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Tytuł:
Ab Initio Study of Electronic and Magnetic Structure and Structural Phase Transition of $(Fe_{1 - x}Mn_{x})_2P_{1 - y}Ge_{y}$ Alloys
Autorzy:
Deniszczyk, J.
Woźniakowski, A.
Kolano, R.
Kolano-Burian, A.
Powiązania:
https://bibliotekanauki.pl/articles/1427520.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Be
75.20.Hr
Opis:
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.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1162-1164
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:
Anisotropy of Susceptibility and Optical investigation of the Antiferromagnetic phase Transition in U$\text{}_{1-x}$Ce$\text{}_{x}$Ru$\text{}_{2}$Si$\text{}_{2}$
Autorzy:
Mihalik, M.
Maťaš, S.
Macko, D.
Timko, M.
Menovsky, A. A.
Powiązania:
https://bibliotekanauki.pl/articles/1955512.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Hb
75.20.Hr
72.15.-v
Opis:
Temperature dependence of magnetic susceptibility of U$\text{}_{1-x}$Ce$\text{}_{x}$Ru $\text{}_{2}$Si$\text{}_{2}$ single crystals (x=0, 0.025, 0.05, 0.075) has been studied at temperatures from 4.2 K up to room temperature and in magnetic fields applied along and perpendicular to the c-axis. The attention was paid to anomalies connected with the antiferromagnetic phase transition, which are present in crystals with x≤0.05. Far-infrared measurements of U$\text{}_{0.99}$Ce$\text{}_{0.01}$ Ru$\text{}_{2}$Si$\text{}_{2}$ single crystal have been studied for the first time. The measurements support the assumption that the origin of magnetic ordering in U$\text{}_{0.99}$Ce$\text{}_{0.01}$Ru$\text{}_{2}$Si$\text{}_{2}$ is the same as in heavy-fermion superconductor URu$\text{}_{2}$Si$\text{}_{2}$ and can be interpreted as being due to a spin-density-wave gap.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 351-354
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:
Aspects of Magnetism in Heavy-Electron Metals
Autorzy:
Ott, H. R.
Powiązania:
https://bibliotekanauki.pl/articles/1860764.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.-g
75.20.Hr
75.30.-m
75.30.Mb
Opis:
For some time it was believed that heavy-mass electrons at low temperatures, in special rare-earth and actinide compounds, were due to a particular suppression of magnetic order in these materials. Various experiments reveal, however, that magnetic order may occur from a heavy-electron state and that also a heavy-electron state may develop in the presence of a magnetically-ordered matrix. Even in materials with no sign of a cooperative phase transition, microscopic experimental probes give evidence for strong magnetic correlations, involving only very tiny (< 10^{-1} μ_{B}) ordered moments, however. All these experimental observations indicate that the heavy-electron state cannot always be regarded as a simple Fermi liquid in the usual sense. Various interactions of similar strength need to be considered. It is suggested that the balance of these interactions may lead to electronic inhomogeneities in k space. Both in magnetically-ordered or superconducting systems, unexpected electronic degrees of freedom appear to exist. In other cases experimental observations suggest magnetic inhomogeneities in real space which are not simply due to chemical inhomogeneities. Different examples of these various possibilities are demonstrated and discussed.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 7-19
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
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:
Dynamic Crystal Field in CePb$\text{}_{3}$
Autorzy:
Lipiński, S.
Szajek, A.
Powiązania:
https://bibliotekanauki.pl/articles/2012928.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Dg
75.20.Hr
75.30.Mb
Opis:
The crystal field of valence fluctuating systems is time dependent due to f-electron transfers to the conduction band. We examine the effects of crystal field fluctuations on the neutron spectra, the specific heat and susceptibility of CePb$\text{}_{3}$.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 245-248
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Co substitution on Ni₂MnGe Heusler alloy: ab initio study
Autorzy:
Pugaczowa-Michalska, M.
