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Tytuł:
Pressure Induced Transitions in Heavy-Fermion Systems footnotemark
Autorzy:
Zhang, Sun
Dong, Yi-Qiao
Powiązania:
https://bibliotekanauki.pl/articles/1401900.pdf
Data publikacji:
2015-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Mb
75.20.Hr
71.28.+d
74.62.Fj
Opis:
In this paper, the electron-type heavy-fermion system and the hole-type heavy-fermion system are classified by means of the cell-volume difference between two typical valence states of f ions. Two kinds of transitions induced by pressure are studied theoretically within a unified picture presented for both two types of heavy-fermion systems. Among these transitions, the incoherence-to-coherence transition in the electron-type heavy-fermion system is confirmed intensively in experiments, while the coherence-to-incoherence transition in the hole-type heavy-fermion system is discussed as a prediction for further observations.
Źródło:
Acta Physica Polonica A; 2015, 128, 3; 389-393
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anisotropy of Magnetic Interactions in HgFeSe
Autorzy:
Wilamowski, Z.
Przybylińska, H.
Joss, W.
Guillot, M.
Powiązania:
https://bibliotekanauki.pl/articles/1921599.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ey
75.20.Hr
Opis:
Magnetic properties (susceptibility, high-field torque and magnetization) of cubic HgFeSe are analyzed. Van Vleck magnetism of Fe$\text{}^{2+}$ is well evidenced. The energy splitting of the Fe levels in HgSe is shown to differ considerably from that in other II-VI compounds.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 689-692
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Poor Mans Scaling and Green Function Analysis of the Kondo Anomaly in Single-Level Quantum Dots
Autorzy:
Wawrzyniak, M.
Świrkowicz, R.
Wilczyński, M.
Barnaś, J.
Powiązania:
https://bibliotekanauki.pl/articles/1813883.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Hr
72.15.Qm
72.25.-b
73.23.Hk
Opis:
Kondo effect in a single-level quantum dot attached to magnetic leads is studied theoretically by the "poor man's scaling" and non-equilibrium Green function methods. From the scaling equations we derive the Kondo temperature as a function of the model parameters - in particular as a function of the angle between magnetic moments. Transport characteristics, i.e. differential conductance and tunnel magnetoresistance associated with magnetization rotation, were calculated within the non-equilibrium Green function formalism based on the equation of motion method.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 553-556
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Poor Mans Scaling Approach to the Kondo Effect in a Single Quantum Dot Asymmetrically Attached to Ferromagnetic Leads with Non-Collinear Magnetizations
Autorzy:
Wawrzyniak, M.
Powiązania:
https://bibliotekanauki.pl/articles/1812020.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Hr
72.15.Qm
72.25.-b
73.23.Hk
Opis:
The poor man's scaling technique is applied to the problem of electronic transport through a single quantum dot (with finite Coulomb repulsion) asymmetrically coupled to electrodes. The considered quantum dot is coupled to ferromagnetic electrodes, whose magnetic moments are non-collinear. The analysis and numerical illustration of spin splitting of the dot level as well as of the Kondo temperature on the coupling asymmetry is presented and discussed.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1421-1424
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cr-Based II-VI Semimagnetic Semiconductors
Autorzy:
Twardowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1931875.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Dg
75.30.Gw
75.50.Pp
75.20.Hr
78.30.Fs
Opis:
We review the magnetic and optical properties of recently grown Cr-based II-VI semimagnetic semiconductors. We focus on two features of these materials which distinguish them from other semimagnetic semiconductors: the particular magnetic behaviour of these crystals, resulting from the Cr$\text{}^{++}$ ion energy structure determined by a strong, static Jahn-Teller effect, and a ferromagnetic p-d exchange interaction, which is unique for II-VI semimagnetic semiconductors.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 85-93
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anomalous Transport and Thermal Properties of the Solid Solutions U$\text{}_{1-x}$Th$\text{}_{x}$Cu$\text{}_{5}$M (M = Al, Ga, In and Sn)
Autorzy:
Troć, R.
Tran, V. H.
Kaczorowski, D.
Czopnik, A.
Powiązania:
https://bibliotekanauki.pl/articles/2011211.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Mb
72.15.Qm
75.20.Hr
Opis:
UCu$\text{}_{5}$M-type compounds are moderate heavy fermion systems with an antiferromagnetic order below T$\text{}_{N}$ = 18, 16-25, and 25 K for M = Al, (Ga, In), and In, respectively, and a ferrimagnetic order with T$\text{}_{C}$ = 54 K for M = Sn. We present the results of magnetoresistance measurements as a function of temperature and applied magnetic field for the pure compounds and for their solid solutions containing Th, i.e. U$\text{}_{1-x}$Th$\text{}_{x}$Cu$\text{}_{5}$M. Only in the case of UCu$\text{}_{5}$In a substantial positive contribution to the magnetoresistance was observed at low temperatures, as for normal antiferromagnets. For the Al- and Sn-based alloys the magnetoresistance at low temperatures is negative, and its field variation proves the existence of Kondo-type interactions. On Th-substitution the magnetic phase transition is shifted to lower temperature and simultaneously the magnetoresistance becomes less negative. The field dependence of the magnetoresistance of these alloys can be well described by the Coqblin-Schrieffer model. Interestingly, the heat capacity measurements have revealed a general tendency to increase the linear coefficient γ with magnetic dilution of a given UCu$\text{}_{5}$M compound by Th-substitution. This feature reflects an enlargement of the effective mass of conduction electrons with the increase in both the unit cell volume and magnetic dilution. Such a tendency is also observed for the system UCu$\text{}_{5}$(In$\text{}_{1-x}$Ga$\text{}_{x}$), though the unit cell is here suppressed with increasing x. Thus, a similar physical picture is reached in all these systems but involving probably different mechanisms.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 25-35
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
X-Ray Magnetic Circular Dichroism Studies on $CeNi_4B$
Autorzy:
Toliński, T.
