Search results

1

Electronic Structure and Martensitic Transformation in Ni_{2} MnGa Heusler Alloy

100%

Pugaczowa-Michalska M.

Acta Physica Polonica A

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1999

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vol. 96

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issue 3-4

467-473

EN

The electronic structure of the Ni_{2}MnGa Heusler alloy has been investigated for martensitic transformation β_{1} → β'_{1} → β"_{1} → β'''_{1} by the self-consistent TB-LMTO method. The distortion influences the shape of the densities of states. The β_{1} is the most stable phase. We present the values of total and local magnetic moments for all phases of Ni_{2}MnGa alloy.

2

The Electronic and Magnetic Properties of UGe Compound

63%

Werwiński M., Szajek A.

Acta Physica Polonica A

|

2010

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vol. 118

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issue 5

886-887

EN

The UGe system crystallizes in the orthorhombic ThIn-type structure. The uranium atoms occupy three crystallographic sites with interatomic U-U distances like below and above the Hill limit. The band structure has been calculated by using the density functional theory and generalized gradient approximation. Ab initio calculations were performed based on the full-potential local-orbital minimum-basis code. Calculations showed that all three types of uranium atoms are magnetically ordered with antiparallel alignment of the magnetic moments. For uranium atoms with an interatomic distance below the Hill limit magnetic moments are significantly reduced due to hybridization effects.

3

4f Shell of Gd^{2+} and Gd^{3+} Ions in Sn_{1-x}Gd_{x}Te - Resonant Photoemission Study

63%

Kowalski B. J., Gołacki Z., Guziewicz E., Orłowski B. A., Johnson R. L.

Acta Physica Polonica A

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1997

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vol. 92

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issue 5

875-878

EN

Resonant photoemission spectra of Sn_{1-x}Gd_{x}Te (x=0.02 and 0.08) measured for the photon energy range 142 to 151 eV show the valence band density of states distribution and the Gd 4f derived maximum. The energy position of the J=0 component of the Gd 4f maximum was determined and used as a measure of the Gd 4f shell binding energy. The electrostatic model of core level shifts was used to interpret the difference in the Gd 4f binding energies observed for x=0.02 and x=0.08.

4

The Electronic and Magnetic Properties οf Yb_xGd_{1-x}Ni_5 Systems

63%

Szajek A., Werwiński M., Chełkowska G., Bajorek A., Chrobak A.

Acta Physica Polonica A

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2010

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vol. 118

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issue 5

905-906

EN

The intermetallic compounds Yb_{x}Gd_{1 - x}Ni_5 crystallize in the hexagonal CaCu_5-type structure. Based on wide ranging SQUID-type magnetometer, it was shown that the saturation magnetization decreases with growing concentration of ytterbium. The opposite tendency was observed for the Sommerfeld coefficient obtained in the heat capacity measurements. These results are confirmed using ab initio band structure calculations.

5

Consistency and Symmetry Conditions for Plane Projections

63%

Kontrym-Sznajd G.

Acta Physica Polonica A

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1999

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vol. 95

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issue 4

581-585

EN

Interdependences between plane projections of densities ρ(p) for various crystallographical structures are derived from the conditions of both the consistency and symmetry of projections. Some additional relations are obtained by treating plane projections as line projections of ρ̃_{L}(p) (ρ̃_{L} is a line projection of ρ(p)) and using the consistency and symmetry conditions for the line projections. The relations found can be utilized for both an improvement of experimental spectra and a verification of various techniques used for e.g. correcting Compton profiles.

6

Consistency and Symmetry Conditions for Line Projections

63%

Kontrym-Sznajd G., Jura A.

Acta Physica Polonica A

|

1999

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vol. 95

|

issue 4

586-590

EN

We present some relations between experimental spectra representing line projections of electronic densities in the momentum space. All spectra which are the projections of the same density, must be interdependent. It can be derived from the consistency condition and symmetry of the line projections. The knowledge of these dependences, found in the paper, can be utilised for an improvement of experimental data as e.g. two-dimensional angular correlation of positron annihilation spectra.

7

Reconstruction of Densities from Compton Profiles with Applying Jacobi Polynomials

63%

Kontrym-Sznajd G., Samsel M., West R.

Acta Physica Polonica A

|

1999

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vol. 95

|

issue 4

591-595

EN

The advent of synchrotron sources has led to an increasing availability of high resolution Compton profiles J(p_{z}) and a consequent renewed interest in the reconstruction of the corresponding full momentum densities ρ(p). We present results of applying a new method in which the radial parts of ρ(p) and the measured profiles are expressed in terms of the Jacobi polynomials. The technique is demonstrated using model projections that correspond to Mg and Gd spectra. Reconstructed densities, being in very good agreement with model ones, are a very good performance of our new reconstruction algorithm.