Powiązania:
https://bibliotekanauki.pl/articles/1048335.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Hr
71.23.-k
75.70.Ak
75.70.Cn
Opis:
Ab initio calculations shown that the Co substitution instead of Ni in Ni₂MnGe with the L2₁ crystallographic structure leads to a decrease of the lattice constant and an increase of the total magnetic moment of the Ni_{2-x}Co_{x}MnGe compounds. The Mn(B) has the largest local moment above 3 μ_{B} coupled parallel to moments on the Ni(A,C) and Co(A,C), which are found in the ranges of 0.19÷0.26 μ_{B} for Ni(A,C) and 1.03÷0.97 μ_{B} for Co(A,C) for studied range of x. Using the results stemming from the total energy calculations, the values of bulk modulus and its pressure derivatives are estimated according to the Murnaghan EOS.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 495-497
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 Structure and Magnetic Properties of $La_{1-x}Ce_{x}Pb_3$ and $La_{1-x}Pr_{x}Pb_3$ Alloys
Autorzy:
Jezierski, A.
Kaczkowski, J.
Cichorek, T.
Powiązania:
https://bibliotekanauki.pl/articles/1207412.pdf
Data publikacji:
2014-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
71.20.Eh
71.20.Gj
75.20.Hr
Opis:
The electronic structure and magnetic properties of $La_{1-x}Ce_{x}Pb_3$ and $La_{1-x}Pr_{x}Pb_3$ are studied using the spin-polarized relativistic Korringa-Kohn-Rostoker coherent potential approximation method within the local spin density approximation. The calculated density of states at the Fermi level increases with the increase of the concentration. The dependence of spin and orbital magnetic moments of $La_{1-x}Ce_{x}Pb_3$ and $La_{1-x}Pr_{x}Pb_3$ (0 < x < 1) on the concentration is also reported. The densities of states at the Fermi energy are dominated by Ce(Pr) $4f_{5/2}$ and $4f_{7/2}$ states.
Źródło:
Acta Physica Polonica A; 2014, 125, 1; 111-114
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:
Ferromagnetism and Metal-Insulator Transitions in Correlated Electron Systems with Alloy Disorder
Autorzy:
Byczuk, K.
Yu, U.
Hofstetter, W.
Vollhardt, D.
Powiązania:
https://bibliotekanauki.pl/articles/1810278.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.23.-k
75.20.Hr
75.30.Mb
Opis:
Alloy disorder can affect ferromagnetism and metal-insulator transitions of correlated lattice fermion systems in subtle and often unexpected ways. Solving the Hubbard model and the periodic Anderson model within dynamical mean-field theory we show that alloy disorder can increase the Curie temperature of a non-disordered system, and also yields novel Mott or Kondo insulators at fractional electronic densities.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 7-12
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Importance of the Spin-Orbit Coupling for 3d-Ion Compounds: the Case of NiO
Autorzy:
Radwański, R. J.
Ropka, Z.
Powiązania:
https://bibliotekanauki.pl/articles/2013984.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Hr
71.70.Ej
Opis:
The orbital and spin moment of the Ni$\text{}^{2+}$ ion in NiO has been calculated at 0 K to be 0.54 μ$\text{}_{B}$ and 1.99 μ$\text{}_{B}$ respectively. Such large orbital moment, more than 20% of the total moment of 2.53 μ$\text{}_{B}$, proves the need for the "unquenching" of the orbital moment in compounds containing 3d ions. It turns out that the spin-orbit coupling is indispensable for description of magnetic and electronic properties of 3d-ion compounds.
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 963-965
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Bound Magnetic Polarons on Magnetic and Electrical Properties in Metallic n-Cd$\text{}_{0.95}$Mn$\text{}_{0.05}$Se
Autorzy:
Głód, P.
Sawicki, M.
Dietl, T.
Skośkiewicz, T.
Lenard, A.
Plesiewicz, W.
Powiązania:
https://bibliotekanauki.pl/articles/1931936.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.38.+i
75.20.Hr
Opis:
Doping-induced contribution to the millikelvin magnetic susceptibility of Cd$\text{}_{0.95}$Mn$\text{}_{0.05}$Se:In has been found to undergo a maximum at n ≈ 2n$\text{}_{c}$, and to vanish for n ≥ 8n$\text{}_{c}$, where n$\text{}_{c}$ is the electron concentration corresponding to the metal-insulator transition. This confirms the presence, also in the metallic phase, of bound magnetic polarons. Their slow dynamics may account for hysteresis visible in our magnetoresistance data.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 173-175
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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