physics of dynamic lattice distortions. At very low doping, the physics should involve ferromagnetic polarons, and polaron formation and transport are discussed.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 7-13
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wavelet Analysis in EPR Spectroscopy
Autorzy:
Drzewiecki, A.
Sczaniecki, P. B.
Powiązania:
https://bibliotekanauki.pl/articles/2043391.pdf
Data publikacji:
2005-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
07.05.Kf
76.30.Rn
82.50.Kx
Opis:
Possibility of application of wavelet analysis in EPR spectroscopy is investigated. Basic mathematics of the method is summarized, with emphasis on the relation between EPR experiment and physical interpretation of wavelet transform. The fact that first derivative of the Lorentzian function can be used as a base wavelet is employed and the specific rules of the interpretation of the final wavelet synthesis are identified. Analysis of a sample EPR spectrum of X-ray irradiated guanidinium aluminium sulphate hexahydrate crystal is given as an example. Set of parameters resulting from the wavelet analysis is subsequently used to reconstruct/synthesize the original EPR spectrum. The method involves an opportunity of eliminating unwanted components of the multicomponent spectra. Generally, the method may supplement other means of data analysis, in particular, in magnetic resonance.
Źródło:
Acta Physica Polonica A; 2005, 108, 1; 73-79
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature Dependence ofĝ Tensor Anisotropy in (tm-p-PD):Chloranil, Charge Transfer Complex Powders
Autorzy:
Grampp, G.
Sczaniecki, P. B.
Żurek, S.
Bednarski, W.
Powiązania:
https://bibliotekanauki.pl/articles/2043604.pdf
Data publikacji:
2005-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.Rn
Opis:
The powders of 2,3,5,6-tetramethyl-p-phenylenediamine:chloranil charge transfer complex were studied by EPR. Numerical pack EPR-NMR was used to simulate and fit the X-band experimental data in the temperature range of 119-298 K. Very good agreement between the experiment and simulations permits to obtain the main values ofĝ matrix and plot their temperature dependence. At 150 K the main g values are g$\text{}_{xx}$=g$\text{}_{yy}$=2.0041 and g$\text{}_{zz}$=2.0015. g splitting factor varies significantly with temperature and shows an anomaly near 200 K. The signal narrows with the temperature increase, which agrees with the earlier observation. Individual component linewidth, used in the simulation is anisotropic and amounts to 0.1-0.8 mT; which is reasonable when compared with those measured earlier for the single crystals of p-phenylenediamine:chloranil, where the narrowest lines are quoted to be 18μT.
Źródło:
Acta Physica Polonica A; 2005, 108, 2; 317-321
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase and Structural Study of Self-Doped La$\text{}_{1-x-y}$Ca$\text{}_{x}$Ø$\text{}_{y}$MnO$\text{}_{3+δ}$
Autorzy:
Figueiras, F.
Araújo, J. P.
Amaral, V. S.
Tavares, P. B.
Lopes, A. B.
Vieira, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/2037125.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.75.+g
81.40.Rs
75.50.-y
72.20.My
Opis:
To understand the combined effect of divalent ion and A-site vacancy (Ø) self-doping, beyond the binary La$\text{}_{1-x}$MnO$\text{}_{3}$ system, polycrystalline La$\text{}_{1-x-y}$Ca$\text{}_{x}$Ø$\text{}_{y}$MnO$\text{}_{3+δ}$ samples were studied. Samples with Ca substitution and excess Mn in the range x<0.33 and y<0.45, respectively, were prepared by standard solid-state reactions. Structural and phase analysis of the samples were done by X-ray diffraction and transmission electron microscopy. The manganite structure in this composition range includes rhombic and orthorhombic phases. Most samples contain the hausmanite phase (Mn$\text{}_{3}$O$\text{}_{4}$) coexisting with the manganite phase. A small amount of perovskite related AMn$\text{}_{7}$O$\text{}_{12}$ (A=La,Ca) structure near the hausmanite-manganite boundary is also found in samples treated in oxygen atmosphere. The calculated vacancy content accommodated in the manganite phase can be higher than 1/8, the reported limit for La$\text{}_{1-x}$MnO$\text{}_{3}$, which is confirmed in our x=0 sample. For the compositions studied, a ferromagnetic metallic behavior below T$\text{}_{C}$ is found, confirming the stability of the Mn sublattice, and near the optimum stoichiometric ((x=0. 33, y=0) system, a net A-site vacancy content (up to y=0.2) does not degrade the magnetic and electric properties.