Cezar, J.
Wende, H.
Kowalczyk, A.
Baberschke, K.
Powiązania:
https://bibliotekanauki.pl/articles/1810402.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Lp
75.20.Hr
78.70.Dm
79.60.-i
78.20.Ls
Opis:
The $CeNi_4B$ compound is a mixed-valence system. It is a paramagnet with $μ_\text{eff}$= 0.52 $μ_{B}$/f.u. and the paramagnetic Curie temperature θ= -10.7 K. In the present research we complete our previous magnetic susceptibility and X-ray photoemission measurements with new studies by the X-ray magnetic circular dichroism method. The observation of the Ce $M_{4,5}$ edges carried out with X-ray magnetic circular dichroism confirms the mixed-valence state deduced previously from X-ray photoemission spectroscopy. Moreover, we report on the measurements of the Ni $L_{2,3}$ edges, which enable verification of the Ni contribution to the magnetism of this compound.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 129-131
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Electronic Structure of the RMn$\text{}_{2}$Ge$\text{}_{2}$ (R = Ca, Y, La, Ba) Antiferromagnets
Autorzy:
Toboła, J.
Malaman, B.
Venturini, G.
Powiązania:
https://bibliotekanauki.pl/articles/2013367.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
71.15.Nc
75.20.En
75.20.Hr
75.50.Ee
Opis:
The electronic structure of the tetragonal RMn$\text{}_{2}$Ge$\text{}_{2}$ (R = Ca, Y, La, Ba) antiferromagnets is presented using the self-consistent Korringa-Kohn-Rostoker method. According to the neutron refinements, two types of collinear antiferromagnetic structure are taken into account: AF$\text{}_{1}$ for YMn$\text{}_{2}$Ge$\text{}_{2}$ and AF$\text{}_{2}$ for the other compounds. The calculated magnetic moments on Mn: 2.17μ$\text{}_{B}$ (YMn$\text{}_{2}$Ge$\text{}_{2}$), 2.84 μ$\text{}_{B}$ (CaMn$\text{}_{2}$Ge$\text{}_{2}$), 2.95 μ$\text{}_{B}$ (LaMn$\text{}_{2}$Ge$\text{}_{2}$), and 3.47 μ$\text{}_{B}$ (BaMn$\text{}_{2}$Ge$\text{}_{2}$) remain in good agreement with the neutron data (in μ$\text{}_{B}$) 2.20, 2.67, 3.05, and 3.66, respectively. As seen on antiferromagnetic density of states, all systems are metallic, however BaMn$\text{}_{2}$Ge$\text{}_{2}$ is found near semimetallic limit. The total energy Korringa-Kohn-Rostoker computations on CaMn$\text{}_{2}$Ge$\text{}_{2}$, performed in both antiferromagnetic phases, result in preferring of the AF $\text{}_{2}$ structure.zap
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 761-765
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties and Electronic Structure of CeTIn (T = Ni, Cu, Pd, Au) Compounds
Autorzy:
Szytuła, A.
Penc, B.
Gondek, Ł.
Powiązania:
https://bibliotekanauki.pl/articles/2047306.pdf
Data publikacji:
2007-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Eh
71.27.+a
75.20.Hr
79.60.-i
Opis:
The electronic structure of the ternary CeTIn (T = Ni, Cu, Pd, Au) compounds was investigated by means of X-ray photoelectron spectroscopy. Our interest was aimed mainly to the valence bands and the Ce3d core levels of investigated compounds. Analysis of the valence bands indicates that they are mainly determined by the Tnd band, whereas a share of the R4f states can be estimated to be about a few percent only. The analysis of the differential valence bands spectra between CeTIn and LaTIn analogues suggests that the Ce4f$\text{}^{1}$ ground states shift deeper below the Fermi level with an increase in the 4f level occupation factor. The analysis of the Ce3d spectra made on the basis of the Gunnarsson-Schönhammer model indicates the hybridization parameter equal to 148 meV for CeNiIn, 45 meV for CeCuIn, 177 meV for CePdIn, and 123 meV for CeAuIn.
Źródło:
Acta Physica Polonica A; 2007, 111, 4; 475-486
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mixed-Valence State in $Yb_2CuGe_6$
Autorzy:
Szytuła, A.
