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Tytuł:
Nonclassical Critical Behaviour and Low Temperature Anomalies in Ferroelectric DMACA as Described by Many-Sublattice Model
Autorzy:
Gałązka, M.
Zieliński, P.
Powiązania:
https://bibliotekanauki.pl/articles/1399033.pdf
Data publikacji:
2013-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.10.+h
64.60.-i
64.60.Cn
Opis:
A model based on the crystallographic data on dimethylammonium nonachlorodiantimonate (DMACA) is constructed. Gradual orientational ordering of three inequivalent sublattices of the dimethylammonium cations is shown to be at the origin of the anomalous behaviour of the spontaneous polarisation in this material. A quantitative comparison with the experimental data reveals a temperature dependence of a coupling between two sublattices and a strong deformability of the underlying structure.
Źródło:
Acta Physica Polonica A; 2013, 124, 6; 1013-1019
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:
Embedded Atom Method for Theoretical Strength and Stability of Some fcc Metals
Autorzy:
Öztekin Çiftci, Y.
Çolakoğlu, K.
Powiązania:
https://bibliotekanauki.pl/articles/2028900.pdf
Data publikacji:
2001-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
62.20.-x
Opis:
The structural phase transformation and theoretical strength of fcc metals Ni, Cu, Ag, Al, Au, and Pt under [100] uniaxial loading are studied by using analytical embedded-atom-potential method. In the present calculations the stress-free bcc phase is found unstable and fcc phase is found to be stable. The obtained energy differences of fcc-bcc phases are comparable with those found by the first-principles calculations and experiments for all metals considered. The present pair potential in the embedded-atom method is used for the first time for this purpose. Theoretical lattice parameters, volumes, and energies of the bcc and fcc structures for each metal at zero pressure are calculated and compared with the available experimental values. Third-order elastic constants and pressure-volume curves for studied metals are also investigated and found generally good agreement with experiments.
Źródło:
Acta Physica Polonica A; 2001, 100, 4; 539-551
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:
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:
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:
Temperature and Pressure Dependence of the Linewidth for an Internal Mode in the Solid Phases of Benzene
Autorzy:
Yurtseven, H.
Şenol, M.
Powiązania:
https://bibliotekanauki.pl/articles/1399290.pdf
Data publikacji:
2013-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
05.70.Fh
Opis:
The pressure dependence of the Raman linewidths for the $ν_1$ breathing mode is analyzed using the experimental data from the literature for the solid phases (I, II, III and III') in benzene. Increase (I, III and III') and decrease (II) in the Raman linewidths are described by a power-law analysis with the critical exponent β. The β values we find, which characterize the phase transition are in favour of the first order among those phases considered in benzene. The temperature and pressure dependence of the frequencies and linewidths of various Raman modes can be analyzed using a power-law formula, as studied here for the solid phases (I, II, III and III') in benzene when the experimental data are available in the literature.
Źródło:
Acta Physica Polonica A; 2013, 124, 4; 698-701
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Transition in Quasi-Two-Dimensional Horizontally Driven Granular System
Autorzy:
Shah, S.
Li, Y.
Khan, W.
Din, N.
Chand, R.
Powiązania:
https://bibliotekanauki.pl/articles/1489921.pdf
Data publikacji:
2012-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Rm
64.60.-i
Opis:
In an experimental setup, consisting of quasi-two-dimensional square cell, the motion of monodisperse spherical steel balls is studied. The cell is vibrated horizontally to eradicate the compaction of balls due to gravity. By raising the number density of the steel balls, the dilute fluid has been gradually alternated into dense fluid. The temperature of granular media, along the driven and transverse directions, has been found to be anisotropic. Transition from granular gas to the liquid-like fluid has been observed. The radial distribution function of the balls in the cell is investigated for the authentication of the structural changes. Furthermore, the fast Fourier transformation for the 2D system is carried out to confirm these changes.
Źródło:
Acta Physica Polonica A; 2012, 121, 3; 699-702
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:
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:
PIPT from the Beginning to Future
Autorzy:
Cailleau, H.
Luty, T.
Koshihara, S.