8

Structural, Chemical Bonding, Electronic and Magnetic Properties of XY_{3} (X = Al, Ga and Y = V, Nb, Cr, Mo) Compounds

63%

Hafeez R., Murtaza G., Khenata R., Wong K., Naeem S., Khalid M., Alahmed Z., Bin Omran S.

Acta Physica Polonica A

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2015

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vol. 127

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issue 3

770-779

EN

The metallic behavior of the band gap of intermetallic compounds has large applications in superconductivity, nickel-metal hydrides batteries, semiconductors, and heating materials. The presence of transition elements makes them more attractive for magnetic applications. In this work we studied the structural, electronic, chemical bonding, and magnetic properties of binary intermetallic compounds XY_3 (X = Al, Ga and Y = V, Nb, Cr, Mo). These compounds were investigated by using full potential linearized augmented plane wave plus local orbitals method. The exchange correlation potential of generalized gradient is used. Our calculated lattice constants are in good agreement with experimental values. The band structures of these compounds are purely overlapping across the Fermi level. The bonding is mainly covalent in these compounds. The density of states of the compounds shows that the major contribution arises from d-states of anions. The investigation carried out shows that the most of these compounds have ferromagnetic nature, while few are diamagnetic. On the basis of this study it is expected that these compounds can be used as a best moulds for future study on similar compounds.

9

Electronic Structure of DyCo_5 and DyCo_3B_2 Compounds

63%

Jezierski A., Kowalczyk A.

Acta Physica Polonica A

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2001

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vol. 100

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issue 4

565-572

EN

We study the electronic structure of the hexagonal DyCo_5 and DyCo_3B_2 compounds. The magnetic moments and the band structures were calculated by ab initio self-consistent tight binding linear muffin-tin orbital method within the atomic sphere approximation. These compounds crystallize in a hexagonal structure having the P6/mmm space group. The substitution of cobalt by boron atoms changes the local environment of remaining Co atoms and leads to the decrease in the local magnetic moments as well as in the Curie temperature.

10

Electron Damping in Surface Studies

63%

Bartoš I.

Acta Physica Polonica A

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1992

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vol. 81

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issue 1

33-37

EN

Electron correlation is responsible for finite lifetimes of excited electrons in crystals. Lifetime energy dependence can be obtained for infinite jellium model and only very recently the first results for an infinite crystal have been evaluated (GW approximation). Here, a phenomenological approach, based on Green functions, is presented. Broadening of local densities of electron states as well as that of angular-resolved photoemission (ARUPS) peaks and very-low-energy-electron diffraction (VLEED) profiles, due to the imaginary component of the optical potential is reviewed and interpreted. Anisotropy of electron damping on crystal surfaces has been found in VLEED as a result of electron channeling along the densely packed (111) surface atomic planes in fcc crystals. Interpretation of peak widths in VLEED-and ARUPS-profiles provides a mean to learn about damping of electrons, excited on crystal surface.

11

Electronic Structure and X-Ray Photoemission Spectra of MPtSn ( rm M = Ti, Zr, Hf)

63%

Morkowski J., Szajek A., Chełkowska G., Bajorek A., Troć R.

Acta Physica Polonica A

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2009

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vol. 115

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issue 5

935-940

EN

The electronic structures of the half-Heusler isostructural compounds TiPtSn, ZrPtSn and HfPtSn were calculated and measured applying the X-ray photoemission spectroscopy. The (Ti, Zr, Hf)PtSn compounds have gaps between the occupied valence band and the empty conduction band, calculated as about 0.75, 1.12, and 1.09 eV, respectively. The calculations were done by the full-potential local orbitals method in the framework of the local spin-density approximation and partly also by the full-potential linear muffin-tin orbitals method by the LmtART code. Experimental X-ray photoemission spectra were measured using photons of energy of 1486.6 eV. The experimental and calculated spectra match quite well except a small shift in the energy scale.

12

Electronic Phase Transition in Layered Materials 1T-TaS_{x}Se_{2-x} Probed by Cryogenic STM/STS

63%

Hasegawa T., Shiino O., Yamaguchi W., Endo T., Sugawara H., Kitazawa K.

Acta Physica Polonica A

|

1998

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vol. 93

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issue 2

297-305

EN

A metal-insulator transition, Mott transition, in layered materials 1T-TaS_{x}Se_{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_{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.

