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1
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Effect of the Order on the Structural and Magnetic Properties of Fe-X (X=Al, Si) Alloys with B2 Structure

100%
Deniszczyk J.
Acta Physica Polonica A
|
2000
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vol. 98
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issue 5
543-546
EN
Previous ab initio super-cell calculations of the magnetic properties of the ordered Fe_{1-x}Al_{x} alloy in the B2 structure are extended to include the disordered state of the alloy and completed with the calculations for ordered and disordered Fe_{1-x}Si_{x} alloys. The configurations of the Fe atoms in the anti-site (AS) positions of Fe-X super-cell with the antiferromagnetic order were found. The ground state of Fe_{1-x}Al_{x} with x≃ 0.3 shows the antiferromagnetic order of the Fe-AS magnetic moments. The concentration dependence of the equilibrium lattice parameter and magnetic moment of Fe_{1-x}X_{x} in the ordered and disordered state differ qualitatively.
2
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Influence of the Local Environment on the Magnetic Properties of the Ordered Fe_{1-x}Al_{x} Alloy

100%
Deniszczyk J.
Acta Physica Polonica A
|
2000
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vol. 97
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issue 3
583-586
EN
The electronic and magnetic properties of the ordered binary Fe_{1-x}Al_{x} alloy with the B2 crystal structure were calculated for Al concentrations x=0.1875-0.5 using the supercell structure. The calculations showed that for increasing Al contents the average magnetization of Fe_{1-x}Al_{x} falls down rapidly. Upon lowering the unit cell volume, almost all configurations of compositions with x ≥ 0.25 show the abrupt change of magnetic state from the high moment magnetic state to the low moment magnetic state with the moment reduction 0.6-0.8 μ_{B} per atom. The configurations were found for which the low moment magnetic state solutions with the antiferromagnetic alignment of magnetic moments of Fe atoms at antisite positions are stable.
3
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Band Structure and Magnetic Properties of DO_{3}-Type Fe_{3-x}V_{x}Al Alloys. Super-Cell Approach

64%
Deniszczyk J., Borgieł W.
Acta Physica Polonica A
|
2000
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vol. 98
|
issue 5
551-554
EN
The electronic structure of Fe_{3-x}V_{x}Al alloys was calculated using the super-cell methodology of alloy modeling. The concentration range of x=0.0÷1.0 was investigated. For a concentration of x=0.0625 the energy based analysis reveals that vanadium prefers to replace the Fe atom at sites with the octahedral coordination. It was found that the iron atoms coordinated by the eight nearest-neighbor Fe atoms preserve their high magnetic moment up to a concentration of x=0.9375 even though the average total magnetic moment goes to zero. The relatively high (≃ -1.0μB) negative magnetic moment of V remains constant up to x≃ 0.5. In the concentration range of x=0.75÷0.9375 the gap at ε_{F} of the minority density of states is observed while the majority density of states displays a sharp peak structure at the Fermi energy. This feature suggests the heavy-fermion behavior of the Fe_{2}VAl compound.
4
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Theoretical and Mössbauer Effect Study of Magnetic and Electronic Properties of Fe_{3}Al Compound

64%
Deniszczyk J., Frąckowiak J. E.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
455-458
EN
The electronic properties of Fe_{3}Al were determined experimentally, with the use of the Mossbauer spectroscopy, and theoretically. The band structure of the compounds was investigated applying the self-consistent tight-binding linear muffin tin orbital method. The calculated Fermi contact term of hyperfine fields and the isomer shifts are in good agreement with the values resulting from analysis of experimental data. The different kinds of electron transfer estimated on the base of the proposed "additive model" are also strongly supported by calculations.
5
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Electronic and Magnetic Properties of Y(FeV)_{12} Compound and its Carbides

64%
Deniszczyk J., Borgieł W.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
459-462
EN
Electronic and magnetic properties of body centered tetragonal YFe_{8}V_{4} carbon doped compounds were determined by tight-binding linear muffin-tin orbitals method assuming experimental values of lattice constants. Total, partial densities of states and magnetic moments for YFe_{8}V_{4} and its carbides for different positions of carbon within unit cell of parent compound were calculated and discussed. In spite of carbides' unit volume decrease enhancement of magnetization and Curie temperature were obtained. Results are in quantitative agreement with experimental data.
6
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Scalar Relativistic Spin Polarized Electronic Structure of Ferromagnetic fcc GdAl_{2}

64%
Borgieł W., Deniszczyk J.
Acta Physica Polonica A
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1993
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vol. 84
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issue 6
1071-1083
EN
One-particle electronic states of ferromagnetic single crystal Laves phase GdAl_{2} is calculated with the help of augmented spherical waves, based on density functional theory. Density of states, partial densities of states are presented. The behavior of the spectrum in the vicinity of the Fermi energy and the number of occupied states are discussed in detail.
7
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Electronic Structure and Electron-Transport Properties of (Gd_{1-x}Y_{x})_{2}In Compounds

