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Wyświetlanie 1-15 z 42
Tytuł:
Solid State Ion Exchange Reactions of Co with Zeolites
Autorzy:
Jentys, A.
Lugstein, A.
Vinek, H.
Powiązania:
https://bibliotekanauki.pl/articles/1964135.pdf
Data publikacji:
1997-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Bw
82.65.Jv
71.20.Be
81.20.Fw
61.10.Ht
71.20.Ps
Opis:
Co cations were introduced into ZSM5 and faujasite type zeolites by solid state ion exchange. On both types of zeolites the solid state reaction led to an exchange of all protons. On ZSM5 one proton was exchanged with one Co$\text{}^{2+}$ cation, while on the faujasite samples two protons were exchanged with one Co$\text{}^{2+}$ cation. After the incorporation of cobalt two new Lewis acid sites were observed on the CoZSM5 and CoY samples.
Źródło:
Acta Physica Polonica A; 1997, 91, 5; 969-974
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Study of Substitution of Si for Ge in Mn$\text{}_{5}$Ge$\text{}_{3}$
Autorzy:
Siberchicot, B.
Henrion, R.
Toboła, J.
Powiązania:
https://bibliotekanauki.pl/articles/1956494.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Be
75.50.Cc
75.10.Lp
Opis:
The substitution of silicon for germanium in Mn$\text{}_{5}$Ge$\text{}_{3}$ leads to a decrease in the magnetization for x < 0.7 and then to phase transition toward a non-collinear antiferromagnetic order for Mn$\text{}_{5}$Si$\text{}_{3}$. The magnetic properties of Mn$\text{}_{5}$Ge$\text{}_{3}$ and Mn$\text{}_{5}$(Ge$\text{}_{0.5}$Si$\text{}_{0.5}$)$\text{}_{3}$ are analyzed by means of band structure calculations.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 467-470
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of Core-Hole Screening on Spin-Polarised Auger Spectra from Ferromagnetic Ni
Autorzy:
Wegner, T.
Potthoff, M.
Nolting, W.
Powiązania:
https://bibliotekanauki.pl/articles/2013223.pdf
Data publikacji:
2000-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.20.Fv
71.20.Be
75.60.Ej
Opis:
We calculate the spin- and temperature-dependent local density of states for ferromagnetic Ni in the presence of a core hole at a distinguished site in the lattice. Correlations among the valence electrons and between valence and core electrons are described within a multi-band Hubbard model which is treated by means of second-order perturbation theory around the Hartree-Fock solution. The core-hole potential causes strong screening effects in the Ni valence band. The local magnetic moment is found to be decreased by a factor of 5-6. The consequences for the spin polarisation of CVV Auger electrons are discussed.
Źródło:
Acta Physica Polonica A; 2000, 97, 3; 567-570
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Studies of S=1 Heisenberg Planar Antiferromagnetic Chain Ni(C$\text{}_{11}$H$\text{}_{10}$N$\text{}_{2}$O)$\text{}_{2}$Ni(CN)$\text{}_{4}$
Autorzy:
Čizmár, E.
Černák, J.
Orendáč, M.
Herrmannsdörfer, T.
Feher, A.
Powiązania:
https://bibliotekanauki.pl/articles/2013230.pdf
Data publikacji:
2000-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
71.20.Be
75.50.Ee
Opis:
In this paper we discuss the results of experimental studies of specific heat and magnetic susceptibility of chain compound Ni(C$\text{}_{11}$H$\text{}_{10}$N$\text{}_{2}$O)$\text{}_{2}$Ni(CN)$\text{}_{4}$. We have observed a Schottky type anomaly at T=2.2 K in a temperature dependence of specific heat and the compound was identified as a S=1 Heisenberg antiferromagnetic chain with the subcritical exchange coupling D/k$\text{}_{B}$=5 K, D/|J|=5.2 and the strong in-plane anisotropy E/k$\text{}_{B}$=2.8 K. It has been found that the in-plane anisotropy affects the region of validity of a diluted exciton model [1] and a strong coupling model [2] for S=1 Heisenberg chains with the strong planar anisotropy. The analysis suggests that the in-plane anisotropy should be considered in any attempt to find a compound potentially located in the boundary of Haldane and "large-D" phases.