13

Magnetic Properties of the U_5Ge_4 Compound Based on Ab initio Calculations

63%

Szajek A., Werwiński M., Malinowski W., Leśniak P.

Acta Physica Polonica A

|

2009

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vol. 115

|

issue 1

251-253

EN

U_5Ge_4 crystallizes in a hexagonal Ti_5Ga_4 type structure with two inequivalent crystallographic sites occupied by uranium atoms. The band structure calculations were performed by the full-potential local-orbital minimum basis band structure code. The calculations showed that on both types of uranium atoms small magnetic moments are formed and their values are equal to 0.08 and 0.15 μ_{B}/atom, respectively.

14

The Electronic and Electrochemical Properties of the LaNi_5-Based Alloys

63%

Szajek A., Jezierski A., Nowak M., Jurczyk M.

Acta Physica Polonica A

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2009

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vol. 115

|

issue 1

247-250

EN

Mechanical alloying was used to synthesize LaNi_5-type hydrogen storage materials. X-ray diffraction analysis showed that, after 30 h milling, the starting mixture of the elements was decomposed into an amorphous phase. Following the annealing in high purity argon at 700°C for 0.5 h, X-ray diffraction confirmed the formation of the CaCu_5-type structures. The nanocrystalline materials were used as negative electrodes for a Ni-MH_x battery. A partial substitution o Ni by Al or Mn in LaNi_{5-x}M_x alloy leads to an increase in discharge capacity. On the other hand, the alloying elements such as Al, Mn and Co greatly improved the cycle life of LaNi_5 material. For example, in the nanocrystalline LaNi_{3.75}Mn_{0.75}Al_{0.25}Co_{0.25} powder, discharge capacities of up to 258 mA h g^{-1} (at 40 mA g^{-1} discharge current) were measured. The band structure ab initio calculations showed that 3g sites are preferred by Al, Co, and Mn atoms in the unit cell.

15

Electronic Structure and Magnetic Properties οf the UCoAs_{2} Compound

63%

Werwiński M., Szajek A.

Acta Physica Polonica A

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2009

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vol. 115

|

issue 1

244-246

EN

The UCoAs_{2} compound crystallizes in the tetragonal HfCuSi_{2} type structure with space group P4/nmm. The compound orders ferromagnetically at 150 K with a spontaneous magnetic moment of about 1.8 μ_B per formula unit. We present results of fully relativistic band structure calculations based on the full-potential local-orbital minimum-basis scheme (FPLO-5.10-20) and compare magnetic moments obtained from calculations without and with orbital polarization corrections. The magnetic behavior of the Co atoms remains unknown.

16

Band Gap Stability in Kondo Insulators

63%

Ślebarski A., Jezierski A., Zygmunt A.

Acta Physica Polonica A

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2000

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vol. 97

|

issue 1

59-70

EN

We report on magnetic measurements and electronic structure investigations of CeNiSn and CeRhSb. Both belong to the group of Kondo insulators. The magnetic susceptibility shows the nonmagnetic ground state for these compounds and their alloys. The 3d X-ray photoemission spectroscopy spectra show evidence for the mixed valence state of Ce in CeRhSb alloys, as also seen for CeNiSn, whereas the spectra for the La substituted (Ce,La)NiSn compounds show only evidence for a pure Ce^{3+} ground state. We suggest the presence of Kondo-hole states in (Ce,La)RhSb. The location of the pseudogap in CeRhSb varies with the number of free electron, the valence of Ce, and the f-d hybridization. We discuss the similar crystallographic properties and the closed electronic structures of ZrNiSn-type semi-Heusler alloys and CeNiSn-type Kondo insulators.

17

Topographic and Energetic Heterogeneity Studies of Oxidized Graphite Surface by Scanning Tunneling Microscopy/Spectroscopy and Photoelectron Spectroscopy

63%

Klusek Z.

Acta Physica Polonica A

|

1997

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vol. 91

|

issue 3

569-582

EN

Scanning tunneling microscopy and spectroscopy and X-ray photoelectron spectroscopy are used to study oxidation effects of nitric acid on a highly-oriented pyrolytic graphite surface. Various etching times at constant temperature are applied in order to create local binding sites on the surface without creating deep defects. A single and paired chains structure, different from pure graphite at atomic scale, is shown by scanning tunneling microscopy. This can be explained by the presence of oxygenate groups on the surface, revealed by X-ray photoelectron spectroscopy. Both scanning tunneling spectroscopy and X-ray photoelectron spectroscopy demonstrate the vanishing of π bands characteristic of sp^{2} graphite hybridization. This, in turn, can be explained by dehybridization related to new bondings of the graphite carbons in the oxygenate groups. An important result of area averaging spectroscopy is the observed energetic heterogeneity considered in terms of the changes of local electronic density of states of the oxidized surface.

