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Wyświetlanie 1-15 z 15
Tytuł:
New S=1/2 Alternating Chain Compound - High Pressure Form of (VO)$\text{}_{2}$P$\text{}_{2}$O$\text{}_{7^{-}}$
Autorzy:
Azuma, M.
Saito, T.
Hiroi, Z.
Takano, M.
Narumi, Y.
Kindo, K.
Powiązania:
https://bibliotekanauki.pl/articles/2012882.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Jm
75.40.Cx
75.50.Ee
Opis:
The high-pressure phase of (VO)$\text{}_{2}$P$\text{}_{2}$O$\text{}_{7}$ comprises a unique kind of spin-1/2 Heisenberg alternating antiferromagnetic chain, in contrast with the ambient pressure phase containing two crystallographically different chains. Magnetic susceptibility and high-field magnetization data showed the presence of a single spin gap of 23 (magnetization) ~27 (susceptibility) K, not double as observed for the ambient pressure phase. This result shows that the two kinds of chains of the ambient pressure phase have single, different spin gaps.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 205-208
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Towards Spin-Wave Like Approach to the J-J Heisenberg Antiferromagnet in Terms of Composite Spins
Autorzy:
Grzybowski, P.
Chhajlany, R.
Powiązania:
https://bibliotekanauki.pl/articles/1810417.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Jm
75.50.Ee
75.40.Cx
Opis:
Conventional spin-wave approach relies on an expansion around a relevant classical (unentangled) ground state or equivalently the ground state in the mean field approximation for the quantum model. However, for systems which may admit valence bond ground states, such as the staggered J-J' Heisenberg antiferromagnet, single site mean field approximation is obviously an incorrect zeroth order approximation. In this paper, we introduce a mean field approximation for clusters consisting of two spins connected by a strong bond in the aforementioned model. We identify the quantum critical point and calculate the ground state magnetization within this cluster mean field approximation in one and two dimensions. Finally, we derive an effective dimer Hamiltonian, in the standard basis operator formalism, which may be a basis for further spin-wave like expansions around the cluster mean field approximation ground state.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 168-170
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic properties of the RbNd(WO₄)₂ single crystal
Autorzy:
Borowiec, M.
Zubov, E.
Zajarniuk, T.
Barański, M.
Powiązania:
https://bibliotekanauki.pl/articles/1075349.pdf
Data publikacji:
2016-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
75.50.Ee
75.10.-b
Opis:
The magnetic investigations as a function of the temperature and magnetic field for the rubidium neodymium double tungstate RbNd(WO₄)₂ single crystal have been performed. The magnetization was measured in the temperature range from 4.2 to 100 K and for the magnetic field up to 1.5 T. The crystal field and exchange parameters were found.
Źródło:
Acta Physica Polonica A; 2016, 129, 3; 359-361
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Complex Magnetic Behaviour of $Ho_3Cu_4X_4$ Compounds (X = Si and Sn)
Autorzy:
Gondek, Ł.
Szytuła, A.
Prokhnenko, O.
Powiązania:
https://bibliotekanauki.pl/articles/1813174.pdf
Data publikacji:
2008-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.25.+z
75.50.Ee
75.40.Cx
Opis:
Ternary $Ho_3Cu_4X_4$ compounds exhibit very complex magnetic phase diagrams. The rare earth ions occupy two non-equivalent crystal positions. Within both magnetic sublattices, magnetic moments exhibit different magnetic ordering temperatures. Moreover, in light of our results, it seems that both sublattices are weakly coupled between each other. This may be observed as independent changes of propagation vectors etc. The major difference of ordering temperatures between both compounds is likely related to substantial change of interatomic distances. Consequently, completely different crystalline electric field effects are observed.
Źródło:
Acta Physica Polonica A; 2008, 113, 4; 1179-1184
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:
Magnetic Study of Phases in FeVO₄-Co₃V₂O₈ System
Autorzy:
Guskos, N.
Zolnierkiewicz, G.
Pilarska, M.
Typek, J.
