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Wyświetlanie 1-15 z 15
Tytuł:
The Competing Interactions on a Cayley Tree-Like Lattice: Pentagonal Chandelier
Autorzy:
Uguz, S.
Ganikhodjaev, N.
Akin, H.
Temir, S.
Powiązania:
https://bibliotekanauki.pl/articles/1490904.pdf
Data publikacji:
2012-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.50.+q
64.60.-i
64.60.De
Opis:
Different types of lattice spin systems with competing interactions have rich and interesting phase diagrams. In this study we present some new results for such systems involving the Ising spin system (i.e. σ = ± 1) using a generalization of the Cayley tree-like lattice approximation. We study the phase diagrams for the Ising model on a Cayley tree-like lattice, a new lattice type called pentagonal chandelier, with competing nearest-neighbor interactions $J_1$, prolonged next-nearest-neighbor interactions $J_{p}$ and one-level next-nearest-neighbor senary interactions $J_{l_1}^{(6)}$. The colored phase diagrams contain some multicritical Lifshitz points that are at nonzero temperature and many modulated new phases. We also investigate the variation of the wave vector with temperature in the modulated phase and the Lyapunov exponent associated with the trajectory of the system.
Źródło:
Acta Physica Polonica A; 2012, 121, 1; 114-118
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Behaviors of Phase Diagrams of Ising Model with Competing Ternary and Binary Interactions on a Cayley Tree of Arbitrary Order
Autorzy:
Akin, H.
Ganikhodjaev, N.
Uguz, S.
Temir, S.
Powiązania:
https://bibliotekanauki.pl/articles/1490877.pdf
Data publikacji:
2012-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.50.+q
64.60.-i
64.60.De
Opis:
An Ising model with competing interactions has recently been studied extensively because of the appearance of nontrivial magnetic orderings. In this paper, we study the phase diagrams for the Ising model on a Cayley tree with competing nearest-neighbor interactions J and ternary prolonged interactions $J_{t_{p}}$ on a Cayley tree of arbitrary order k and compare with the phase diagrams obtained in Uguz et al. and Vannimenus results for the Ising model on a Cayley tree with competing nearest-neighbor interactions J and ternary prolonged interactions $J_{p}$. For some values of k, we obtain phase diagrams of the model. We clarify the role of order k of the Cayley tree. We also plot the variation of the wave vector with temperature.
Źródło:
Acta Physica Polonica A; 2012, 121, 1; 104-107
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Asymmetry Driven Phase Transformations
Autorzy:
Damczyk, J.
Ostasiewicz, K.
Radosiński, Ł.
Radosz, A.
Powiązania:
https://bibliotekanauki.pl/articles/1535592.pdf
Data publikacji:
2010-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.70.-a
64.60.-i
63.70.+h
Opis:
Motivated by the properties of one-dimensional lattice systems with asymmetric on-site potential, one can formulate a hypothesis of an asymmetry driven phase transformation. Characteristic feature of one-dimensional systems exhibiting asymmetry driven phase transformation is a sequence of the two phase conversions. In particular class of such systems with a triple-well potential, phase conversions of one-dimensional systems would evolve into a sequence of two phase transitions in three-dimensional models. We propose here a model of three-dimensional system exhibiting a sequence of two first order asymmetry driven phase transitions.
Źródło:
Acta Physica Polonica A; 2010, 118, 4; 527-530
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Melting of Two-Dimensional Monolayer Films
Autorzy:
Patrykiejew, A.
Zientarski, T.
Binder, K.
Powiązania:
https://bibliotekanauki.pl/articles/1945440.pdf
Data publikacji:
1996-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.65.-i
64.60.-i
Opis:
The melting of two-dimensional films formed on the (100) fcc crystal is studied by Monte Carlo simulation. The results obtained suggest that in systems with only weakly corrugated surface potential, exhibiting the hexagonal close packed solid structure, the melting transition is followed by the Ising-type transition as predicted by the theory of Nelson and Halperin. In the case of highly corrugated surface potential, the film forms registered structure which disorders gradually as the temperature is raised.
Źródło:
Acta Physica Polonica A; 1996, 89, 5-6; 735-742
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Phases and Generalized t-J Models in Doped Mott-Hubbard Insulators
Autorzy:
Oleś, A. M.
