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1
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Phase Transition Spin Glass-Long Magnetic Order in New Thiospinels Containing Cu, Cr and Sb

100%
Koroleva L. I., Demin R. V., Mashaev M. K., Saiflullaeva D. A., Virovets T. V., Kessler Y. A., Filimonov D. S.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
441-444
EN
The reentrant spin-glass transition was found in the samples of solid solutions CuCr_{1.5+0.5x}Sb_{0.5-0.5x}S_{4} with x=0.34 and 0.4. The transition temperature to the spin-glass state T_{f}, determined from the bend on the temperature dependence of the initial susceptibility in an ac magnetic field, depends on the measurement frequency. It was shown that the dependence T_{f}(ω) obeys the power law 1/ω=(1/ω_{0})[T_{f}/(T_{f} - T*)]^{zν} assuming existence of the phase transition at T*. The maximum of the temperature dependence of electroresistivity was found for the sample with x=0.34 in T* region. These facts show that considered spin-glass-long magnetic order transition is the phase transition.
2
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On the Possible Analogy between Spin-Glasses and Systems

63%
Łusakowski A.
Acta Physica Polonica A
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1992
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vol. 82
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issue 4
620-622
EN
An analogy between a spin-glass and a material containing DX centers is postulated. The basis of the analogy is the formal identity of the Hamiltonians of these two systems. A correspondence between parameters of the spin-glass and of the DX system is established. Experiments which could support the above idea are proposed.
3
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The Method of Linear Equations for Nonzero Temperatures in One-Dimensional Ising Models

51%
Błaszyk M.
Acta Physica Polonica A
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2005
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vol. 107
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issue 3
451-457
EN
The method of linear equations was applied to nonzero temperatures. Two models were considered. The first is the disordered model of random ferromagnetic and antiferromagnetic integrals whose transition matrix meets the condition of invariance of the sum of terms in each line. Although the other model (one-dimensional Ising model in an external field) is devoid of disorder it does not require any assumptions on the form of the transition matrix.
4
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Exchange Coupling and Exchange Bias in FM/AFM Bilayers for a Fully Compensated AFM Interface

51%
Skubic B., Hellsvik J., Nordström L., Eriksson O.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
25-29
EN
We address the interlayer coupling in a ferromagnet/antiferromagnet bilayer where the interface of the antiferromagnet is fully compensated. We discuss the role of different types of exchange interaction for the interlayer coupling and exchange bias. We propose two types of corrections to the ideal Heisenberg Hamiltonian which may explain exchange bias. The first is a correction for the angular dependence of the exchange interactions and the second a correction due to magnetostriction and interface imperfections. The first correction contributes to an anisotropy at the interface and favors either parallel or perpendicular coupling across the interface. The second correction contributes to the exchange bias. Our analysis is based on atomic spin dynamics simulations, and our results show that small corrections to the ideal Heisenberg Hamiltonian may have macroscopic consequences in systems with frustrated interatomic interactions.
5
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Kondo Lattice and Magnetic Properties in Strongly Correlated Electron Systems

51%
Coqblin B.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
13-17
EN
We review here the magnetic properties of some strongly correlated electron systems and especially cerium and uranium compounds. The normal Kondo lattice model with a localized S=1/2 spin can account for the Kondo-magnetism competition observed in cerium or ytterbium systems, while the underscreened Kondo lattice model with a localized S=1 spin can well account for the ferromagnetism - Kondo coexistence observed in some uranium compounds such as UTe. Then, we discuss the spin glass-Kondo competition and present the resulting phase diagrams showing spin glass, Kondo and magnetically ordered phases observed in disordered heavy fermion cerium alloys such as CeNi_xCu_{1-x} alloys.
6
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Ising Model on Tangled Chain. I. Free Energy and Entropy

