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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:
Thermoelectric Power of the $URu_{1-x}Pd_{x}Ge$ System
Autorzy:
Gralak, D.
Toliński, T.
Tran, V.
Powiązania:
https://bibliotekanauki.pl/articles/1385279.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
75.50.Ee
72.15.Jf
Opis:
We report the measurements of thermoelectric power, S(T), of the $URu_{1-x}Pd_{x}Ge$ solid solutions in the temperature range 1.9-300 K. It is found that S(T) of URuGe is consistent with the behaviour of Kondo lattice, characterized by a low-temperature negative minimum and a high-temperature positive maximum. On the contrary, S(T) of the compositions 0.1 ≤ x ≤ 0.7 is negative over the whole temperature range measured and shows only one negative minimum around 200 K. The compositions x = 0.9 and 1, in addition to a high-temperature negative minimum, exhibit anomalies at low temperatures, presumably associated with the magnon drag. We interpret the experimental data assuming the presence of the Kondo and crystal-electric field effects.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 287-289
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermoelectric Power of Single-Crystalline $Ce_{2}RhSi_{3}$
Autorzy:
Szlawska, M.
Kaczorowski, D.
Plackowski, T.
Gulay, L.
Powiązania:
https://bibliotekanauki.pl/articles/1810404.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
75.50.Ee
72.15.Jf
Opis:
High-quality single crystal of $Ce_{2}RhSi_{3}$ was studied by means of thermoelectric power measurements carried out down to 2 K in external magnetic fields up to 13 T. The results obtained above 50 K were interpreted in terms of a modified two-band model that takes into account temperature variation of the width of 4f-derived narrow band located near the Fermi level. At lower temperatures the thermopower exhibits more complex temperature dependences that likely involve interplays of magnetic exchange, Kondo and crystal-field interactions.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 132-134
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamic Properties of Geometrically Frustrated S=1/2 XY Antiferromagnet $Er_{2}Sn_{2}O_{7}$
Autorzy:
Al Ghamdi, N.
Orendáčová, A.
Pavlík, V.
Orendáč, M.
Powiązania:
https://bibliotekanauki.pl/articles/1368676.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Dg
75.50.Ee
75.30.Sg
Opis:
The magnetic susceptibility, specific heat and entropy of geometrically frustrated S=1/2 XY antiferromagnet $Er_{2}Sn_{2}O_{7}$ are reported. It is shown, that temperature dependence of magnetic susceptibility above nominally 10 K is governed by crystal field effects. Systematic study of specific heat in magnetic fields up to 7 T enabled the estimation of exchange coupling, J/k<<4.6 K. Investigation of isothermal change of magnetic entropy upon magnetization from 1 T to 7 T revealed the absence of enhanced magnetocaloric effect. The obtained results suggest that frustration parameter f ≈140 proposed for $Er_{2}Sn_{2}O_{7}$ earlier may be significantly overestimated.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 264-265
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Phase Diagram of the Second-Type Antiferromagnet
Autorzy:
Balcerzak, T.
Radomska, A.
Powiązania:
https://bibliotekanauki.pl/articles/2013394.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.-b
75.50.Ee
75.50.Pp
Opis:
We investigate theoretically the phase diagrams of the second-type antiferromagnet with the fcc structure. Besides the nearest-neighbour and next-nearest-neighbour exchange interactions, the biquadratic and long-range dipolar terms are taken into account. The results can be useful to discuss the phase diagram of europium telluride under external pressure.
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 775-778
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Origin of EPR Signals in SrCuO$\text{}_{2}$ Ceramics
Autorzy:
Augustyniak-Jabłokow, M. A.
Yablokov, Yu. V.
Ivanova, T. A.
Jacyna-Onyszkiewicz, I.
Shustov, V. A.
Powiązania:
https://bibliotekanauki.pl/articles/2043623.pdf
Data publikacji:
2005-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Ee
76.30.Fc
81.05.Je
Opis:
The origin and thermal evolution of the EPR signals in SrCuO$\text{}_{2}$ ceramics are studied. It has been shown that the EPR signals observed in this ceramic material are due to contamination with other phases. The axial signal is due to SrCu(OH)$\text{}_{4}$·H$\text{}_{2}$O, which is a product of water reactions with SrCuO$\text{}_{2}$.
Źródło:
Acta Physica Polonica A; 2005, 108, 2; 345-351
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Mössbauer Spectroscopy and Analytical Investigations οf the Polycrystalline Compounds with General Formula $Zn_xSn_yCr_zSe_4$
Autorzy:
Jendrzejewska, I.
Hanc, A.
Zajdel, P.
Kita, A.
Goryczka, T.
Maciążek, E.
Mrzigod, J.
