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Wyświetlanie 1-15 z 45
Tytuł:
Hybridization Effects in UCu$\text{}_{5-x}$Au$\text{}_{x}$ Compounds
Autorzy:
Tran, V. H.
Troć, R.
Powiązania:
https://bibliotekanauki.pl/articles/1929857.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
Opis:
We review the results of bulk and neutron diffraction measurements on the UCu$\text{}_{5-x}$Au$\text{}_{x}$ system crystallizing in the cubic AuBe$\text{}_{5}$-type structure. The observed properties may be understood in the light of competition between Kondo effect and RKKY exchange interactions. Effects of 5f-ligand hybridization between the U-atoms occupying the 4a-sites and the Au- or/and Cu-atoms placed at the 4c- and 16e-positions, respectively, are supposed to be different. We show that the prefential occupation of 4c-sites by Au has a marked effect on the magnetic properties of the investigated system.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 287-292
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transport and Magnetic Properties of Pb$\text{}_{1-x}$Mn$\text{}_{x}$Te Doped with Cr and Mo
Autorzy:
Artamkin, A. I.
Kozhanov, A. E.
Arciszewska, M.
Dobrowolski, W. D.
Story, T.
Slynko, E. I.
Slynko, V. E.
Khokhlov, D. R.
Powiązania:
https://bibliotekanauki.pl/articles/2038231.pdf
Data publikacji:
2004-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
Opis:
Transport and magnetic properties of Pb$\text{}_{1-x}$Mn$\text{}_{x}$Te (x<0.18) semiconductor alloys doped with Cr or Mo are investigated in a broad range of temperatures and magnetic fields. In PbMnTe(Cr) alloys the Fermi level may be pinned either in the conduction band or in the energy gap, depending on Mn concentration. In PbMnTe(Mo) alloys the pinning of the Fermi level is observed in the valence band as well as in the energy gap. In the latter case persistent photoconductivity is observed at low temperatures. The analysis of the temperature dependence of magnetic susceptibility shows that PbMnTe alloys doped with Cr or Mo are Curie-Weiss paramagnets revealing weak antiferromagnetic interactions between magnetic ions.
Źródło:
Acta Physica Polonica A; 2004, 106, 2; 223-231
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic-Form Factor Measurements by Polarised Neutron Scattering: Application to Heavy Fermion Superconductors
Autorzy:
Neumann, K.-U.
Ziebeck, K. R. A.
Powiązania:
https://bibliotekanauki.pl/articles/1929383.pdf
Data publikacji:
1993-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.25.+z
71.28.+d
Opis:
The experimental technique of spin polarised neutron scattering as used in magnetic form factor measurements is presented. An introduction to the interpretation and the calculation of magnetic form factors and magnetization densities is given. The experimental technique of neutron scattering theory as applied to elastic spin polarised scattering experiments is briefly introduced. The calculation of the magnetic form factor and the magnetization densities are considered for simple model systems such as a collection of localised magnetic moments or an itinerant electron system. The discussion is illustrated by an experimental investigation of the magnetic form factor in the heavy fermion superconductors UBe$\text{}_{13}$ and UPt$\text{}_{3}$. Magnetization density maps and magnetic form factors are presented, and their implications for other physical quantities are briefly discussed.
Źródło:
Acta Physica Polonica A; 1993, 84, 1; 43-81
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strongly Correlated Electrons in a Magnetic Field: Fermi Liquid versus Spin Liquid
Autorzy:
Spałek, J.
Wójcik, W.
Powiązania:
https://bibliotekanauki.pl/articles/1930575.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.-d
75.10.Lp
Opis:
We compare the Fermi liquid (FL) and statistical spin liquid (SSL) representations of the electronic properties for strongly correlated systems. In particular, we discuss the entropy, as well as the magnetization as a function of band filling, temperature and magnetic field. These properties are quite different in the two (FL, SSL) states. Antiferromagnetic state disappears for a small number of holes in the doped Mott insulator.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 357-361
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low Temperature Transport and Magnetic Properties of SmB$\text{}_{6}$
Autorzy:
Gabani, S.
Flachbart, K.
Pavlík, V.
Konovalova, E.
Paderno, Y.
Herrmannsdörfer, T.
Powiązania:
https://bibliotekanauki.pl/articles/2013029.pdf
Data publikacji:
2000-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Hr
71.28.+d
Opis:
We present results of transport and magnetic properties of three single-crystalline samples of the intermediate valence small-gap semiconductor SmB$\text{}_{6}$ at low temperatures. The received resistivity dependences of the samples below 0.5 K exhibit an activated behavior with an energy gap of a few mK. The temperature dependences of the magnetic susceptibility show an increase below 15 K which can be accounted for by impurities, by bare Sm$\text{}^{3+}$ ions or by a small amount of in-gap magnetic 4f$\text{}^{5}$5d$\text{}^{1}$ states.