Źródło:
Acta Physica Polonica A; 2000, 97, 3; 579-582
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Local Environment on the Electronic Structure and Magnetic Properties of Ni$\text{}_{1-x}$Cu$\text{}_{x}$MnSb Alloys
Autorzy:
Jezierski, A.
Szytuła, A.
Powiązania:
https://bibliotekanauki.pl/articles/2013241.pdf
Data publikacji:
2000-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.15.Ar
31.15.Ew
71.15.Mb
71.15.-m
71.15.La
71.20.-b
71.20.Be
Opis:
The magnetic ordering in Ni$\text{}_{1-x}$Cu$\text{}_{x}$MnSb alloys changes from ferromagnetic (x=0) to antiferromagnetic (x=1). The X-ray and neutron diffraction showed that the systems crystallise in C1$\text{}_{b}$ type structure. We present an influence of the local chemical ordering on the electronic and magnetic properties of Ni$\text{}_{1-x}$Cu$\text{}_{x}$MnSb alloys. The band structure and the magnetic moments were calculated by the spin-polarised linear muffin-tin orbital in the atomic sphere approximation method for the experimental values of the lattice parameters. The magnetic moment of Mn increases from 3.8 μ$\text{}_{B}$ for x=0 to 4.18 μ$\text{}_{B}$ for x=1.
Źródło:
Acta Physica Polonica A; 2000, 97, 3; 607-610
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Small Pt Doping on the Electronic Structure of NiMnSb Half-Heusler Alloys
Autorzy:
Pugaczowa-Michalska, M.
Powiązania:
https://bibliotekanauki.pl/articles/2035739.pdf
Data publikacji:
2003-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
71.20.Be
75.50.-y
Opis:
The effect of small Pt doping on the electronic and magnetic properties of NiMnSb compound were studied using the spin-polarised tight-binding linear muffin-tin orbital method. The electronic structure of half-Heusler alloys depends on the relative arrangement of the atoms in the unit cell, changing from half-metal to metal. The local ordering drastically influences the value of the band gap. The self-consistent band calculations were performed for the experimental lattice constant and for the lattice parameter estimated from the minimum of the total energy.
Źródło:
Acta Physica Polonica A; 2003, 103, 4; 393-402
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Correlations within Fermionic Lattice Models
Autorzy:
Matlak, M.
Grabiec, B.
Krawiec, S.
Powiązania:
https://bibliotekanauki.pl/articles/2047738.pdf
Data publikacji:
2007-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.-w
71.10.Ca
71.10.Fd
71.20.Be
71.27.+a
71.28.+d
73.21.La
78.67.Bf
Opis:
We investigate two-site electronic correlations within generalized Hubbard model, which incorporates the conventional Hubbard model (parameters: t (hopping between nearest neighbours), U (Coulomb repulsion (attraction))) supplemented by the intersite Coulomb interactions (parameters: J$\text{}^{(1)}$ (parallel spins), J$\text{}^{(2)}$ (antiparallel spins)) and the hopping of the intrasite Cooper pairs (parameter: V). As a first step we find the eigenvalues E$\text{}_{α}$ and eigenvectors |E$\text{}_{α}$〉 of the dimer and we represent each partial Hamiltonian E$\text{}_{α}$|E $\text{}_{α}$〉〈 E$\text{}_{α}$| (α=1,2,...,16) in the second quantization with the use of the Hubbard and spin operators. Each dimer energy level possesses its own Hamiltonian describing different two-site interactions which can be active only in the case when the level will be occupied by the electrons. A typical feature is the appearance of two generalized t-J interactions ascribed to two different energy levels which do not vanish even for U=J$\text{}^{(1)}$=J{(2)}=V=0 and their coupling constants are equal to ±t in this case. In the large linebreak U-limit for J$\text{}^{(1)}$=J$\text{}^{(2)}$=V=0 there is only one t-J interaction with coupling constant equal to 4t$\text{}^{2}$/|U| as in the case of a real lattice. The competition between ferromagnetism, antiferromagnetism and superconductivity (intrasite and intersite pairings) is also a typical feature of the model because it persists in the case U=J$\text{}^{(1)}$=J$\text{}^{(2)}$=V=0 and t≢0. The same types of the electronic, competitive interactions are scattered between different energy levels and therefore their thermodynamical activities are dependent on the occupation of these levels. It qualitatively explains the origin of the phase diagram of the model. We consider also a real lattice as a set of interacting dimers to show that the competition between magnetism and superconductivity seems to be universal for fermionic lattice models.