Servol, M.
Lorenc, M.
Buron-Le Cointe, M.
Collet, E.
Powiązania:
https://bibliotekanauki.pl/articles/1489952.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
64.70.K-
78.47.D-
Opis:
The birth of the field of photoinduced phase transitions was strongly influenced by the conceptual viewpoint expressed by Professor Y. Toyozawa on the condensation of relaxed excitons. Since this first period, twenty years ago, this young field has been expanding rapidly along a diversity of directions. Nowadays, it goes hand in hand with the challenges of today's science: emergence, nonlinearity, coherence, far away from equilibrium, for example. The control of the functionality of a material via photoexcited states poses many new fundamental questions. Some of them will be overviewed: (i) the nature of the control parameters and the nature of the relevant collective variables, especially the order parameters, which characterize the evolution of the system, (ii) the difference between photoinduced transformations under continuous light irradiation and those resulting from an ultrashort laser pulse, (iii) the physical mechanisms of ultrafast photoinduced phase transitions from the formation and proliferation of phototransformed entities to the softening of a collective mode.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 297-306
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phenomenological Versus Microscopic Interpretation of Incommensurate Systems -BCCD and the ANNNI-Model
Autorzy:
Schaack, G.
Powiązania:
https://bibliotekanauki.pl/articles/1929174.pdf
Data publikacji:
1993-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
64.70.Rh
77.80.Bh
Opis:
Phenomenological and microscopic models to treat modulated crystal structures are reviewed. Their applicability to interpret the specific phase diagram of betaine-calciumchloride-dihydrate (BCCD), which is of the "incomplete devils,s staircase" type, is critically discussed. Some experimental observations, which emphasize the fractal topology of the BCCD phase diagram, have been compiled. They support the preference of microscopic approaches as the ANNNI-model over the classic Landau theory for this specific case.
Źródło:
Acta Physica Polonica A; 1993, 83, 4; 451-462
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rayleigh Scattering of Mössbauer Radiation Method Used in Dynamics Studies of Condensed Matter
Autorzy:
Enescu, S.
Bibicu, I.
Powiązania:
https://bibliotekanauki.pl/articles/2042086.pdf
Data publikacji:
2005-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.45.+x
64.60.-i
64.70.Rh
Opis:
The Rayleigh scatte ring of the Mössbauer radiation is a less common technique used in the study of the properties of condensed matter. The detection of the scattered radiation via the nuclear resonance absorption, with an energy resolution of the order of 10$\text{}^{-8}$ eV makes this technique very sensitive to dynamics changes. The results of our studies by the Rayleigh scattering of the Mössbauer radiation on pyrolytic graphite (C) and rubidium tetrachlorozincate (Rb$\text{}_{2}$ZnCl$\text{}_{4}$) are reported. The contribution of the coherent inelastic scattering to the total intensity in C(002) is presented like a consequence of the coupling motions of C atoms in the hexagonal plane. The normal-incommensurate phase transition in Rb$\text{}_{2}$ZnCl$\text{}_{4}$ is discussed in connection with the photon-phonon interaction.
Źródło:
Acta Physica Polonica A; 2005, 107, 3; 479-489
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Gibbs Measures of the Potts Model with Three Competing Interactions on Cayley Tree of Order 3
Autorzy:
Akin, H.
Saygılı, H.
Powiązania:
https://bibliotekanauki.pl/articles/1186977.pdf
Data publikacji:
2016-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.50.+q
64.60.-i
75.10.Hk
64.60.De
Opis:
In this paper, we consider the Potts model with competing interactions on the Cayley tree of order three. We give the Potts model on the Cayley tree and its recursion relation. We construct the Gibbs states corresponding to the model by using Markov random field method. We calculate the critical curve, such that there is a phase transition for the model. We show that there are phase transition of the model for some given parameters. We extend the results obtained by Akin and Temir (Condensed Matt. Phys. 14, 23003 (2011)).
Źródło:
Acta Physica Polonica A; 2016, 129, 4; 845-848
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Description of Extreme Gibbs Measures for the Ising Model with Three Interactions
Autorzy:
Akin, H.