Źródło:
Acta Physica Polonica A; 2000, 97, 3; 419-422
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of $UFe_{2+x}$ Prepared by Splat Cooling
Autorzy:
Havela, L.
Miliyanchuk, K.
Pešička, J.
Gonçalves, A.
Waerenborgh, J.
Pereira, L.
Šantavá, E.
Šebek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1813628.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
75.50.Bb
Opis:
A series od $UFe_{2+x}$ materials was prepared using splat cooling. The Laves phase structure can accommodate up to 0.3 Fe excess, while $T_C$ is enhanced from 172 K to approximately 240 K. Higher Fe concentration leads to the segregation of α-Fe. $\text{}^{57}Fe$ Mössbauer spectroscopy indicates higher Fe magnetic hyperfine fields on Fe nuclei occupying the U sublattice than for the regular Fe sites.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 247-250
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
First-Principles Study of Kondo Insulator $SmB_{6}$
Autorzy:
Gmitra, M.
Čenčariková, H.
Farkašovský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1369765.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
71.20.-b
71.27.+a
Opis:
We applied the Perdew-Burke-Ernzerhof hybrid functional (PBE0) within the density functional theory (DFT) to study electronic properties of the heavy fermion Kondo semiconductor $SmB_{6}$. The calculation of the Hartee-Fock exchange contribution to the exact-exchange within the atomic sphere approximation for bulk $SmB_{6}$ represents a computationally efficient, parameter-free method that provides good qualitative and quantitative agreement with photoemission experiments. Specifically, we found an energy difference of 7 eV between the occupied and unoccupied correlated Sm f states. Furthermore, the spin-orbit coupling yields a splitting of the occupied Sm f states of about 1 eV in agreement with recent angular resolved photoemission spectroscopy. The electronic spectrum in the vicinity of the X point shows a hybridization between the Sm 5d conduction band and the localized Sm 4f states at the Fermi level. This might lead to a transport gap opening.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 298-299
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vertex Corrections to the Electrical Conductivity of the Disordered Falicov-Kimball Model
Autorzy:
Pokorný, V.
Janiš, V.
Powiązania:
https://bibliotekanauki.pl/articles/1534607.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
71.28.+d
72.10.Fk
Opis:
Quantum coherence of elastically scattered lattice fermions is studied. We calculate vertex corrections to the electrical conductivity of electrons scattered either on thermally equilibrated or statically distributed random impurities and we demonstrate that the sign of the vertex corrections to the Drude conductivity is in both cases negative.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 922-923
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Mixed Valence State of $Sm_{1-x}B_{6}$ and $Sm_{1-x}La_{x}B_{6}$ by XANES
Autorzy:
Gabáni, S.
Flachbart, K.
Bednarčík, J.
Welter, E.
Filipov, V.
Shitsevalova, N.
Powiązania:
https://bibliotekanauki.pl/articles/1371509.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Dm
71.28.+d
71.27.+a
Opis:
We investigated the valence states of samarium ions in Sm deficient $Sm_{1-x}B_{6}$ (x=0.03, 0.05, 0.08, 0.1 and 0.2) sintered samples, in single crystalline solid solutions $Sm_{1-x}La_{x}B_{6}$ (x=0.16, 0.28, 0.4, 0.55 and 0.7) as well as in a $SmB_{6}$ single crystal by X-ray absorption near edge structure (XANES) between 4.2 and 300 K. It was shown that the mixed valence state $v_{Sm}$ of Sm-ions ($v_{Sm}$ ≈ 2.51 for $SmB_{6}$ at 4.2 K) in deficient samples is changed but maintained up to a concentration of 20% of vacancies and up to a concentration of 70% in samples doped with trivalent La-ions, and that in both cases it increases with temperature. On the other hand, the value of $v_{Sm}$ increases with increasing vacancy level, whereas it decreases with increasing $La^{3+}$ substitution. The obtained dependences of Sm-valence in $SmB_{6}$ on vacancy as well as on $La^{3+}$ ion concentration are in good agreement with susceptibility measurements and exact numerical calculation of the spinless Falicov-Kimball model in two dimensions.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 338-339
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron Correlation Phenomena in Selected Transition Metal Oxides
Autorzy:
Honig, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/1860849.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
71.30.+h
75.10.Lp
Opis:
The theory of electron correlation phenomena is reviewed and used to interpret the transport, thermal, or magnetic properties of V_{2}O_{3}, LaNiO_{3} and Fe_{3}O_{4} systems, each of which to a greater or lesser degree displays correlation effects. A rationale is provided for interpreting the various types of phase transitions encountered in the vanadium sesquioxide and magnetite host systems and to show why these are altered by small compositional variations.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 53-77
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground States of the Falicov-Kimball Model Extended by Nonlocal Coulomb Interactions
Autorzy:
Čenčariková, H.
Farkašovský, P.
Žonda, M.