Powiązania:
https://bibliotekanauki.pl/articles/1811602.pdf
Data publikacji:
2008-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.05.cp
61.66.Fn
75.50.Ee
82.80.Ej
Opis:
We present combined X-ray powder diffraction and Mössbauer $\text{}^{119}Sn$ studies of polycrystalline compounds with a general formula $Zn_xSn_yCr_zSe_4$ (where x+y+z ≈3). The obtained single-phase compounds crystallize in the spinel cubic structure - Fd3m. Tin ions are found to occupy both tetrahedral and octahedral sublattices. On the contrary to the strong tetrahedral site preference energy of Sn, the presented data strongly suggest that the increase in lattice parameters with Sn doping is caused by Sn ions that incorporated into octahedral positions. A quadrupole and isomer shifts of $\text{}^{119}Sn$ in $(SnSe_4)^{6-}$ and $(SnSe_6)^{4-}$ are also reported.
Źródło:
Acta Physica Polonica A; 2008, 114, 6; 1591-1597
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Magnetic Properties of $GaFeO_3$ by Neutron Diffraction and Mössbauer Spectroscopy
Autorzy:
Rećko, K.
Szymański, K.
Dobrzyński, L.
Waliszewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1419611.pdf
Data publikacji:
2012-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.05.fm
61.05.Qr
75.50.Gg
75.50.Ee
75.85.+t
Opis:
The multiferroic $GaFeO_3$ synthesized by a sol-gel method and conventional solid state reaction show remarkably different magnetic transition temperatures. Both samples have orthorhombic crystal structure $Pc2_1n$. Results of a new analysis of neutron diffraction and Mössbauer data are presented. Full agreement between parameters was achieved using the Mössbauer data as the constraints in the refinement of neutron diffraction data at low and at high temperature. Magnetic moments are reported.
Źródło:
Acta Physica Polonica A; 2012, 122, 2; 396-399
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Impact of d- and p-Electron Elements on Magnetic Properties of $RT_{x}X₂$ Compounds
Autorzy:
Gil, A.
Powiązania:
https://bibliotekanauki.pl/articles/1397026.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Eh
75.47.Np
75.50.Ee
75.70.Cn
Opis:
Studies of rare earth compounds with transition metals are one of the dominant trends in modern magnetism and cover a wide range of research both basic and applicative nature. The main aim of the study of lanthanide compounds is to find answers to questions concerning mechanisms of interaction between the magnetic moments. A systematic study of the magnetic properties of rare-earth compounds gives hope for full understanding of magnetism in these families of compounds. For many years the $RT_{x}X₂$ compounds with the crystal structure of CeNiSi₂ - type are in the circle of my interests. Based on my own research and the results published in the literature by other authors, the impact of d- and p-electron elements on magnetic properties of the $RT_{x}X₂$ compounds, where x ≤1 and R = Tb, Dy, Ho, Er; T = Ni, Co, Cu, Fe, Mn, Cr; X = Si, Ge, Sn will be analysed.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 473-476
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Ground-State of the Quantum Spin-1/2 Heisenberg Antiferromagnet on Square-Kagomé Lattice: Resonating Valence Bond Description
Autorzy:
Tomczak, P.
Molińska, A.
Richter, J.
Schulenburg, J
Powiązania:
https://bibliotekanauki.pl/articles/2046847.pdf
Data publikacji:
2006-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Jm
75.45.+j
75.50.Ee
Opis:
In this paper we report on some ground-state properties of the spin-1/2 Heisenberg antiferromagnet on the two-dimensional square-kagomé lattice. Finite N-spin systems were investigated with the use of the resonating valence bond method. Like in the case of spin system on kagomé lattice we find the almost flat dependence of mean singlet length on 1/N.
Źródło:
Acta Physica Polonica A; 2006, 109, 6; 781-787
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Electronic Structure of the RMn$\text{}_{2}$Ge$\text{}_{2}$ (R = Ca, Y, La, Ba) Antiferromagnets
Autorzy:
Toboła, J.
Malaman, B.
Venturini, G.
Powiązania:
https://bibliotekanauki.pl/articles/2013367.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.15.Mb
71.15.Nc
75.20.En
75.20.Hr
75.50.Ee
Opis:
The electronic structure of the tetragonal RMn$\text{}_{2}$Ge$\text{}_{2}$ (R = Ca, Y, La, Ba) antiferromagnets is presented using the self-consistent Korringa-Kohn-Rostoker method. According to the neutron refinements, two types of collinear antiferromagnetic structure are taken into account: AF$\text{}_{1}$ for YMn$\text{}_{2}$Ge$\text{}_{2}$ and AF$\text{}_{2}$ for the other compounds. The calculated magnetic moments on Mn: 2.17μ$\text{}_{B}$ (YMn$\text{}_{2}$Ge$\text{}_{2}$), 2.84 μ$\text{}_{B}$ (CaMn$\text{}_{2}$Ge$\text{}_{2}$), 2.95 μ$\text{}_{B}$ (LaMn$\text{}_{2}$Ge$\text{}_{2}$), and 3.47 μ$\text{}_{B}$ (BaMn$\text{}_{2}$Ge$\text{}_{2}$) remain in good agreement with the neutron data (in μ$\text{}_{B}$) 2.20, 2.67, 3.05, and 3.66, respectively. As seen on antiferromagnetic density of states, all systems are metallic, however BaMn$\text{}_{2}$Ge$\text{}_{2}$ is found near semimetallic limit. The total energy Korringa-Kohn-Rostoker computations on CaMn$\text{}_{2}$Ge$\text{}_{2}$, performed in both antiferromagnetic phases, result in preferring of the AF $\text{}_{2}$ structure.zap
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 761-765
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effect of Phase Decomposition on Magnetic Structure of $Cu_{0.4}Mn_{0.3}Ni_{0.3}$ Alloy
Autorzy:
Świderska, K.