Źródło:
Acta Physica Polonica A; 2007, 112, 3; 537-547
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetoluminescence Studies of GaN:Fe
Autorzy:
Niedźwiadek, A.
Wysmołek, A.
Wasik, D.
Potemski, M.
Szczytko, J.
Kamińska, M.
Twardowski, A.
Łucznik, B.
Pastuszka, B.
Grzegory, I.
Powiązania:
https://bibliotekanauki.pl/articles/2047373.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Et
71.55.Eq
71.20.Be
Opis:
We report on magneto-optical studies on iron doped GaN crystals grown using hydride vapor phase epitaxy method on bulk GaN substrate. The investigated samples showed an intensive 1.3 eV luminescence band, characteristic of Fe$\text{}^{3+}$(d$\text{}^{5}$) center in GaN. A high quality of the investigated samples allowed us to observe a well-resolved fine structure of intracenter transitions between $\text{}^{4}$T$\text{}_{1}$(G) and $\text{}^{6}$A$\text{}_{1}$(S) states, consisting of four sharp no-phonon lines. All the observed no-phonon lines showed pronounced splittings in magnetic field. From the analysis of the magneto-optical data, the structure of split $\text{}^{4}$T$\text{}_{1}$(G) multiplet in the magnetic field applied along c-axis of GaN crystals was established.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 177-182
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Surface Investigations of Selected Materials by Low-Energy Ion Scattering Technique
Autorzy:
Goc-Jagło, D.
Sitko, D.
Jagło, G.
Kim-Ngan, N.-T. H.
Soszka, W.
Powiązania:
https://bibliotekanauki.pl/articles/2047339.pdf
Data publikacji:
2007-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.35.Rh
71.20.Be
71.20.Eh
77.80.Bh
Opis:
Surfaces of three selected materials were investigated by means of low-energy ion-scattering technique: (1) the magnetite (Fe$\text{}_{3}$O$\text{}_{4}$) exhibiting the so-called Verwey transition (T$\text{}_{V}$(bulk)=125 K) accompanied by a small cubic-monoclinic crystal distortion, (2) the intermetallic compound NdMn$\text{}_{2}$ undergoing an antiferromagnetic-paramagnetic phase transition (T$\text{}_{N}$=104 K) accompanied by a large crystal distortion with a volume change of 1%, and (3) the typical insulator BaTiO$\text{}_{3}$ with two structural transitions below 300 K. The primary energy of the (Ne$\text{}^{+}$, Ar$\text{}^{+}$) ion beam was in the range of 4-8 keV, and the low-energy ion-scattering spectra were collected in the temperature range of 85-300 K. A large influence from the Verwey transition on the neutralization and re-ionization of scattered ions from magnetite surface was observed, while no visible change at the magnetic phase transition in NdMn$\text{}_{2}$ was revealed in the low-energy ion-scattering spectra. A strong dependence of the characteristics of the low-energy ion-scattering spectra on the irradiated time was observed for BaTiO$\text{}_{3}$ indicating that this surface was heavily charged by ion bombardments.
Źródło:
Acta Physica Polonica A; 2007, 111, 5; 763-771
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ab Initio Study of the $\text{}^{57}Fe$ Electric Field Gradient in $(FeAl)_{1-x}T_x$ (T = 3d Element) Dilute Alloys with B2-Type Structure
Autorzy:
Michalecki, T.
Hanc, A.
Deniszczyk, J.
Borgieł, W.
Powiązania:
https://bibliotekanauki.pl/articles/1811576.pdf
Data publikacji:
2008-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Be
71.20.Lp
75.50.Bb
76.80.+y
Opis:
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.
Źródło:
Acta Physica Polonica A; 2008, 114, 6; 1483-1491
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characterization of Bimetallic Systems with UPS and PAX: Gold on Platinum and Palladium Surfaces
Autorzy:
Moors, M.
Kobiela, T.
Krupski, A.
Becker, C.
Wandelt, K.