Blonska-Tabero, A.
Aidinis, C.
Powiązania:
https://bibliotekanauki.pl/articles/1030217.pdf
Data publikacji:
2017-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
75.50.Ee
76.30.Fc
Opis:
Magnetic properties of four nFeVO₄/(1-n)Co₃V₂O₈ samples obtained in reactions between FeVO₄ and Co₃V₂O₈ (n = 0.96, 0.86, 0.84 and 0.83, samples designated S1, S3, S4, S5, respectively) have been investigated by DC magnetisation in field cooling and zero-field-cooling modes and EPR. DC magnetic susceptibility showed paramagnetic behavior of all samples in high-temperature range (T > 20 K) and transition to antiferromagnetic state at 16-18 K (depending on sample iron content). Additional magnetic freezing at 8 K was registered for S3-S5 samples containing larger amount of cobalt. The Curie-Weiss law in 100-300 K temperature range indicates that Co²⁺ is in the high-spin state (S = 3/2). From the parameters of the hysteresis loop observed for the samples it was calculated that 0.58% of all magnetic (Fe³⁺, Co²⁺) ions were involved in the ferromagnetic states. EPR spectra of the samples were recorded in high temperature range (T > 90 K). The temperature dependence of the spectral parameters (resonance field, linewidth, integrated intensity) suggested the Fe³⁺ high-spin ions coupled by antiferromagnetic interaction and clusters of ions play major role in EPR spectra.
Źródło:
Acta Physica Polonica A; 2017, 132, 1; 24-30
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Studies of S=1 Heisenberg Planar Antiferromagnetic Chain Ni(C$\text{}_{11}$H$\text{}_{10}$N$\text{}_{2}$O)$\text{}_{2}$Ni(CN)$\text{}_{4}$
Autorzy:
Čizmár, E.
Černák, J.
Orendáč, M.
Herrmannsdörfer, T.
Feher, A.
Powiązania:
https://bibliotekanauki.pl/articles/2013230.pdf
Data publikacji:
2000-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
71.20.Be
75.50.Ee
Opis:
In this paper we discuss the results of experimental studies of specific heat and magnetic susceptibility of chain compound Ni(C$\text{}_{11}$H$\text{}_{10}$N$\text{}_{2}$O)$\text{}_{2}$Ni(CN)$\text{}_{4}$. We have observed a Schottky type anomaly at T=2.2 K in a temperature dependence of specific heat and the compound was identified as a S=1 Heisenberg antiferromagnetic chain with the subcritical exchange coupling D/k$\text{}_{B}$=5 K, D/|J|=5.2 and the strong in-plane anisotropy E/k$\text{}_{B}$=2.8 K. It has been found that the in-plane anisotropy affects the region of validity of a diluted exciton model [1] and a strong coupling model [2] for S=1 Heisenberg chains with the strong planar anisotropy. The analysis suggests that the in-plane anisotropy should be considered in any attempt to find a compound potentially located in the boundary of Haldane and "large-D" phases.
Źródło:
Acta Physica Polonica A; 2000, 97, 3; 579-582
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental study of magneto-structural correlations in low-dimensional quantum magnets Cu(en)Cl₂ and Cu(tn)Cl₂
Autorzy:
Tarasenko, R.
Lederová, L.
Orendáčová, A.
Orendáč, M.
Feher, A.
Powiązania:
https://bibliotekanauki.pl/articles/1048202.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.-m
75.50.Ee
75.40.-s
75.40.Cx
Opis:
The present work is focused on the investigation of magneto-structural correlations in Cu(en)Cl₂ and Cu(tn)Cl₂. A comparative study of powder susceptibility and magnetization of both compounds revealed that the replacement of tn by en ligand did not affect single-ion properties. On the other hand, the structure modification led to significant reduction of magnetic interactions as well as lowering the crystal symmetry. The impact of the high pressure on magnetic properties of the compounds is discussed.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 420-422
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic and Neutron Diffraction Studies of the Polycrystalline and Nanoparticle $TbMnO_3$
Autorzy:
Bażela, W.