64%
Borgieł W., Deniszczyk J.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
783-786
EN
Based on the electronic structure of the ferromagnetic Gd_{2}In and (Gd_{0.5} Y_{0.5})_{2}In compounds the high-temperature magnetic part of the electrical resistivity of (Gd_{1-x}Y_{x})_{2}In as a function of Y concentration was calculated and analyzed. The main interaction which causes the finite magnetic part of the conductivity was assumed in a form of stochastically distributed in space s-f interaction. The calculated resistivity of (Gd_{1-x}Y_{x})_{2}In alloys qualitatively reproduces the experimental data.
8
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Ab Initio Study of the ^{57}Fe Electric Field Gradient in (FeAl)_{1-x}T_x (T = 3d Element) Dilute Alloys with B2-Type Structure

51%
Michalecki T., Hanc A., Deniszczyk J., Borgieł W.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1483-1491
EN
We present an ab initio study of the electric field gradient at Fe nuclei in the series of (FeAl)_{1-x}T_x dilute alloys with B2-type crystal structure. The ternary additions T, of concentration x ≈ 0.06, from the group of 3d-type transition metals (Ti, V, Cr, Mn, Co, Ni, Cu) are considered. Lattice, local valence electron (3d, 4p) and weakly bound 3p core electron contributions to electric field gradient are separated out and discussed in the context of the T-atom site preference and changes of the electronic structure upon alloying. Contrary to earlier reports, we found that for most Fe nuclei the dominant contribution comes from the d-type valence electrons cancelled partially by the 3p and 4p electric field gradients which are both of opposite sign to that of the 3d one. The shielding effect of 3p semicore electrons is found and related to the electric field gradient contributed by the local valence electrons.
9
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Hyperfine Interaction Parameters in Fe_{28}Al_{72}: ^{57}Fe Mössbauer Spectroscopy and Ab Initio Study

51%
Hanc A., Deniszczyk J., Kansy J.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1154-1155
EN
The paper discusses a theoretical model that associates the shape of the Mössbauer spectrum with the configuration of atoms in local surroundings of the Mössbauer nuclide. Using the model we analyse the Mössbauer spectra of Fe_{72}Al_{28} alloys after various heat treatments. Basing on the model calculations the hyperfine structure parameters describing an effect of an Al atom in the first and the second coordination shell of ^{57}Fe atom are evaluated. Using these parameters the values of hyperfine magnetic field and isomers shift for the atomic configurations present in stoichiometric Fe_3Al are estimated and compared with the results of ab initio calculations.
10
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Resistivity of (Gd_{1-x}Y_{x})_{2}In Alloys at High Temperatures - Two-Band Model Approach

51%
Borgieł W., Deniszczyk J., Lipowczan M., Braun J.
Acta Physica Polonica A
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2000
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vol. 98
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issue 5
547-550
EN
Two-band model for the substitutionary binary alloy of different rare earth metals with relatively simple 4f multiplet structure placed within the transition metal host matrix was proposed and applied to (Gd_{1-x}Y_{x})_{2}In. The main interaction which causes the magnetic part of the resistivity was assumed in a form of stochastically distributed in space s-f interaction. The calculated high temperature spin disorder resistivity of (Gd_{1-x}Y_{x})_{2}In alloys reproduces well the experimental alloys data.
11
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Effect of Alloying on Magnetism and Electronic Structure of Gd(In_{1-x}Snₓ)₃ System - ab initio Study

51%
Deniszczyk J., Bajorek A., Chełkowska G., Zipper E.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
427-429
EN
We present the results of ab initio study of electronic and magnetic properties of Gd(In_{1-x}Snₓ)₃ alloys carried out with the use of FP-LAPW method. Our precise ab initio calculations for the first time uniquelly confirmed experimentally based predictions that the ground state magnetic structure of the alloys is antiferromagnetic and that upon the In/Sn substitution the magnetic structure undergo transition, changing the antiferromagnetic ordering from the (π00)-type for the GdSn₃ compound to the (ππ0)-type for the GdIn₃ one. Moreover, calculations gave an explanation of the oscillatory variation of density of states at Fermi level indicated by XPS measurements.
12
Content available remote

Electrical Conductivity for the Strongly Correlated and Hybridized Hubbard Band

51%
Kosimow R., Borgieł W., Deniszczyk J.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
799-802
EN
The magnetic and electrical transport properties of strongly correlated Hubbard band (f-band) hybridizing with the non-correlated conduction band (c-band) was studied. The many-body model Hamiltonian was treated within the modified alloy analogy scheme and the resulting one-body problem was solved with the use of coherent potential approximation. Within the Kubo-Greenwood formalism the dc electrical conductivity for bcc magnetic system was calculated and its variation with temperature and number of electrons was examined for different values of the Coulomb and hybridization (V) coupling constants. We found that the effect of strong correlations and hybridization on the conductivity is similar to that produced by the scattering due to the s-f interaction (spin disorder resistivity).
13
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Effect of Noncollinear Magnetic Order on the Hyperfine Interactions in Pt_{3}Fe

