Temat: 75.10.Pq - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Spin-1/2 XXZ Diamond Chain within the Jordan-Wigner Fermionization Approach
Autorzy:: Verkholyak, T.
Strečka, J.
Jaščur, M.
Richter, J.
Powiązania:: https://bibliotekanauki.pl/articles/1535012.pdf
Data publikacji:: 2010-11
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 75.10.Jm
75.10.Pq
Opis:: The spin-1/2 XXZ diamond chain is considered within the Jordan-Wigner fermionization. The fermionized Hamiltonian contains the interacting terms which are treated within the Hartree-Fock approximation. We obtain the ground-state magnetization curve of the model for some particular cases and compare the results with the exact diagonalization data for finite chains of 30 spins and known exact results. We also analyze the validity of the suggested approximation.
Źródło:: Acta Physica Polonica A; 2010, 118, 5; 978-979
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Magnetic Exchange Interactions and Estimation of $T_N$ in $CsNiF_3$ from First Principles
Autorzy:: Legut, D.
Rusz, J.
Powiązania:: https://bibliotekanauki.pl/articles/1813855.pdf
Data publikacji:: 2008-01
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 75.10.Pq
75.30.Et
Opis:: The $CsNiF_3$ has been for long time studied as a prototype of quasi-1D planar ferromagnetic system. At very low temperature the studied system is insulator and therefore the magnetic exchange interactions should decay very rapidly. We treated the magnetic exchange coupling within the Heisenberg model for the nearest neighbor interaction between the anti-ferromagnetically coupled Ni-chains. The influence of up to the second-nearest neighbors on the ferromagnetic exchange coupling along the Ni-chains was determined. The exchange interactions were calculated for the experimental volume by the density functional theory, within the all-electron approach using the local density approximation for the exchange and correlation. The Néel temperature was calculated by means of the mean-field theory and by the random-phase approximation method.
Źródło:: Acta Physica Polonica A; 2008, 113, 1; 503-506
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Thermodynamics of the Exactly Solvable Spin-Electron Tetrahedral Chain
Autorzy:: Gálisová, L.
Powiązania:: https://bibliotekanauki.pl/articles/1402558.pdf
Data publikacji:: 2015-08
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 05.70.-a
75.10.Pq
Opis:: An exactly solvable spin-electron tetrahedral chain, where the Ising spins localized at nodal lattice sites regularly alternate with three equivalent lattice sites available for one mobile electron is considered. The system with ferromagnetic interaction between the Ising spins and electrons exhibits an enhanced magnetocaloric effect in the limit H/|J| → 0 when the entropy is very small, whereas the system with antiferromagnetic interaction between the Ising spins and electrons exhibits an enhanced magnetocaloric effect around the field H/J=1 when the entropy is sufficiently close to the value S/2N = ln[(1+√5)/2]. We study the thermodynamics of the system in these field regions.
Źródło:: Acta Physica Polonica A; 2015, 128, 2; 156-158
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: On Theoretical Study of Magnetic Behavior of Diamond Doped with Transition Metals
Autorzy:: Hussain, F.
Ullah, M.
Ullah, H.
Rashid, M.
Imran, M.
Ahmad, E.
Powiązania:: https://bibliotekanauki.pl/articles/1399279.pdf
Data publikacji:: 2015-03
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 75.10.Kt
75.10.Pq
75.30.Hx
Opis:: We study the magnetic behavior of the diamond system. In this system diamond bulk is involved which is doped with different transition metals, namely Cu, Cd, Hg, and Zn. The VASP code is employed for all calculations which are based on density functional theory. The substitutional point defects is introduced in the diamond bulk and occupied by the transition metals. Results exhibit that all transition metals show ferromagnetism behavior and Cu is a good advocate of conductivity among all transition metals. The range of magnetic moments is 2.89, 1.99, 1.96, and 1.80 $μ_{B}$ per Cu, Cd, Hg, and Zn atom in diamond bulk, respectively. Strong magnetic behavior points out that these materials could be used for spintronics.
Źródło:: Acta Physica Polonica A; 2015, 127, 3; 823-826
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Spin Chain in Magnetic Field: Limitations of the Large-N Mean-Field Theory
Autorzy:: Wohlfeld, K.
Chen, Cheng-Chien
van Veenendaal, M.
Devereaux, T.
Powiązania:: https://bibliotekanauki.pl/articles/1384813.pdf
Data publikacji:: 2015-02
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 71.10.Fd
75.10.Jm
75.10.Pq
Opis:: Motivated by the recent success in describing the spin and orbital spectrum of a spin-orbital chain using a large-N mean-field approximation, we apply the same formalism to the case of a spin chain in the external magnetic field. It occurs that in this case, which corresponds to N=2 in the approximation, the large-N mean-field theory cannot qualitatively reproduce the spin excitation spectra at high magnetic fields, which polarize more than 50% of the spins in the magnetic ground state. This, rather counterintuitively, shows that the physics of a spin chain can under some circumstances be regarded as more complex than the physics of a spin-orbital chain.
Źródło:: Acta Physica Polonica A; 2015, 127, 2; 201-203
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: $Cu_3(tmen)_3(tma)_2(H_2O)_2$ · $6.5H_2O$ - New S = 1/2 "Sawtooth" Chain?