Jankowska-Kisielińska, J.
Powiązania:
https://bibliotekanauki.pl/articles/1385743.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.05.F-
64.75.-g
75.40.-s
75.47.Np
75.50.Ee
81.40.Rs
Opis:
The purpose of present investigation was to study the effects of phase decomposition of the $Cu_{0.4}Mn_{0.3}Ni_{0.3}$ alloy on its magnetic ordering. The single-crystal sample was examined by elastic neutron scattering before and after five subsequent annealing runs. The results indicate that in small fraction of the quenched sample volume there are two types of antiferromagnetic order: one of them AF1 of the long range, the other one of the short range. Ageing induces phase decomposition which yields disappearance of AF1 long range order and increase of the volume of new ordered phase. The results of the investigations of the aged sample indicate that regions of new tetragonal phase exhibit antiferromagnetic ordering with magnetic moments of Mn atoms arranged as in the pure compound MnNi but with unequal domain distribution. The intensity of magnetic component of super-structure reflections increases with the duration of ageing at lower rate than component due to atomic order.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 394-396
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature Dependence of Magnetic Inelastic Neutron Scattering in Mn(12%Ge) Alloy
Autorzy:
Jankowska-Kisielińska, J.
Mikke, K.
Milczarek, J. J.
Hennion, B.
Udovenko, V. A.
Powiązania:
https://bibliotekanauki.pl/articles/1956523.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Ds
75.50.Ee
Opis:
A systematic study of temperature dependence of magnetic inelastic neutron scattering for itinerant antiferromagnet Mn(12%Ge) is presented. At low temperatures the experimental data are well described in terms of damped spin waves. This description becomes insufficient at least 150 K below T$\text{}_{N}$. In the temperature range 200-400 K the integrated intensity of distribution for energy transfer 13 THz increases by one third and the shape of the deconvoluted neutron scattering cross-section changes. These changes suggest that ca. 200 K below T$\text{}_{N}$ an additional contribution to the inelastic neutron scattering starts to appear and that its origin is different from spin waves.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 483-486
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis and Characterization of Magnetoferritin
Autorzy:
Mitróová, Z.
Melníková, L.
Kováč, J.
Timko, M.
Kopčanský, P.
Powiązania:
https://bibliotekanauki.pl/articles/1429123.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Cr
75.50.Ee
75.60.Ej
75.50.Tt
Opis:
The paper presents detailed experimental study of synthesis and characterization a bioinorganic magnetic molecule - magnetoferritin. Magnetoferritin with loading of iron ions per protein molecule in the range from 300 to 3000 was prepared. Size distribution analysis (transmission electron microscopy, dynamic light scattering) shows spherical nanoparticles with particle size distribution from 2 to 12 nm, and hydrodynamic diameter from 12 to 25 nm. The thermomagnetic curves measured after cooling the sample in zero field (zero-field cooling) and under the presence of the measurement field (field cooling) show superparamagnetic behavior with the blocking temperature $T_{b}$ from 22 to 60 K and the magnetization loops measured below $T_{b}$ (at 2 K) show the hysteresis with coercive field from 20 to 30 kA/m depending on the concentration of the magnetic nanoparticles.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1318-1320
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconductivity and Quantum Critical Behavior in Cr_{100-z}Os_z
Autorzy:
Prinsloo, A.
Sheppard, C.
Fernando, P.
Powiązania:
https://bibliotekanauki.pl/articles/1398328.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Ee
75.30.Fv
74.70.Ad
74.40.Kb
Opis:
The magnetic phase diagrams of Cr alloys with group-8 metals, such as Re and Ru, show interesting properties. These include quantum critical and superconducting behavior. In order to extend these investigations this paper reports on the physical properties and the magnetic phase diagram of the $Cr_{100-z}Os_{z}$ system, investigated in a concentration range of 2 ≤ z ≤ 30.6. Structural analysis indicate that samples with z<22 have a bcc structure, while those with z>22 include a cubic A15-type structure. Transport and magnetic property measurements indicate that the antiferromagnetic phase disappears at z ≈ 14 and that samples with concentrations z ≥ 12.2 show superconducting behavior. The magnetic phase diagram of $Cr_{100-z}Os_{z}$ is constructed from the Néel and superconducting transition temperatures obtained from various measurements. The commensurate spin-density-wave to paramagnetic phase line decreases sharply for z>4. Fitting parameters of a power law fit to the commensurate spin-density-wave to paramagnetic phase line indicate possible quantum critical behavior. Present results suggest that this phase line terminates in a superconducting dome near a magnetic quantum critical point, similar to that observed in certain heavy fermion systems, but not previously reported for other Cr alloys.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1132-1134
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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