Penc, B.
Konyk, M.
Winiarski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1813177.pdf
Data publikacji:
2008-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Lp
75.20.Hr
79.60.-i
Opis:
We present here temperature dependent X-ray photoemission measurements on polycrystalline $Yb_2CuGe_6$. The analysis of these data shows the change in the effective valence, determined directly from the 4f intensity ratio, as a function of temperature.
Źródło:
Acta Physica Polonica A; 2008, 113, 4; 1205-1209
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Polarized Transport through the Double-Dot System
Autorzy:
Sztenkiel, D.
Świrkowicz, R.
Powiązania:
https://bibliotekanauki.pl/articles/2044544.pdf
Data publikacji:
2005-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Hr
72.15.Qm
72.25.-b
73.23.Hk
Opis:
Spin-dependent electron transport through two quantum dots in series attached to ferromagnetic electrodes is analyzed within the framework of the non-equilibrium Green function formalism. Regime of a weak coupling between the dots is investigated. I-V characteristics and tunnel magnetoresistance are calculated and discussed in detail.
Źródło:
Acta Physica Polonica A; 2005, 108, 5; 885-890
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic and Magnetic Properties of $ThCo_4B$
Autorzy:
Szajek, A.
Powiązania:
https://bibliotekanauki.pl/articles/1813651.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
75.20.Hr
Opis:
$ThCo_4B$ compound crystallizes in the hexagonal $CeCo_4B$ type structure. The electronic structure is calculated based on full-potential local-orbital full-relativistic method. The ab initio calculations showed that small magnetic moments (≈0.1 $μ_B$/atom) are formed on Th and B atoms, antiparallel to the moments on Co atoms equal to 1.55 and 0.43 $μ_B$/atom for Co(2c) and Co(6i), respectively. The densities of states at the Fermi level are equal to 1.3 and 5.4 states/(eV spin f.u.) for spin up and down, respectively. These values are predominated by Co(3d) electrons.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 283-286
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Transport through the Double-Dot System
Autorzy:
Świrkowicz, R.
Sztenkiel, D.
Powiązania:
https://bibliotekanauki.pl/articles/2038086.pdf
Data publikacji:
2004-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Hr
72.15.Qm
72.25.-b
73.23.Hk
Opis:
Electron tunnelling through two quantum dots in series is theoretically studied. A limit of intermediate coupling between the dots is considered. The non-equilibrium Green function formalism is used to calculate electric current and mean number of electrons accumulated on the dots. Lesser and retarded Green functions are calculated in the Hartree-Fock approximation with the use of the equation of motion method. Current flowing through the system calculated in dependency on gate voltages shows two resonant peaks, each peak with two additional shoulders. I-V characteristics and differential conductance in a resonance and out of resonance cases are calculated and discussed.
Źródło:
Acta Physica Polonica A; 2004, 105, 6; 523-528
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonequilibrium Kondo Effect in a Single-Channel Quantum Dot Asymmetrically Coupled to Two Ferromagnetic Reservoirs
Autorzy:
Świrkowicz, R.
Wilczyński, M.
Barnaś, J.
Powiązania:
https://bibliotekanauki.pl/articles/2037118.pdf
Data publikacji:
2004
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Hr
72.15.Qm
72.25.-b
73.23.Hk
Opis:
Nonequilibrium Kondo effect in a quantum dot asymmetrically coupled to two ferromagnetic metallic leads is analyzed theoretically. The nonequilibrium Green function technique is used to calculate density of states and electric current. The lesser and retarded (advanced) Green functions are calculated by the equation of motion method within a consistent approximation scheme. The case where one electrode is half-metallic is analyzed numerically in details.
Źródło:
Acta Physica Polonica A; 2004, 105, 1-2; 149-154
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Coqblin-Schrieffer Impurity with Local Exchange Coupling: a Perturbative Approach
Autorzy:
Stefański, P.
Powiązania:
https://bibliotekanauki.pl/articles/2013008.pdf
Data publikacji:
2000-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Hf
71.20.Eh
72.15.Qm
75.20.Hr
Opis:
The Coqblin-Schrieffer one-impurity model with the additional local exchange interaction is studied within diagrammatic approach. The Ruderman-Kittel-Kasuya-Yoshida-type local exchange interaction between f electrons of the impurity and a channel of conduction electron l=0 partial waves is treated in the molecular field approximation. The perturbation expansion resummation for the Coqblin-Schrieffer hybridization mediated interaction vertex part is carried out in the ladder approximation yielding the formula for the Kondo temperature T$\text{}_{K}$ decreasing with increased local exchange. Moreover, the temperature divergence of the susceptibility at T$\text{}_{K}$ is shifted towards T=0. For some critical strength of the local exchange interaction the susceptibility approaches a Curie-type dependence as for an uncompensated impurity magnetic moment. A relation to the "Kondo disorder" model, which leads to the non-Fermi-liquid behavior, is discussed.
Źródło:
Acta Physica Polonica A; 2000, 97, 3; 385-388
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 51

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