Powiązania:
https://bibliotekanauki.pl/articles/1811505.pdf
Data publikacji:
2008-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
79.60.Bm
73.61.At
71.20.Be
71.20.Eh
71.20.Gj
Opis:
In the present study the thermal behavior of ultrathin Au films deposited on different noble metal single crystal surfaces was studied by means of ultraviolet photoelectron spectroscopy and photoemission of adsorbed xenon. The primary goal of this work was to demonstrate the power of photoemission of adsorbed xenon as an easy to handle and very surface sensitive technique for the characterization of multi-component systems. All investigated systems, Au-Pt(111), Au-Pd(111) and Au-Pd(110) show a particular dependence of their electronic and structural properties on the annealing temperature. Au multilayer films with a thickness of 3 monolayer prepared at 150 K undergo in all cases a smoothening by annealing up to room temperature. While on Pd this effect is mainly detectable on the topmost atomic layer the ordering process on Pt is also affecting the deeper layers. Further annealing of the Au-Pd system to 450 K and the Au-Pt system to 750 K, respectively, results in the onset of the alloying process at the interface between metal film and substrate. After annealing to 650 and 950 K, respectively, the alloying finally extends to the very surface. The complete loss of Au from the surface can be detected at 1050 K on Pd and at 1150 K on Pt. The orientation of the substrate has only a weak influence, showing up e.g. in additional electronic states of the not alloyed Au-Pd(111) and Au-Pd(111) systems. Adsorption of CO as a probe molecule illustrates the formation of different adsorption sites on the bimetallic systems during the Au diffusion process.
Źródło:
Acta Physica Polonica A; 2008, 114, S; S-77-S-92
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative Study of Compressibility of $Ni_2MnX$ (X=In, Sn, Sb) Heusler Alloys
Autorzy:
Pugaczowa-Michalska, M.
Powiązania:
https://bibliotekanauki.pl/articles/1813962.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
71.20.Be
75.20.En
75.50.Cc
Opis:
The present study is focused on the compressibility of $Ni_2MnX$ (X = In, Sn, Sb) Heusler alloys, which were investigated from the first principles. The study of the pressure effect on the magnetic properties of $Ni_2MnX$ (X = In, Sn, Sb) predicted the decrease in the total magnetic moment from ambient pressure to pressure above 20 GPa.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 629-632
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Electronic Structure and Specific Heat of $YNi_4Si$
Autorzy:
Pugaczowa-Michalska, M.
Falkowski, M.
Kowalczyk, A.
Timko, M.
Reiffers, M.
Mihalik, M.
Šebek, J.
Šantava, E.
Powiązania:
https://bibliotekanauki.pl/articles/1813671.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Be
71.20.-b
65.40.-b
Opis:
The studies of the electronic structure and the specific heat of $YNi_4Si$ are reported. Below the Fermi energy $(E_F)$ the density of states contains mainly the 3d states of Ni, which hybridized with 4d states of Y and 3p states of Si. The theoretical electronic specific heat coefficient (12.32 mJ/(mol $K^2$)) obtained for equilibrium lattice parameters and the experimental value (13 mJ/(mol $K^2$)) are in a reasonable agreement.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 323-326
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic and Magnetic Properties of $Co_{3}V_{2}O_{8}$ Compound
Autorzy:
Jezierski, A.
Szymczak, R.
Szymczak, H.
Kaczkowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1810487.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
71.15.-m
71.15.Ap
71.15.Mb
71.20.Be
Opis:
The band structures and the magnetic properties of $Co_{3}V_{2}O_{8}$ compound have been calculated by ab initio scalar-relativistic full potential local orbital method within the local spin density approximation. The band calculations were performed for para-, ferro-, and antiferromagnetic $Co_{3}V_{2}O_{8}$ compounds. The main contribution to the density of states at the Fermi energy comes from minority 3d states of cobalt atoms.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 238-240
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Structure and Magnetic Properties of $Ni_2MnGa_{1-x}Ge_{x}$ and Disordered $Ni_{2}MnSn$ Heusler Alloys
Autorzy:
Pugaczowa-Michalska, M.
Jezierski, A.
Dubowik, J.
Kaczkowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1810489.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
71.20.Be
71.20.-b
Opis:
In this work we present the influence of atomic disorder on the electronic and magnetic properties of $Ni_{2}MnGa_{1-x}Ge_{x}$ and $Ni_{2}MnSn$ Heusler alloys. Ab initio band calculations were performed for the experimental lattice parameters. We applied SPR-KKR-CPA methods in the local spin density approximation.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 241-243
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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