18

Electronic Structure and Magnetic Properties of Ce_5CuPb_3 Based on Ab Initio Calculations

63%

Werwiński M., Szajek A., Leśniak P., Malinowski W., Stasiak M.

Acta Physica Polonica A

|

2012

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vol. 121

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issue 5-6

1182-1184

EN

Ce_5CuPb_3 band structure has been calculated based on two ab initio methods: full potential-linearized augmented plane wave implemented in WIEN2k code and full-potential local-orbital minimum-basis in FPLO code. The calculations were performed with and without spin polarization. Starting from the generalized gradient approximation we additionally tested either an orbital polarization correction and the GGA+U approach with the Coulomb repulsion energies U varied from 0 to 6.7 eV within the Ce 4f electron shell. The calculations confirmed possible antiparallel alignment of the magnetic moments of the cerium atoms in the low temperature phase.

19

Effect of Al Substitution on the Electronic and Magnetic Properties of GdCo_5

63%

Szajek A., Malinowski W.

Acta Physica Polonica A

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2002

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vol. 101

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issue 4

525-536

EN

Experimental data show that aluminium doped RCo_5 systems crystallize in CaCu_5-type structure for most of the rare-earth elements (R). Al impurities randomly occupy one of the two possible positions (2c and 3g) and there is a critical concentration of Al, x_c=2.0, for RCo_{5-x}Al_x when the Co sublattice becomes nonmagnetic. The ab initio self-consistent calculations show strong dependence of magnetic properties of GdCo_{5-x}Al_x on concentration of Al and position of the impurities in the unit cell, furthermore to fulfil experimental observation of existence of critical concentration, x_c=2.0, the Al impurities should prefer 3g positions otherwise the magnetic moments on Co atoms do not vanish.

20

The Electronic and Magnetic Properties of the USn_2 Compound

63%

Szajek A.

Acta Physica Polonica A

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2004

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vol. 105

|

issue 5

485-493

EN

The ab initio self-consis tent calculations were performed for USn_2 compound, which crystallizes in the ZrGa_2-type structure (Cmmm space group). The tight binding linear muffin-tin orbital method in the atomic sphere approximation was used in the calculations. The spin-polarized calculations confirmed the antiferromagnetic order in the USn_2 system. The magnetic moment is predominantly located on the uranium atoms and is formed mainly by the f electrons. The three types of Sn atoms may be treated as non-magnetic.

Refine search results

Electronic Structure and Martensitic Transformation in Ni_{2} MnGa Heusler Alloy

The Electronic and Magnetic Properties of UGe Compound

4f Shell of Gd^{2+} and Gd^{3+} Ions in Sn_{1-x}Gd_{x}Te - Resonant Photoemission Study

The Electronic and Magnetic Properties οf Yb_xGd_{1-x}Ni_5 Systems

Consistency and Symmetry Conditions for Plane Projections

Consistency and Symmetry Conditions for Line Projections

Reconstruction of Densities from Compton Profiles with Applying Jacobi Polynomials

Structural, Chemical Bonding, Electronic and Magnetic Properties of XY_{3} (X = Al, Ga and Y = V, Nb, Cr, Mo) Compounds

Electronic Structure of DyCo_5 and DyCo_3B_2 Compounds

Electron Damping in Surface Studies

Electronic Structure and X-Ray Photoemission Spectra of MPtSn ( rm M = Ti, Zr, Hf)

Electronic Phase Transition in Layered Materials 1T-TaS_{x}Se_{2-x} Probed by Cryogenic STM/STS

Magnetic Properties of the U_5Ge_4 Compound Based on Ab initio Calculations

The Electronic and Electrochemical Properties of the LaNi_5-Based Alloys

Electronic Structure and Magnetic Properties οf the UCoAs_{2} Compound

Band Gap Stability in Kondo Insulators

Topographic and Energetic Heterogeneity Studies of Oxidized Graphite Surface by Scanning Tunneling Microscopy/Spectroscopy and Photoelectron Spectroscopy

Electronic Structure and Magnetic Properties of Ce_5CuPb_3 Based on Ab Initio Calculations

Effect of Al Substitution on the Electronic and Magnetic Properties of GdCo_5

The Electronic and Magnetic Properties of the USn_2 Compound