Źródło:
Acta Physica Polonica A; 2004, 105, 1-2; 173-182
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Charge-Ordering and Magnetoelastic Coupling Effects on the Magnetocaloric Properties of Manganites
Autorzy:
Reis, M. S.
Gomes, A. M.
Araújo, J. P.
Tavares, P. B.
Amaral, J. S.
Oliveira, I. S.
Amaral, V. S.
Powiązania:
https://bibliotekanauki.pl/articles/2037124.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Sg
75.30.Kz
75.80.+q
Opis:
A study of the magnetocaloric properties of La$\text{}_{1-x-y}$Y$\text{}_{y}$Ca$\text{}_{x}$MnO$\text{}_{3}$, La$\text{}_{1-x}$Cd$\text{}_{x}$MnO$\text{}_{3}$, and Pr$\text{}_{1-x}$Ca$\text{}_{x}$MnO$\text{}_{3}$ manganites with ferromagnetic and charge-ordered states is presented. The ferromagnetic lanthanum manganites show a negative entropy change peakΔ S under the application of a magnetic field at the Curie temperature. However, the magnetoelastic coupling effects lead to a first-order paramagnetic-ferromagn etic transition and an increasedΔ S compared to simple ferromagnets. This effect is analyzed in the framework of the Landau theory of phase transitions which shows a comparable influence of the magnetoelastic couplings and the ordinary magnetic ordering effect. The Pr$\text{}_{1-x}$Ca$\text{}_{x}$MnO $\text{}_{3}$ system shows a rich electric and magnetic phase diagram, with a ferromagnetic insulator phase for 0.15
Źródło:
Acta Physica Polonica A; 2004, 105, 1-2; 163-171
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stochastic Carrier Dynamics in Semiconductor Superlattices
Autorzy:
Fromhold, T. M.
Bujkiewicz, S.
Patanè, A.
Stapleton, S. P.
Sherwood, D.
Fowler, D.
Cooper, J.
Eaves, L.
Belyaev, A. E.
Krokhin, A. A.
Neumann, A.
Wilkinson, P. B.
Sankeshwar, N. S.
Henini, M.
Sheard, F. W.
Powiązania:
https://bibliotekanauki.pl/articles/2044604.pdf
Data publikacji:
2006-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.At
73.21.Cd
Opis:
We explore a new regime of hot carrier dynamics, in which electrons in a superlattice miniband exhibit a unique type of stochastic motion when a magnetic field is tilted at an angle θ to the superlattice axis. Remarkably, the dynamics of a miniband electron in a tilted magnetic field reduce to a one-dimensional simple harmonic oscillator, of angular frequency ω$\text{}_{C}$ cos θ, where ω$\text{}_{C}$ is the cyclotron frequency, driven by a time-dependent plane wave whose angular frequency equals the Bloch frequency ω$\text{}_{B}$. At bias voltages for which ω$\text{}_{B}$=nω$\text{}_{C}$ cos θ, where n is an integer, the electron orbits change from localised Bloch-like trajectories to unbounded stochastic orbits, which diffuse rapidly through intricate web patterns in phase space. To quantify how these webs affect electron transport, we make drift-diffusion calculations of the current-voltage curves including the effects of space-charge build up. When the magnetic field is tilted, our simulations reveal a large resonant peak, which originates from stochastic delocalisation of the electron orbits. We show that the corresponding quantised eigenstates change discontinuously from a highly localised character when the system is off resonance to a fully delocalised form when the resonance condition is satisfied.
Źródło:
Acta Physica Polonica A; 2006, 109, 1; 43-52
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of DI-Hydrogen-Monovacancy Defect in Silicon
Autorzy:
Stallinga, P.
Nielsen, B. B.
Powiązania:
https://bibliotekanauki.pl/articles/1968423.pdf
Data publikacji:
1997-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.Lh
76.70.Hb
76.30.-v
Opis:
A careful analysis of the alleged electron paramagnetic resonance spectrum of VH$\text{}_{2}$ in silicon is made. The parameters of this spectrum coincide with those of the well-known excited state (S=1) spectrum of the oxygen vacancy defect. The conclusion is reached that they are one and the same.