Ganikhodjaev, N.
Temir, S.
Uguz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1400048.pdf
Data publikacji:
2013-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.50.+q
64.60.-i
64.60.De
75.10.Hk
Opis:
In this paper, we consider an Ising model with three competing interactions (nearest neighbor, next-nearest neighbor, and ternary prolonged neighbor) on the Cayley tree of order two, investigated by Ganikhodjaev et al. We study translation-invariant Gibbs measures of the Ising model with these competing interactions. Also, we investigate the set of the extreme Gibbs measures called Markov random fields with memory 2 of the model.
Źródło:
Acta Physica Polonica A; 2013, 123, 2; 484-487
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of Thin Film with S=1. Isothermal Susceptibility and Magnetic Specific Heat
Autorzy:
Gzik, M.
Balcerzak, T.
Powiązania:
https://bibliotekanauki.pl/articles/1967868.pdf
Data publikacji:
1997-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
75.10.-b
75.70.-i
Opis:
The thermodynamic response functions were studied in thin films in the frame of the Blume-Emery-Griffiths model. The method is based on the analysis of the Gibbs free energy and involves calculations of the magnetization and quadrupolar moment distributions. The temperature dependencies of the susceptibility and specific heat are obtained for various biquadratic interaction parameter and non-zero single-ion anisotropy. The behaviour of these functions in different phases: ferromagnetic, paramagnetic and staggered quadrupolar are illustrated in figures and discussed.
Źródło:
Acta Physica Polonica A; 1997, 92, 3; 543-556
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulations of the 3D Ising Model at Criticality
Autorzy:
Blöte, H. W. J.
Kamieniarz, G.
Powiązania:
https://bibliotekanauki.pl/articles/1930588.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.50.+q
64.60.-i
64.60.Fr
75.40.Mg
64.60.Ak
Opis:
We present some new finite-size results for the Binder cumulant that we obtained by means of a transfer-matrix perturbation expansion and by the cluster Monte Carlo methods - the Swendsen-Wang and Wolff algorithms and the largest-cluster method. A finite-size scaling analysis taking into account a correction to scaling locates the critical coupling at Kc = 0.221649(4).
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 395-398
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Excitonic Instabilities of Deformable Lattice - from Self-Trapping to Phase Transition
Autorzy:
Toyozawa, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1931862.pdf
Data publikacji:
1995-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
71.35.+z
71.38.+i
Opis:
The optically created exciton will be self-trapped if its coupling to phonons is strong enough, and will moreover be self-decomposed if the electron and the hole couple to phonons in an opposite way. The bistability between the parity-conserved and parity-broken self-trapped excitons was observed in alkali halides. The situation is most dramatic if the bistability between the parity-broken self-trapped exciton and the ground state (with no exciton) comes into play since the electron-hole pairs may then be spontaneously generated at every lattice site, resulting in the electronic and structural phase transition. The neutral to ionic phase transition observed in a few organic charge transfer compounds under applied pressure or decreasing temperature can be considered as an example. Recent experiment revealed that TTF-chloranil, among others, is subject to photo-induced transient phase change over hundreds of unit cells per one photon. The dynamics of this process can be described in terms of self-trapping and self-multiplication of a photo-generated charge transfer exciton along the chain through the attractive dipolar interaction. This description of phase transition in terms of exciton dynamics will provide a new paradigm of materiology.
Źródło:
Acta Physica Polonica A; 1995, 87, 1; 47-56
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of Thin Film with S = 1
Autorzy:
Balcerzak, T.
Gzik, M.
Powiązania:
https://bibliotekanauki.pl/articles/1955462.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.-b
64.60.-i
75.70.Ak
Opis:
Blume-Emery-Griffiths model with single-ion anisotropy and biquadratic interactions has been applied for the description of thin magnetic films with S=1. According to the Bogolyubov minimization principle, in the frame of molecular field approximation, the phase diagrams, magnetizations and quadrupolar moments in thin films have been calculated.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 293-296
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:
Chemical Potential Derivative as Hallmark for Phase Transitions
Autorzy:
Pietruszka, M.