Dul, M.
Dyakonov, V.
Gondek, Ł.
Hoser, A.
Hoffmann, J.
Penc, B.
Szytuła, A.
Kravchenko, Z.
Nosalev, I.
Zarzycki, A.
Powiązania:
https://bibliotekanauki.pl/articles/1419577.pdf
Data publikacji:
2012-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
75.47.Lx
75.25.-j
75.50.Ee
Opis:
This paper reports on investigations of magnetic properties, crystal and magnetic structures on $TbMnO_3$ prepared in various ways, namely, as conventional polycrystalline sample and two nano particle specimens (synthesized with a sol-gel method at temperatures of 800 and 850°C). The X-ray and neutron diffraction data confirm the orthorhombic crystal structure (space group Pbnm, No. 62) without noticeable differences of the lattice parameters for poly- and nanocompounds. For the polycrystalline sample, a subsequent ordering of the Mn and Tb sublattices with decreasing temperature was observed. Namely, the Mn sublattice exhibits a modulated magnetic structure with the propagation vector k = (0, $k_{x},$ 0) in between 41-5 K. Below T = 21 K, a change from a collinear ($A_{y}$ mode) into non-collinear ($A_{y}G_{z}$ mode) structure was evidenced. Further decreasing of temperature below 10 K results in magnetic ordering of the Tb sublattice (modulated $G_{x}A_{y}F_{z}$ mode). For nanoparticle compounds, magnetic ordering in the Mn and Tb sublattices is described by propagation vector k = (0, $k_{y},$ 0), with $k_{y}$ components higher than observed for polycrystalline sample. The magnetic ordering in the Mn sublattice is described by a collinear $A_{y}$ mode down to 1.6 K where the Tb moment becomes ordered ($G_{x}A_{y}$ mode). The observed broadening of the Bragg peaks connected to the Tb sublattice suggests the cluster-like character of its magnetic structure.
Źródło:
Acta Physica Polonica A; 2012, 122, 2; 384-390
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exchange Interactions in a Low-Dimensional Magnetic System $Cu(H_{2}O)_{2}(en)SO_{4}$
Autorzy:
Sýkora, R.
Legut, D.
Wdowik, U.
Powiązania:
https://bibliotekanauki.pl/articles/1366514.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Hk
75.10.-b
75.40.Cx
75.50.Ee
Opis:
We report a theoretical ab-initio investigation of the exchange interaction between Cu atoms in $Cu(H_{2}O)_{2}(en)SO_{4}$, en=$C_{2}H_{8}N_{2}$(ethylenediamine), an insulating magnetic material. Unlike previous experimental studies which describe the system as a quasi-two-dimensional antiferromagnet, our results, based on the mapping of the system onto an effective Heisenberg model, suggest a quasi-one-dimensional character of magnetism, with the exchange coupling between the Cu atoms being propagated along a zigzag line, lying in the crystal's bc plane and connecting the Cu atoms through the N atoms. Furthermore, we report the calculated positions of the H atoms that have not been provided in experimental papers.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 50-51
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Pressure on the Magnetic Response of the Low-Dimensional Quantum Magnet Cu(H₂O)₂(C₂H₈N₂)SO₄
Autorzy:
Peprah, M.
VanGennep, D.
Blasiola, B.
Quintero, P.
Tarasenko, R.
Xia, J.
Hamlin, J.
Meisel, M.
Orendáčová, A.
Powiązania:
https://bibliotekanauki.pl/articles/1030267.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
75.50.Ee
74.62.Fj
07.35.+k
Opis:
The influence of pressure on the low-dimensional molecular magnet Cu(H₂O)₂(en)SO₄ (en = ethylenediamine = C₂H₈N₂) has theoretically been shown to affect the exchange interactions of the material. Herein, the results of an experimental study of hydrostatic pressure effects on the temperature dependence of the magnetization are reported. Using two different pressure cells, the magnetization measurements were performed between 2 K and 9.6 K with pressures ranging from ambient to 5.0 GPa. The data preliminarily suggest the presence of a shift in the magnetization peak of the material at the lowest temperatures and at the highest applied pressures. These data serve as a guide for future experimental work employing pressure to study this intriguing system.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 901-903
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnet with Ferromagnetic Nearest-Neighbor and Antiferromagnetic Next-Nearest-Neighbor Exchange Interactions
Autorzy:
Szymczak, R.