Zaanen, J.
Powiązania:
https://bibliotekanauki.pl/articles/1861025.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.72.-h
64.60.-i
64.90.+b
75.40.-s
Opis:
We review some recent results obtained for the dynamics of a single hole and for the ground states at finite hole doping in t-J model. Next, we address the role of orbital degeneracy in doped Mott-Hubbard insulators and show examples of effective strong coupling models which include the orbital degrees of freedom. These new t-J models have interesting phase diagrams, with the new magnetic phases stabilized by a competition between magnetic energy and excitonic excitations. It is argued that the doped holes always bind to the excitons and that the new phases identified on the mean-field level give rise to local distortions of the lattice. We conclude that realistic t-J models derived from the electronic structure of particular compounds may be successfully applied for understanding both the observed magnetic ground states, and the results of photoemission experiments, as we have demonstrated recently for NiO.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 145-163
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stripe Phases in the Hubbard Model
Autorzy:
Góra, D.
Rościszewski, K.
Oleś, A. M.
Powiązania:
https://bibliotekanauki.pl/articles/2012901.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
74.72.-h
75.10.-b
64.60.-i
Opis:
We investigate the magnetic and charge ordering in the stripe phases obtained while using correlated wave functions for finite 8×8 clusters described by the Hubbard model with extended hopping. Nonmagnetic vertical (01) site-centered domain walls and (11) bond-centered stripes are found for the parameters of La$\text{}_{2-x}$Sr$\text{}_{x}$CuO$\text{}_{4}$ and YBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{6+x}$, respectively, at doping δ=1/8. The obtained half-filled domain nonmagnetic walls reproduce the maxima observed in neutron scattering for La$\text{}_{2-x}$Sr$\text{}_{x}$CuO$\text{}_{4}$.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 225-228
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Applications of Density Matrix Renormalization Group to Problems in Magnetism
Autorzy:
Gehring, G. A.
Bursill, R. J.
Xiang, T.
Powiązania:
https://bibliotekanauki.pl/articles/1953163.pdf
Data publikacji:
1997-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
11.10.Gh
Opis:
The application of real space renormalization group methods to quantum lattice models has become a topic of great interest following the development of the density matrix renormalization group by White. This method has been used to find the ground and low-lying excited state energies and wave functions of quantum spin models in which the form of the ground state is not clear, for instance because the interactions are frustrated. It has also been applied to fermion problems where the tendency for localization due to the strong Coulomb repulsion is opposed by the lowering of the kinetic energy which occurs as a result of electron transfer. The approach is particularly suitable for one-, or quasi-one-dimensional problems. The method involves truncating the Hilbert space in a systematic and optimised manner. Results for the ground state energy are thus variational bounds. The results for low-lying energies and correlation functions for one-dimensional systems have unprecedented accuracy and the method has become the method of choice for solving one-dimensional quantum spin problems. We review the method and results obtained for the spin-1 chain with biquadratic exchange as well as the spin-1/2 model with competing nearest and next nearest neighbour exchange will be described. More recently, the density matrix renormalization group has been applied to reformulate the coupling constant renormalization group approach which is appropriate for the study of critical properties. This approach has been applied to the anisotropic spin-1/2 Heisenberg chain. Finally, we discuss recent work which has borne promising applications in two dimensions - the Ising model and the two-dimensional Hubbard model.
Źródło:
Acta Physica Polonica A; 1997, 91, 1; 105-119
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
EPR Study of Monoclinic RbD$\text{}_{2}$PO$\text{}_{4}$ Monocrystal Doped with Cr$\text{}^{5+}$ Ion
Autorzy:
Waplak, S.
Shuvalov, L. A.
Powiązania:
https://bibliotekanauki.pl/articles/1932129.pdf
Data publikacji:
1995-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.-v
64.60.-i
Opis:
Deuterated monoclinic RbD$\text{}_{2}$PO$\text{}_{4}$ (DRDP) doped with chromium Cr$\text{}^{5+}$ is studied by EPR in 90 K to 400 K temperature range. EPR reveals two types of paramagnetic centers: single Cr$\text{}^{5+}$ (S = 1/2) complex and Cr$\text{}^{5+}$-Cr$\text{}^{5+}$ coupled pairs with effective spin S = 1. The EPR line splitting of single Cr$\text{}^{5+}$ complex in DRDP versus temperature agrees with the unit cell multiplication. The splitting of EPR line of pair spectrum appears at T* = 160 K, far below the phase transition temperatures and is due to the anisotropy of the exchange interaction. The clustering effect in the low-dimensional DRDP is suggested.
