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Wyświetlanie 1-15 z 42
Tytuł:
Parametrization of the Bilinear Orbit—Lattice Interaction
Autorzy:
Pastusiak, W.
Powiązania:
https://bibliotekanauki.pl/articles/1888013.pdf
Data publikacji:
1991-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
Opis:
A group theoretical parametrization scheme of the bilinear orbit-lattice interaction is presented. Using this scheme a general analytical form of this interaction in the point-charge electrostatic model has been obtained. Based on this general analytical form the second-order parameters of the bilinear orbit-lattice interaction have been calculated for a tetrahedral complex. For cubic complexes a microscopic interpretation of the G-tensor components in the long-wavelength approximation of acoustic waves is given for the first time. The presented scheme of parametrization as well as the method of calculations of the interaction parameters may be extended to other models of the crystal field.
Źródło:
Acta Physica Polonica A; 1991, 80, 1; 107-116
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin-Orbit Coupling for f-Electrons in a Crystalline Field
Autorzy:
Lulek, T.
Powiązania:
https://bibliotekanauki.pl/articles/1929779.pdf
Data publikacji:
1993-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
Opis:
The notion of a spin-orbit interaction arises from consideration of dynamics of multielectron atoms, i.e. systems of N electrons in a spherical potential. This notion is essentially a single-particle one. We sketch its origin as a second-order correction when Dirac four-component wave equations for an electron in external electromagnetic fields are simplified to the two-component Pauli spinors. The constraints in spinorial degrees of freedom consist, roughly speaking, in neglecting the small component of the electron four-function. The spin-orbit interaction term serves to compensate effects of the small component. The crystalline field induces some deviations from spherical symmetry of an isolated atom, which yields some modifications of the spherical form of the spin-orbit interaction operator. These modifications can be described in terms of a number of tensor operators adapted to appropriate chains of subgroups of the spherical symmetry group. We present a classification of independent tensor operators and discuss the relevant parameters for f-ions.
Źródło:
Acta Physica Polonica A; 1993, 84, 5; 867-873
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rationalization of Spectra of Rare Earths in Condensed Matter
Autorzy:
Reisfeld, R.
Jørgensen, C. K.
Powiązania:
https://bibliotekanauki.pl/articles/1929810.pdf
Data publikacji:
1993-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
Opis:
The parametrized models are compared with counter-intuitive consequences of the non-relativistic Schrödinger treatment. For both 4f$\text{}^{ q}$, 5f$\text{}^{ q}$ and d$\text{}^{9}$ systems in condensed matter, the energy levels must be strongly influenced by correlation effects. The parametrization of intensities is conceptually very different for f$\text{}^{ q}$ and d$\text{}^{9}$ compounds. The bandwidths of absorption and luminescence are discussed and related to the Born-Oppenheimer factorization.
Źródło:
Acta Physica Polonica A; 1993, 84, 5; 1011-1019
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low Temperature Magnetic Ordering in NdAgAl₃
Autorzy:
Nallamuthu, S.
Džubinská, A.
Reiffers, M.
Nagalakshmi, R.
Powiązania:
https://bibliotekanauki.pl/articles/1032835.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
65.40.Ba
Opis:
We present the detailed study of magnetic, thermodynamic, and transport properties of polycrystalline NdAgAl₃. The compound crystallizes in BaNiSn₃-type tetragonal structure with the space group I4mm. Magnetic, heat capacity and transport measurements indicate the possible antiferromagnetic nature of the ordering below 2 K. The compound shows the Schottky anomaly in heat capacity data. Magnetoresistance is negative at low temperature.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1015-1017
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetism and Crystal Field in PrCuAl₃ and NdCuAl₃
Autorzy:
Novák, P.
Diviš, M.
Powiązania:
https://bibliotekanauki.pl/articles/1032630.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
71.20.Lp
71.70.Ch
Opis:
During the last five years we developed method to calculate crystal field and magnetism of rare-earth ions in solids. The method is fully ab initio with the exception of a single parameter which adjust the position of f states relative to other valence states and it was successfully applied in insulating systems. In this contribution the method is used to explain multiplet splitting and magnetism in PrCuAl₃ and NdCuAl₃ intermetallics. For the Nd compound the agreement between theory and experiment is good, while for the PrCuAl₃ the agreement is less satisfactory which can be due to the more delocalized 4f electrons of Pr³⁺ comparing to Nd³⁺ ion.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 964-966
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Structure of $PrCo_2Ge_2$
Autorzy:
Diviš, M.
Vejpravová, J.
Rusz, J.
Prokleška, J.
Sechovský, V.