Szymczak, H.
Kamieniarz, G.
Szukowski, G.
Jaśniewicz-Pacer, K.
Florek, W.
Maltsev, V.
Babonas, G.
Powiązania:
https://bibliotekanauki.pl/articles/1808031.pdf
Data publikacji:
2009-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.40.Cx
75.50.Ee
75.30.Gw
75.30.Et
75.30.Kz
Opis:
Magnetic properties of $Pb[Cu(SO_4)(OH)_2]$ (linarite) natural single crystals were studied by magnetization and specific heat measurements. The angular dependences of magnetization were revealed which correlated with the regularities of the crystal structure. At about 2.8 K this quasi-one-dimensional Heisenberg system undergoes a phase transition to the long-range antiferromagnetic order with antiparallel magnetic moments aligned probably along the b-axis. The antiferromagnetic order is evidenced by the metamagnetic transition and pronounced λ-type anomaly at $T_N$ in the specific heat. Using phenomenological modeling based on a quantum transfer-matrix method, we argue that at higher temperatures linarite is a quasi-one-dimensional system with competing ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor exchange interactions.
Źródło:
Acta Physica Polonica A; 2009, 115, 5; 925-930
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetization Process and Adiabatic Demagnetization of the Antiferromagnetic Spin-1/2 Heisenberg Cubic Cluster
Autorzy:
Strečka, J.
Čisárová, J.
Powiązania:
https://bibliotekanauki.pl/articles/1366469.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Jm
75.30.Sg
75.40.Cx
75.50.Ee
75.60.Ej
Opis:
A full energy spectrum of the spin-1/2 Heisenberg cubic cluster is used to investigate a low-temperature magnetization process and adiabatic demagnetization of this zero-dimensional 2×2×2 quantum spin system. It is shown that the antiferromagnetic spin-1/2 Heisenberg cube exhibits at low enough temperatures a stepwise magnetization curve with four intermediate plateaux at zero, one quarter, one half, and three quarters of the saturation magnetization. We have also found the enhanced magnetocaloric effect close to level-crossing fields that determine transitions between the intermediate plateaux.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 26-27
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Properties of Anion-Radical Salts Based on TCNQ Anion Radical
Autorzy:
Radváková, A.
Kajňaková, M.
Feher, A.
Ziolkovskiy, D.
Starodub, V.
Powiązania:
https://bibliotekanauki.pl/articles/1813852.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Ee
75.30.Et
75.40.Cx
71.70.Gm
72.80.Le
Opis:
We report the experimental results of anion-radical salts based on TCNQ anion radical. DC magnetic susceptibility measurements in the temperature range from 2 K to 300 K and magnetization measurements were performed on two samples: (N-Me-2, 5-di-Me-Pz)$(TCNQ)_2$ and (N-Me-2, 6-di-Me-Pz)$(TCNQ)_2$ using a Quantum Design MPMS.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 499-502
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic and Related Properties of Ternary TmTX Intermetallics
Autorzy:
Kaczorowski, D.
Szytuła, A.
Powiązania:
https://bibliotekanauki.pl/articles/1387896.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.-m
75.30.Cr
75.30.Kz
75.50.Ee
75.47.Np
75.40.Cx
Opis:
We report on the magnetic and thermal properties of a few TmTX compounds, where T = d-electron metal and X = p-electron element. In all these ternaries but TmRuGe the thulium magnetic moments order antiferro- or ferromagnetically at low temperatures. The specific heat data confirms the magnetic orderings and reveals the influence of crystalline electric field effects.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 620-622
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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