Źródło:
Acta Physica Polonica A; 1995, 87, 3; 643-648
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Earth Materials at High Pressure and Temperature: Recent Contributions from in situ Synchrotron X-Ray Diffraction
Autorzy:
Redfern, S. A. T.
Powiązania:
https://bibliotekanauki.pl/articles/1963306.pdf
Data publikacji:
1997-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
07.35.+k
91.35.-x
Opis:
The application of synchrotron X-ray powder diffraction to the study of minerals and understanding of the structure and dynamics of the Earth's deep interior is summarised. The salient features of the diamond anvil cell and large-volume multi-anvil cell high-P/T apparatus as used at synchrotron radiation sources are described, and recent developments and applications of these techniques within high-P/T mineralogy are reviewed.
Źródło:
Acta Physica Polonica A; 1997, 91, 4; 659-668
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical Simulations of Linear S=1 Ferro- and Antiferromagnets
Autorzy:
Kamieniarz, G.
Matysiak, R.
Caramico D'Auria, A.
Esposito, F.
Esposito, U.
Powiązania:
https://bibliotekanauki.pl/articles/1964696.pdf
Data publikacji:
1997-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
75.10.Hk
75.40.Mg
Opis:
The finite-temperature static properties of the spin S=1 antiferromagnetic Heisenberg chains are extensively simulated using the quantum transfer matrix method. The zero-field susceptibility and specific heat as well as the field-dependent magnetization data are evaluated to select the microscopic parameters of a number of real quasi-one-dimensional compounds and to verify some theoretical approaches.
Źródło:
Acta Physica Polonica A; 1997, 92, 2; 387-389
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electric and Magnetic Properties of Hydrogels Doped with Cu Ions
Autorzy:
Coşkun, R.
Okutan, M.
Yalçın, O.
Kösemen, A.
Powiązania:
https://bibliotekanauki.pl/articles/1418231.pdf
Data publikacji:
2012-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
52.25.Mq
82.35.-x
42.70.Jk
64.60.-i
76.30.-v
Opis:
The electric and magnetic properties of Cu doped and pure/undoped hydrogels were investigated by impedance spectroscopy and electron spin resonance techniques, respectively. The capacitance and dissipation factor (tan δ) were measured in the frequency range of 100 Hz-10 MHz at room temperature. The Cole-Cole plots for the Cu doped dry and pure dry hydrogels have been used to describe the characteristic change of electrical properties in mentioned temperature interval. The comparison between Cu ions doped and pure/undoped samples is done using the impedance spectroscopy and the electron spin resonance techniques. Electron spin resonance signal for pure, Cu doped wet and Cu doped dry samples are not any power absorption signal, near the symmetric with respect to the resonance field values according to the dry sample and asymmetric for resonance field/base line, respectively.
Źródło:
Acta Physica Polonica A; 2012, 122, 4; 683-687
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Growth Dynamics of Photoinduced Phase Domain in Cyano-Complex Studied by Boundary Sensitive Raman Spectroscopy
Autorzy:
Asahara, A.
Nakajima, M.
Fukaya, R.
Tokoro, H.
Ohkoshi, S.
Suemoto, T.