Autorzy:: Vrábel, P.
Orendáčová, A.
Černák, J.
Orendáč, M.
Powiązania:: https://bibliotekanauki.pl/articles/1535093.pdf
Data publikacji:: 2010-11
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 75.10.Jm
75.10.Pq
75.30.Et
Opis:: The results of the investigation of magnetic susceptibility, magnetization and specific heat of $Cu_3(tmen)_3(tma)_2(H_2O)_2$ · $6.5H_2O$ (tmen = N,N,N',N'-tetramethylethane-1,2 diamine; $H_3$ tma = 1,3,5-benzenetricarboxylic acid) are reported. The spatial arrangement of magnetic Cu(II) ions and network of covalent bonds suggest that the studied material might be a representative of S = 1/2 sawtooth chain with moderate exchange coupling J/$k_{B}$. The investigation of the temperature dependence of susceptibility and magnetic field dependence of magnetization yielding J/$k_{B}$ ≈ - 0.63 K is consistent with the structural features. In addition, specific heat data reveal short-range correlations in milikelvin temperature range and indicate long-range ordering below 150 mK.
Źródło:: Acta Physica Polonica A; 2010, 118, 5; 993-994
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Kinetically-Driven Frustration in Hybrid Spin Ladders
Autorzy:: Carvalho, R.
Pereira, M.
Lyra, M.
Rojas, O.
Strecka, J
Powiązania:: https://bibliotekanauki.pl/articles/1199484.pdf
Data publikacji:: 2014-07
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 75.10.Jm
75.10.Pq
05.70.Ce
Opis:: We introduce a spin ladder model incorporating localized and delocalized spins, which is exactly solvable using the decoration-iteration and transfer-matrix techniques. Quantum correlations between delocalized spins induce an antiferromagnetic coupling between the spin chains that competes with a direct ferromagnetic exchange coupling. A resulting kinetically-driven frustration is predominant in the regime of low temperatures and large hopping amplitudes. We provide the full ground-state phase diagram, as well as the frustration diagram on distinct coupling regimes.
Źródło:: Acta Physica Polonica A; 2014, 126, 1; 12-13
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Polaron States in a CuO Chain
Autorzy:: Bieniasz, K.
Oleś, A.
Powiązania:: https://bibliotekanauki.pl/articles/1385209.pdf
Data publikacji:: 2015-02
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 72.10.Di
75.10.Pq
75.50.Ee
Opis:: We introduce a one-dimensional model for a CuO chain, with holes and S=1/2 spins localized in $3d_{x²-y²}$ orbitals, and p_σ oxygen orbitals without holes in the ground state. We consider a single hole doped at an oxygen site and study its propagation by spin-flip processes. We develop the Green function method and treat the hole-spin coupling in the self-consistent Born approximation, similar to that successfully used to study polarons in the regular t-J model. We present an analytical solution of the problem and investigate whether the numerical integration is a good approximation to this solution.
Źródło:: Acta Physica Polonica A; 2015, 127, 2; 269-271
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Comparison of the Multi-Band Hubbard and Heisenberg Models on Small Finite Clusters
Autorzy:: Matysiak, J.
Lemański, R.
Powiązania:: https://bibliotekanauki.pl/articles/1030762.pdf
Data publikacji:: 2018-03
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 31.15.vq
75.10.Jm
75.10.Pq
Opis:: We perform exact numeric calculations for a few versions of the two-orbital Hubbard model on the four site cluster. We show that the conventional spin 1 Heisenberg Hamiltonian can be obtained in the strong coupling limit, but only for some versions of the two-orbital Hubbard model. Then we propose a modified version of the Heisenberg Hamiltonian, that we call the two-orbital Heisenberg model, which is relevant in those cases, where the conventional spin 1 Heisenberg model fails.
Źródło:: Acta Physica Polonica A; 2018, 133, 3; 405-407
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Magnetocaloric Effect in NiCl₂(bipy) at Low Temperatures
Autorzy:: Ráczová, K.
Čižmár, E.
Feher, A.
Powiązania:: https://bibliotekanauki.pl/articles/1032298.pdf
Data publikacji:: 2017-04
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:: 75.30.Sg
75.30.Gw
75.10.Pq
Opis:: Magnetothermal properties of the compound NiCl₂(bipy), where bipy = 4,4'-bipyridine, were studied. The single-ion anisotropy of Ni(II) ions was estimated and its influence on magnetocaloric effect in NiCl₂(bipy) was investigated. Above the metamagnetic transition a maximum in the isothermal change of the magnetic entropy is reached near 11 K at field change from 0T to 7T with peak value -ΔS = 6J K¯¹ kg¯¹. The temperature dependence of ΔS above 7K agrees with the assumed easy-axis type of single-ion anisotropy. The inverse magnetocaloric effect, typical for ordered antiferromagnets, was observed in the ordered state of NiCl₂(bipy) only for isothermal magnetization in small fields up to 2T.
Źródło:: Acta Physica Polonica A; 2017, 131, 4; 922-924
0587-4246
1898-794X
Pojawia się w:: Acta Physica Polonica A
Dostawca treści:: Biblioteka Nauki

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