Powiązania:
https://bibliotekanauki.pl/articles/1813654.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Lp
71.27.+a
71.28.+d
Opis:
The small-cluster exact-diagonalizations are used to study the ground states of the Falicov-Kimball model extended by nonlocal Coulomb interactions (the nearest-neighbour interaction $U_{nn}$ and the correlated hopping t'). It is shown that the ground-state phase diagrams found for the conventional Falicov-Kimball model are strongly changed when the nonlocal interactions are added. This is illustrated for two selected values of the on-site Coulomb interaction (U) that represent typical behaviours of the model in the intermediate and strong coupling limit. A number of remarkable results are found. (i) The phase separation takes place for a wide range of $U_{nn}$ and t' in both interaction limits. (ii) New types of inhomogeneous charge ordering are observed for nonzero $U_{nn}$ and t'. (iii) Depending on the values of $U_{nn}$ and t', the model is able to describe both the continuous as well as discontinuous changes of the f-electron occupation number.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 287-290
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermoelectric Power of $CeNi_4Si$ and $YbNi_4Si$ Compounds
Autorzy:
Falkowski, M.
Kowalczyk, A.
Tran, V.
Miiller, W.
Powiązania:
https://bibliotekanauki.pl/articles/1813661.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
72.20.Pa
71.28.+d
Opis:
The thermoelectric power was measured from 4.2 to 300 K for $CeNi_4Si$ and $YbNi_4Si$. The thermoelectric power was analysed in the framework of the phenomenological resonance model. According to the model the dominant contribution to thermopower is caused by scattering between electrons of a broad s-band and a narrow f-band with the Lorentzian shape. The electron-hole analogy is reflected in the thermoelectric power behaviour of the investigated compounds.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 303-306
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground States of the Spin-One-Half Falicov-Kimball Model with Hunds Rule Coupling in Two Dimensions
Autorzy:
Čenčariková, H.
Farkašovský, P.
Tomašovičová, N.
Žonda, M.
Powiązania:
https://bibliotekanauki.pl/articles/1810314.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Lp
71.27.+a
71.28.+d
Opis:
The spin-one-half Falicov-Kimball model with spin-dependent on-site interaction between localized (f) and itinerant (d) electrons is studied by small-cluster exact-diagonalization calculations and a well-controlled approximative method in two dimensions. The results obtained are used to categorize the ground-state configurations according to common features (charge and spin ordering) for all f and d electron concentrations ($n_f$ and $n_d$) on finite square lattices. It is shown that only a few configuration types form the basic structure of the charge phase diagram in the $n_f-n_d$ plane. In particular, the largest regions of stability correspond to the phase segregated configurations and configurations that can be considered as mixtures of chessboard configurations and the full (empty) lattice. Since the magnetic phase diagram is much richer than the charge phase diagram, the magnetic superstructures are examined only at selected values of f and d electron concentrations.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 101-103
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamics of the Generalized Spin-One-Half Falicov-Kimball Model in Two Dimensions
Autorzy:
Žonda, M.
Farkašovský, P.
Čenčariková, H.
Powiązania:
https://bibliotekanauki.pl/articles/1810315.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Lp
71.27.+a
71.28.+d
Opis:
The extrapolation of small-cluster exact-diagonalization calculations and the Monte Carlo method is used to study the spin-one-half Falicov-Kimball model extended by the spin-dependent Coulomb interaction (J) between the localized f and itinerant d electrons as well as the on-site Coulomb interaction $(U_{ff})$ between the localized f electrons. It is shown that in the symmetric case the ground-state phase diagram of the model has an extremely simple structure that consists of only two phases, and namely, the charge-density-wave phase and the spin-density-wave phase. The nonzero temperature studies showed that these phases persist also at finite temperatures. The same calculations that we performed for unsymmetric case showed that charge and spin ordering can be destroyed simultaneously or consecutively.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 104-106
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
X-Ray Resonant Magnetic Scattering: Application to Thin Films and Multilayers
Autorzy:
Raoux, D.
Jaouen, N.
Tonnerre, J. M.
Bontempi, E.
Powiązania:
https://bibliotekanauki.pl/articles/2014370.pdf
Data publikacji:
2000-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
78.70.Ck
71.27.+a
Opis:
This paper reports on the use of a new technique to investigate the magnetic properties of thin films, multilayers and artificial structures, the X-ray resonant magnetic scattering at small values of the scattering vector. It can be used either by registering the reflectivity pattern or in a diffraction mode. In comparison with magneto-optical Kerr effect or neutron scattering, it offers an atomic selectivity due to the resonant excitation of a core electron, and even an electronic shell one. Examples are presented mainly in the soft X-range allowing to probe the 3d band of transition metals. They demonstrate the promising possibilities of the method to measure the magnetic moments carried by each of the atomic components in complex systems, as well as their distribution through thin layers, with an atomic resolution.
Źródło:
Acta Physica Polonica A; 2000, 98, 5; 483-494
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 45

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