Powiązania:
https://bibliotekanauki.pl/articles/1490049.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
82.50.Hp
78.30.-j
Opis:
Rubidium manganese hexacyanoferrate exhibits charge transfer phase transition from high temperature phase to low temperature phase at 230 K. This phase transition can also be triggered by light irradiation resonantly inducing charge transfer from $Mn^{2+}$ to $Fe^{3+}$. In the present study, boundary sensitive Raman spectroscopy was performed for $Rb_{0.94}Mn[Fe(CN)_6]_{0.98} \cdot 0.2H_2O$ in both cases of photoinduced and thermal phase transition. Since the frequencies of C ≡ N stretching vibration modes are very sensitive to the valence states of the adjacent metal ions, we can quantify the distribution of not only high and low temperature phase but also boundary configurations from the observed spectra. We obtained the time evolution of the fraction ratios of the valence states from the observed peak areas. In the case of photoinduced situation, the boundary increases up to 15% when high temperature phase diminishes to 55% of the initial fraction. This is quite different from the result in thermal phase transition where the boundary is created only 0.8% at the same high temperature phase fraction value. We conclude that many small domains are preferably created in photoinduced phase transition since the ratio of boundary is large, while large domains grow in thermal phase transition.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 375-384
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Reorientation Studies in Nd$\text{}_{2}$Fe$\text{}_{14-x}$Si$\text{}_{x}$B (0
Autorzy:
Gargula, R.
Pędziwiatr, A.
Bogacz, B.
Wróbel, S.
Bartolomé, J.
Stankiewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/2030427.pdf
Data publikacji:
2002-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Ww
76.80.+y
64.60.-i
Opis:
Nd$\text{}_{2}$Fe$\text{}_{14-x}$Si$\text{}_{x}$B (x=0.25, 0.5, 0.75, 1.0, 1.5, 2.0) intermetallic compounds were investigated by magnetometry, $\text{}^{57}$Fe Mössbauer effect, electric resistivity, and differential scanning calorimetry mainly in the vicinity of the spin reorientation temperature, T$\text{}_{SR}$. The Curie temperature, T$\text{}_{C}$, and T$\text{}_{SR}$ were determined for different compositions and the spin phase diagram was constructed. $\text{}^{57}$Fe Mössbauer spectra showed noticeable changes in the reorientation region. For temperatures above the transition, the spectra were analysed using 6 Zeeman patterns associated with 6 inequivalent crystal sites in Nd$\text{}_{2}$Fe$\text{}_{14}$B according to site occupations (16k$\text{}_{1}$:16k$\text{}_{2}$:8j$\text{}_{1}$:8j$\text{}_{2}$:4c:4e). In the transition region, 12 subspectra had to be incorporated in the analysis. Electric resistivity measurements showed a typical metallic behaviour with no anomalies in the magnetic transition region. Differential scanning calorimetry measurements revealed broad endothermic two stage peaks around T$\text{}_{SR}$.
Źródło:
Acta Physica Polonica A; 2002, 101, 2; 289-294
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic Waves Generation in $Ni_{2.14}Mn_{0.81}GaFe_{0.05}$ Heusler Alloy at Structural Phase Transition
Autorzy:
Bychkov, I.
Kuzmin, D.
Kalenov, D.
Kamantsev, A.
Koledov, V.
Kuchin, D.
Shavrov, V.
Powiązania:
https://bibliotekanauki.pl/articles/1387405.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
75.50.Cc
Opis:
Electromagnetic waves generated by the Heusler alloy $Ni_{2.14}Mn_{0.81}GaFe_{0.05}$ at structural phase transition was detected in the frequency range of 28-32 GHz. Influence of the kinetics of phase transitions on the nature of the sample millimeter radiation was studied as well. It has been observed that the contribution of the intrinsic radiation increases with increasing of the heating/cooling rate. The possible mechanisms and theory of such effect is discussed. It is shown that the maximum radiation intensity should be emitted in direction perpendicular to the movement of interphase boundary.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 588-590
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heat Capacity and Elastic Constants of Fe$\text{}_{3-x}$Zn$\text{}_{x}$O$\text{}_{4}$ in the Vicinity of the Verwey Transition
Autorzy:
Kozłowski, A.
Kąkol, Z.
Schwenk, H.
Bareiter, S.
Hinkel, C.
Luthi, B.
Honig, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/2013722.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
63.20.-e
64.60.-i
65.40.+g
Opis:
The results of the heat capacity and elastic constant studies of Fe$\text{}_{3-x}$Zn$\text{}_{x}$O$\text{}_{4}$ (x<0.04) series are reported. Adiabatic heat capacity measurements, performed on single crystals, show the clear change of the transition character from first order for low Zn content (x<0.012) to the higher order in 0.012
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 883-887
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-15 z 15

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