Matlak, M.
Powiązania:
https://bibliotekanauki.pl/articles/2011158.pdf
Data publikacji:
1999-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
75.40.Cx
75.50.Ee
Opis:
We study antiferromagnetic properties of the two-band extended s-f model with fluctuating valence in the context of two mutually bound new effects of chemical potential critical behaviour, as well as of critical electron redistribution. In order to exemplify both phenomena we build phase diagrams of the system displaying the dependence of the critical Néel temperatures (T$\text{}_{N}$) of the system versus 4f (5f) level positions. The phase diagram consists of two different areas corresponding to antiferromagnetic and paramagnetic phases. We plot the magnetizations and the correlation functions of the system as functions of temperature. Next, we investigate the temperature dependence of the relative average occupation numbers Δn$\text{}^{f(d)}$ and the chemical potential Δμ for a given 4f (5f) level position E$\text{}_{f}$. Plotting this quantities along the E$\text{}_{f}$ cross-section lines we observe small (of the order of 10$\text{}^{-4}$-10$\text{}^{-3}$) but well localized kinks exactly at the Néel temperature T$\text{}_{N}$. Last but not least, we plot the first derivative of the chemical potential dμ/dT which, as it shows clearly visible jumps at T$\text{}_{N}$, may turn out to be very accurate and sensitive (auxiliary) tool to find critical temperatures of the considered system. Moreover, we plot the difference μ$\text{}_{AF}$-μ$\text{}_{PARA}$ where we subtract a chemical potential value of a reference paramagnetic sample from the actual value of the antiferromagnetic system. Also in this case we report the observation of discontinuous change in slope at T$\text{}_{N}$. Our observations can be extended to point out to a new practical possibility of how to find experimentally the critical temperatures of the antiferromagnetic systems exclusively from the chemical potential measurements. We expect that the same type of measurement, according to our recent and present results, would also apply to all types of critical phenomena in real solids.
Źródło:
Acta Physica Polonica A; 1999, 96, 6; 725-732
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:
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:
Magnetic Phase Transition of Amorphous Alloys FeNiSiB
Autorzy:
Brzózka, K.
Gawroński, M.
Jezuita, K.
Powiązania:
https://bibliotekanauki.pl/articles/1861090.pdf
Data publikacji:
1994-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.-i
75.50.-y
76.80.+y
Opis:
Static and dynamical behaviour of amorphous ferromagnets FeNiSiB was investigated by the Mössbauer spectroscopy and magnetostatic methods below and above T$\text{}_{C}$. The distributions of hyperfine magnetic field in the ferromagnetic phase and quadrupole splitting in the paramagnetic one were extracted by means of the constrained Hesse-Rübartch method. The static critical exponents were determined using the power laws and the Kouvel-Fisher method. The results of the Mössbauer investigations were compared with those obtained by magnetic measurements.
Źródło:
Acta Physica Polonica A; 1994, 85, 1; 195-199
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Critical Behaviour of Some 2D Lattice Models
Autorzy:
Kamieniarz, G.
Blöte, H. W.J.
Dekeyser, R.
Powiązania:
https://bibliotekanauki.pl/articles/1930586.pdf
Data publikacji:
1994-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.50.+q
64.60.-i
64.60.Cn
64.60.Ak
64.60.Fr
75.40.Mg
Opis:
The density series of the non-interacting hard-square lattice gas model are reanalyzed by the ratio, Dlog Padé and differential approximant methods. The problem of poor consistency between series and other results is resolved. Transfer matrix calculations are performed, implementing both finite-size scaling and conformal invariance. Very accurate estimates of the critical exponents y$\text{}_{t}$, and y$\text{}_{h}$ are obtained in agreement with Ising universality. Furthermore, an improvement of the value of the critical density ρ$\text{}_{c}$ is found. In addition, the universal critical-point ratios of the square of the second and the fourth moment of the magnetization for ferromagnetic Ising models on the square and on the triangular lattice with periodic boundary conditions are reported.
Źródło:
Acta Physica Polonica A; 1994, 85, 2; 389-393
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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