51%
Woźniakowski A., Deniszczyk J., Szymański K.
Acta Physica Polonica A
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2011
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vol. 119
|
issue 1
65-67
EN
The investigations of the hyperfine interactions in Pt_{3}Fe with the noncollinear magnetic order by means of ab initio methods are presented. It is shown that the ground state magnetic order of Pt_{3}Fe is of noncollinear character. Electric field gradient and hyperfine magnetic field at ^{57}Fe nucleus were calculated and their dependence on the strength of Coulomb correlation interaction is discussed. The calculated values of electric field gradient correspond with the experimental data and the best agreement was found when the enhanced Coulomb correlation interaction for 3d-states of Fe was considered. Lattice, local valence electron (3d, 4p) and weakly bound 3p semicore electron contributions to electric field gradient are separated out and discussed.
14
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Ab Initio Study of Electronic and Magnetic Structure and Structural Phase Transition of (Fe_{1 - x}Mn_{x})_2P_{1 - y}Ge_{y} Alloys

51%
Deniszczyk J., Woźniakowski A., Kolano R., Kolano-Burian A.
|
EN
The paper presents results of the ab initio electronic structure calculations performed for the (Fe_{0.5}Mn_{0.5})_2P_{0.67}Ge_{0.33} alloy, a member of (Fe_{1 - x}Mn_{x})_2P_{1 - y}Ge_{y} family of alloys showing a giant magnetocaloric effect. Calculations confirmed the strong relationship between the magnetic state and crystal structure of the alloy. To investigate the isostructural phase transition driven by external magnetic field observed in (Fe_{0.9}Mn_{1.1})P_{0.8}Ge_{0.2} we utilized the fixed spin moment approach. Total energy analysis confirmed the occurrence of isostructural phase transition.
15
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Magnetic and Electronic Properties of Disordered (Gd_{1 - x}Y_{x})_7Pd_3 Alloys - Theoretical Study

51%
Woźniakowski A., Deniszczyk J., Borgieł W.
|
EN
The ab initio study of electronic and magnetic properties of (Gd_{1 - x}Y_{x})_7Pd_3 alloys are presented. The electronic structure calculations were performed using FP-LAPW method. Basing on the ground-state single-electron results the many particle s-f model for disordered alloy with strongly correlated band electrons was parameterized. The concentration dependence of the band structure, magnetic moment, and the Curie temperature is presented and discussed in reference to experimental data.
16
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Ab Initio Study of Electronic Structure and Magnetic Properties of Gd(Ni_{1-x}Fe_x)_3 Alloys

51%
Deniszczyk J., Woźniakowski A., Borgieł W.
|
EN
We present the ab initio investigations of the electronic and magnetic properties of magnetocaloric Gd(Ni_{1-x}Fe_x)_3 alloys. To simulate fractional concentrations the supercell approach was implemented and different configurations of iron atoms were considered. Energetical analysis of site preference and magnetic order was performed. The concentration dependence of the averaged total and local magnetic moments and of the valence band photoemission spectra are presented and discussed in reference to experimental data.
17
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Electronic Structure of Sm(Ni_{1-x}Co_{x})₃ Alloys - XPS and ab initio Study

45%
Majtyka A., Sikora M., Blachiński D., Chełkowska G., Deniszczyk J.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
673-675
EN
The band structure investigations for Sm(Ni_{1-x}Co_{x})₃ alloys by means of X-ray photoelectron spectroscopy (XPS) and an ab initio density functional theory (DFT) calculations are presented. The aim was to determine an effect of Ni/Co substitution on the electronic structure of the alloys. Investigations have shown that the Ni/Co substitution results in a reconstruction of the valence band (VB), especially the intensity near the Fermi level decreases with Co content. An ab initio simulated XPS VB spectra agree qualitatively with experimental ones with the exception of the Sm-4f sub-spectra where the multiplet decomposition is observed. Calculations shown that variation of magnetization in Sm(Ni_{1-x}Co_{x})₃ is driven mainly by the Ni/Co-3d and Sm-5d states polarization and increases linearly with rising Co content.
18
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Hyperfine Interactions of ^{57}Fe in Pt_3Fe - Ab Initio and Mössbauer Effect Studies

39%
Deniszczyk J., Satuła D., Waliszewski J., Rećko K., Olszewski W., Parzych G., Szymański K.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
197-199
EN
The Mössbauer effect and ab initio investigations of an electric field gradient at ^{57}Fe nuclei in Pt_3Fe compound are presented. It is shown that nonzero ^{57}Fe electric field gradient exists in the cubic Pt_3Fe. Ab initio study of Pt_3Fe in antiferromagnetic state confirms the presence of electric field gradient at ^{57}Fe nuclei. Lattice, local valence electron (3d, 4p) and weakly bound 3p core electron contributions to electric field gradient are separated out and discussed in the context of the electronic structure changes upon the antiferromagnetic phase transition.
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