Powiązania:
https://bibliotekanauki.pl/articles/1813659.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
71.70.Ch
Opis:
The intermetallic compound $PrCo_2Ge_2$ exhibits very interesting physical properties: antiferromagnetism below $T_N$ = 28 K, an order to order transition at $T_R$ = 8 K, a rich magnetic phase diagram, and huge magnetocrystalline anisotropy as observed by recent experiments on a single crystal in a magnetic field up to 14 T. We performed first principles calculations based on the density functional theory. The localized $4f^2$ configuration of $Pr^{3+}$ was treated using the open core approximation. The electronic densities of states were obtained and the position of the Fermi level was found. The hybridization between the Co-3d, Pr-5d and Ge-4p states is discussed. The calculated magnetic moment of Co is found to be quite small $(m_{Co} < 0.1 μ_B)$. The first principles calculations of the crystal field interaction were performed as well: the obtained crystal field parameters were used as the starting parameters for further refinement in comparison with experimental data of the magnetic susceptibility and specific heat. The crystal field splitting of the 4f states was determined.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 295-298
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
d and f Electrons in a qp-Quantized Cubical Field
Autorzy:
Kibler, M.
Sztucki, J.
Powiązania:
https://bibliotekanauki.pl/articles/1929778.pdf
Data publikacji:
1993-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
03.65.-w
02.20.-a
Opis:
A procedure for qp-quantizing a crystal-field potential V with an arbitrary symmetry G is developed. Such a procedure is applied to the case where V involves cubic components (G = 0) of the degrees 4 and 6. This case corresponds to d and f electrons in a qp-quantized cubical potential. It is shown that the qp-quantization of the considered cubical potential is equivalent to a symmetry breaking of type O → D$\text{}_{4}$. A general conjecture about this symmetry breaking phenomenon is given.
Źródło:
Acta Physica Polonica A; 1993, 84, 5; 857-866
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Theoretical Analysis of Zero Field Splitting of $Mn^{2+}$ in Ammonium Oxalate Monohydrate
Autorzy:
Kripal, R.
Pandey, S.
Powiązania:
https://bibliotekanauki.pl/articles/1535738.pdf
Data publikacji:
2010-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
76.30.Fc
Opis:
The superposition model has been used to investigate the substitution of $Mn^{2+}$ in ammonium oxalate monohydrate. The zero field splitting parameters D and E calculated by the superposition model are compared with the experimental values $D_{exp}$ and $E_{exp}$, respectively, for $Mn^{2+}$ obtained by electron paramagnetic resonance. Both the zero field splitting parameters D and E calculated theoretically are in good agreement with the experimental values $D_{exp}$ and $E_{exp}$. The result indicates that the $Mn^{2+}$ ion substitutes for the $NH_4^{+}$ ion in ammonium oxalate monohydrate.
Źródło:
Acta Physica Polonica A; 2010, 118, 4; 629-632
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exchange Charge Model for $Fe^{3+}:LiAl_{5}O_{8}$
Autorzy:
Vaida, M.
Avram, C.
Powiązania:
https://bibliotekanauki.pl/articles/1791224.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
78.20.Bh
34.20.Cf
71.70.-d
Opis:
The aim of this paper is the theoretical investigation of $Fe^{3+}$ doped in the ordered phase of $LiAl_{5}O_8$. We used the shell model and pair potential approximation to optimize the geometric structure of $LiAl_{5}O_{8}$. This approach enables the modeling of the crystal field parameters of $LiAl_{5}O_8$ and then calculates the energy levels scheme of $Fe^{3+}$ ions doped in tetrahedral sites in the title crystal. Consistent crystal field analysis and the energy level splittings for $LiAl_{5}O_{8}$ doped with $Fe^{3+}$ ions was performed in the frame of the exchange charge model of crystal field. The comparison of the theoretically obtained results for energy levels with the experimental data, yields satisfactory agreement and confirms the validity of the exchange charge model.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 541-543
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Crystal Field Analysis of $Cr^{3+}$ Doped $SrAl_{2}O_{4}$ Spinel
Autorzy:
Stanciu, M.
Ciresan, M.
Avram, N.
Powiązania:
https://bibliotekanauki.pl/articles/1791232.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
68.47.Jn
71.70.Gm
Opis:
The present work is devoted to the crystal field analysis of trivalent chromium doped in $SrAl_{2}O_{4}$ spinel in the frame of the exchange charge model of crystal field. Using the shell model and pair approximation, we optimize the geometric structure of the crystal. The approach enables the modeling of the crystal field parameters and thus calculates the energy level scheme of $Cr^{3+}$ ions in spinel $SrAl_{2}O_{4}$. The obtained results are compared with experimental data and discussed.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 544-546
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Angular Distortion around $Cr^{3+}$ Ions Doped Diammonium Hexaaqua Magnesium Sulphate Single Crystal
Autorzy:
Ciresan, M.
Vaida, M.