Źródło:
Acta Physica Polonica A; 1997, 92, 5; 989-992
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parallel Optical Profilometry Assisted Conception of an Opto-Electronic Illuminator Using a VCSEL and Diffractive Optics
Autorzy:
Montgomery, P.
Serio, B.
Twardowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/1197891.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
85.85.+j
42.55.Px
42.40.Eq
42.87.Bg
68.35.bg
Opis:
Micro-opto electromechanical systems are of growing importance in the development of new miniaturised projection, imaging and detection technologies. Because of the increasing complexity of construction involving layers of microelectronics, optoelectronics and micro-optics, different types of defects can appear that need to be understood and controlled in order for the miniaturised system to operate correctly within the given specifications. We have recently developed a miniaturised structured light (micro-opto electromechanical systems) projector consisting of a multilayer sandwich made of a first layer of 3 bars of 12 VCSEL laser sources, a second layer of Fresnel collimating lenses (diffractive optical elements) and a third layer of Fourier diffractive optical elements to produce the structured light pattern. The main defects that had to be controlled were alignment errors, the first ones being between the emitting surface and the collimating lenses and the second one concerning the lateral alignment of the photomasks used to produce the 4 levels of the Fourier elements. We demonstrate how 3D geometrical shape characterization of the emitting structures and diffractive optical elements surface structures using coherence scanning interferometry played a major role in the conception and fabrication of a prototype micro-optoelectromechanical projection system to understand the source of the alignment errors and to minimise them.
Źródło:
Acta Physica Polonica A; 2014, 125, 4; 957-961
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Oxygen Adsorption on Electronic Structure of Iron Phthalocyanine
Autorzy:
Białek, B.
Brągiel, P.
Powiązania:
https://bibliotekanauki.pl/articles/1945276.pdf
Data publikacji:
1996-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.+x
Opis:
Self-consistent field ab initio calculations were performed in order to determine the electronic structure of iron phthalocyanine (FePc) and its changes under interaction with the O$\text{}_{2}$ molecule. The experimental evidence related to O$\text{}_{2}$ adsorption on phthalocyanine plane was confirmed. The possible charge transfer between phthalocyanine and O$\text{}_{2}$ molecule is briefly discussed. Considerable displacement of energy levels in the case of oxygen adsorption on FePc plane has been noticed.
Źródło:
Acta Physica Polonica A; 1996, 89, 3; 443-449
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Simulations of 0.25 Monolayer Iodine Adsorption on Cu(100)
Autorzy:
Mikołajczyk, P.
Stankiewicz, B.
Powiązania:
https://bibliotekanauki.pl/articles/1811509.pdf
Data publikacji:
2008-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.43.Bc
68.43.Fg
68.37.Ef
Opis:
Simulations of adsorption 0.25 monolayer of iodine on Cu(100) were performed using a local-orbital minimal basis technique based on density functional theory and compared with plane-wave basis results. It was found that iodine adsorption changes the spacings between surface layers of copper substrate and can cause the reconstruction of this surface to rhombus-like arrangement with a stable threefold hollow adsorption site. The calculated structure of I/Cu(100) is presented together with the simulated scanning tunneling microscopy images of this surface. The obtained results are discussed in comparison with experimental results.
Źródło:
Acta Physica Polonica A; 2008, 114, S; S-71-S-76
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vibronic Magnetoelectric Effects in the Bi-Based Multiferroics
Autorzy:
Konsin, P.
Sorkin, B.
Powiązania:
https://bibliotekanauki.pl/articles/1384870.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.kd
77.84.-s
77.80.Bh
77.80.-e
Opis:
The detailed magneto-electron-lattice (vibronic) theory of ferroelectricity in the Bi-based multiferroics (BiFeO₃ etc.) is developed further. The vibronic admixture of the empty oxygen 2p states to the Bi 6s lone electron pair state leads to ferroelectricity. These interactions are the driving and restoring forces of the structural phase transformations of the Bi-based multiferroics. The free energy of the BiFeO₃-type multiferroics with the ferroelectric and the G-type antiferromagnetic phase transitions are derived. The Zeeman splitting and spin-transversal optical phonon couplings are also important.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 243-244
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The J₁-J₂ Model on the Anisotropic Triangular and the Square Lattice: Similarities and Differences
Autorzy:
Schmidt, B.
Thalmeier, P.
Powiązania:
https://bibliotekanauki.pl/articles/1385520.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Jm
75.30.Cr
75.30.Ds
Opis:
The Heisenberg model on a triangular lattice is a prime example for a geometrically frustrated spin system. However most experimentally accessible compounds have spatially anisotropic exchange interactions. As a function of this anisotropy, ground states with different magnetic properties can be realized. On the other hand, the J₁-J₂ model on the square lattice is a well-known example for frustration induced by competing exchange. The classical phase diagrams of the two models are related in a broad range of the control parameter ϕ=$tan^{-1}$(J₂/J₁). In both cases three different types of ground states are realized, each model having a ferromagnetic and an antiferromagnetic region in the phase diagram, and a third phase with columnar magnetic order for the square lattice and an in general incommensurate spiral structure for the triangular lattice. Quantum effects lift degeneracies in the non-FM phases and lead to additional nonmagnetic regions in the phase diagrams. The contribution of zero point fluctuations to ground state energy, wave vector, and ordered moment is discussed.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 324-326
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nanodevice for High Precision Readout of Electron Spin
Autorzy:
Szumniak, P.
Bednarek, S.
Szafran, B.
Grynkiewicz, P.
Powiązania:
https://bibliotekanauki.pl/articles/2048078.pdf
Data publikacji:
2011-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
73.63.Nm
03.67.Lx
05.45.Yv
Opis:
In this paper we propose and simulate operation of a nanodevice, which enables the electron spin accumulation and very precise read-out of its final value. We exploit the dependence of the electron trajectory on its spin state due to the spin-orbit coupling in order to distinguish between different spin orientations.
Źródło:
Acta Physica Polonica A; 2011, 119, 5; 651-653
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Intrinsic Luminescence of the Undoped Glasses of (CaO-Ga$\text{}_{2}$O$\text{}_{3}$-GeO$\text{}_{2}$) System
Autorzy:
Padlyak, B. V.
Bordun, O. M.
Buchynskii, P. P.
Powiązania:
https://bibliotekanauki.pl/articles/2010938.pdf
Data publikacji:
1999-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.70.Ce
78.60.-b
76.30.Mi
Opis:
For the first time the intrinsic luminescence in the undoped (CaO-Ga$\text{}_{2}$O$\text{}_{3}$-GeO$\text{}_{2}$) glasses with different composition has been found and investigated in the 80÷300 K temperature range. The new glasses of high chemical purity and optical quality with stoichiometric composition similar to that in calcium-gallium- germanium garnet (Ca$\text{}_{3}$Ga$\text{}_{2}$Ge$\text{}_{3}$O$\text{}_{12}$), trigonal Ca-gallogermanate (Ca$\text{}_{3}$Ga$\text{}_{2}$Ge$\text{}_{4}$O$\text{}_{14}$), and Ca$\text{}_{3}$Ga$\text{}_{2}$O$\text{}_{6}$ crystals were obtained by the high-temperature synthesis method. The luminescence and photoexcitation spectra analysis, supported by EPR spectroscopy data, yields the following results: (i) the UV-excited non-elementary broad emission band with maxima at roughly 500 nm and 420 nm in the (CaO-Ga$\text{}_{2}$O$\text{}_{3}$-GeO$\text{}_{2}$) glasses is due to recombination of ensemble of the transient hole O$\text{}^{-}$ centres; (ii) the emission bands with maxima at nearly 380 and 710 nm, which were distinctly revealed in glasses with the Ca$\text{}_{3}$Ga$\text{}_{2}$Ge$\text{}_{4}$O$\text{}_{14}$ and Ca$\text{}_{3}$Ga$\text{}_{2}$O$\text{}_{6}$ compositions, are assigned to the luminescence of UV-induced electron centres of two different types. Possible models of the luminescence centres in (CaO-Ga$\text{}_{2}$O$\text{}_{3}$-GeO$\text{}_{2}$) glass network are discussed.
Źródło:
Acta Physica Polonica A; 1999, 95, 6; 921-929
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 300

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