Avram, N.
Powiązania:
https://bibliotekanauki.pl/articles/1815473.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Dg
76.30.-v
71.70.Ch
Opis:
The aim of the present study is to explain the local distortion around $Cr^{3+}$ ions doped in the title crystal using the latest experimental data regarding optical and EPR spectra. We calculated $g_ǁ$, $g_⊥$, and D spin-Hamiltonian parameter as function of angle between the $C_3$ axis and metal-ligand chemical bond in local distorted octahedral cluster $[CrO_6]^{9-}$ formed after doped crystal. The method is based on the single spin-orbit coupling parameter model, in the cluster approach using Macfarlane high order perturbation formulae. The results compared with experimental data give a reasonable agreement.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 835-839
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Specific Heat of Cr-Based Semimagnetic Semiconductors
Autorzy:
Twardowski, A.
Eggenkamp, P.
Mac, W.
Swagten, H. J. M.
Demianiuk, M.
Powiązania:
https://bibliotekanauki.pl/articles/1929660.pdf
Data publikacji:
1993-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
71.70.Ch
71.70.Ej
Opis:
Specific heat of ZnCrSe and ZnCrS was measured for 1.5 < T < 10 K and B < 3 T. The data were interpreted using "crystal field model" taking into account tetrahedral crystal field, tetragonal Jahn-Teller distortion and spin-orbit interaction.
Źródło:
Acta Physica Polonica A; 1993, 84, 3; 563-565
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Structure of Organometallic Complexes of f Elements. Are Molecular Orbital Calculations a Useful Tool for Spectroscopists?
Autorzy:
Jank, S.
Amberger, H.-D.
Powiązania:
https://bibliotekanauki.pl/articles/1945458.pdf
Data publikacji:
1996-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.65.Sq
71.70.Ch
Opis:
The crystal field parameters of base-free (Me$\text{}_{3}$SiC$\text{}_{5}$H$\text{}_{4}$)$\text{}_{3}$Pr, (C$\text{}_{5}$H$\text{}_{5}$)$\text{}_{3}$Pr·NCCH$\text{}_{3}$, (C$\text{}_{5}$H$\text{}_{5}$)$\text{}_{3}$La(NCCH$\text{}_{3}$)$\text{}_{2}$:Pr, [Pr(C$\text{}_{8}$H$\text{}_{8}$)]$\text{}^{+}$ and Nd[N(SiMe$\text{}_{3}$)$\text{}_{2}$]$\text{}_{3}$ as model compound for Nd[CH(SiMe$\text{}_{3}$)$\text{}_{2}$]$\text{}_{3}$ were inserted into the corresponding energy matrices of a model spin-free f$\text{}^{1}$ system. Diagonalizing these matrices the crystal field splitting patterns of the f orbitals were calculated. These experimentally based molecular orbital schemes are compared with the results of previous model calculations.
Źródło:
Acta Physica Polonica A; 1996, 90, 1; 21-32
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigations of the Optical and EPR Spectra for $Cr^{3+}$ Ions in Diammonium Hexaaqua Magnesium Sulphate Single Crystal
Autorzy:
Wei, Q.
Powiązania:
https://bibliotekanauki.pl/articles/1535818.pdf
Data publikacji:
2010-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.Fc
71.70.Ch
71.55.Ht
Opis:
The relations between spin-Hamiltonian parameters and local structure around $Cr^{3+}$ in diammonium hexaaqua magnesium sulphate single crystal were established. On the basis of this, the spin-Hamiltonian parameters, optical spectra and the local structure were investigated successfully. The calculated results are in good agreement with experimental data. This shows that the distortion model adopted in this paper is reasonable.
Źródło:
Acta Physica Polonica A; 2010, 118, 4; 670-672
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spectroscopic Study of Rare Earth Chromates: Relation to the Structure
Autorzy:
Antic-Fidancev, E.
Lemaitre-Blaise, M.
Parada, C.
Powiązania:
https://bibliotekanauki.pl/articles/1945460.pdf
Data publikacji:
1996-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.50.Dq
33.50.Hv
71.70.Ch
78.50.Ec
Opis:
The luminescence spectra of the trivalent europium ion embedded in various rare earth chromates were analyzed. The spectroscopic data in most of chromates are in agreement with the structural determination but for some others the discrepancy between two methods is underlined. Energy level schemes were deduced from the experimental emission spectra and the crystal field simulation has been performed. The maximum splitting of the $\text{}^{7}$F$\text{}_{1}$ manifold of the Eu$\text{}^{3+}$ ion as a function of N$\text{}_{v}$, the so-called crystal field strength parameter, is given. This allows us to classify the compounds according to their crystal field extent.
Źródło:
Acta Physica Polonica A; 1996, 90, 1; 33-44
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 42

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