51%
Mejdani R.
Acta Physica Polonica A
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1994
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vol. 85
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issue 6
907-918
EN
In this paper we have considered an Ising model defined on tangled chain, in which more bonds have been added to those of pure Ising chain. To understand their competition, particularly between ferromagnetic and antiferromagnetic bonds, we have studied, using the transfer matrix method, some simple analytical calculations and an iterative algorithm, the behaviour of the free energy and entropy, particularly in the zero-field and zero-temperature limit, for different configurations of the ferromagnetic tangled chain and different types of additional interactions (ferromagnetic or antiferromagnetic). We found that the condition J = -J' between the ferromagnetic interaction J along the chain and the antiferromagnetic interaction J' across the chain is somewhat as a "transition region" condition for this behaviour. Our results indicate also the existence of nonzero entropy at zero temperature.
7
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Ising Model on Tangled Chain. II. Magnetization and Susceptibility

51%
Mejdani R.
Acta Physica Polonica A
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1994
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vol. 85
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issue 6
919-935
EN
In the preceding paper we have considered an Ising model defined on tangled chain to study the behaviour of the free energy and entropy, particularly in the zero-field and zero-temperature limit. In this paper, following the main line and basing on some results of the previous work, we shall study in the "language" of state configurations the behaviour of the magnetization and the susceptibility for different conditions of the model, to understand better the competition between the ferromagnetic bonds along the chain and the antiferromagnetic additional bonds across the chain. Particularly interesting is the behaviour of the susceptibility in the zero-field and zero-temperature limit. Exact solutions for the magnetization and susceptibility, generated by analytical calculations and iterative algorithms, are described. The additional bonds, introduced as a form of perfect disorder, indicate a particular effect on the spin correlation. We found that the condition J = -J' between the ferromagnetic interaction J along the chain and the antiferromagnetic interaction J' across the chain is somewhat as a "transition-region" condition for this behaviour.
8
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Replica-Symmetry Broken Solution of Simple Pseudospin Model of Orientational Glass

51%
Walasek K., Lukierska-Walasek K., Wodawski M.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
407-410
EN
The first stage of the replica-symmetry breaking for a simple quadrupolar glass model using the Parisi ansatz has been performed in a wide range of temperatures including T = 0. It has been obtained that the entropy of the system increases considerably compared to that calculated within the replica symmetric theory.
9
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One-Dimensional Spin Glass

51%
Błaszyk M., Fechner B.
Acta Physica Polonica A
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2006
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vol. 110
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issue 1
11-24
EN
Thermodynamics of one-dimensional finite-ranged Ising model with quenched disorder introduced by random admixture of bonds with second neighbours by means of transfer-matrix method was determined. The influence of frustrations and competition on the internal energy, specific heat, correlations functions, and susceptibility was studied.
10
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Spin Frustration in Some Magnetic Compounds

51%
Szytuła A., Gondek Ł., Penc B., Hernandez-Velasco J.
Acta Physica Polonica A
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2004
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vol. 106
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issue 5
583-591
EN
In the paper the results of the powder neutron diffraction measurements of RAuIn (R = Ce, Tb, Dy, and Er) and ZnFe_2O_4 compounds at low temperatures are presented. For the RAuIn compounds, which crystallize in the hexagonal ZrNiAl-type structure, the rare-earth moments lie in the ab-plane and form a typical triangle non-collinear structure. ZnFe_2O_4 has the normal spinel structure in which the Fe^{3+} ions occupy the B sites, forming the corner-shared tetrahedra of the Fe spins. At low temperatures experimental data indicate the coexistence of the long-range and the short-range magnetic order. The obtained results suggest that the important factor which influences the magnetic ordering in these compounds is geometrical frustration of magnetic moments.
11
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A Neural Network Model of an Ising Spin Glass

51%
Wilson K., Goossens D.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
983-986
EN
The behaviour of an Ising spin glass (S=1/2) with infinite range interactions is modelled using a numerical simulation based on a neural network. Thermodynamic variables are defined on the network, and are found to obey the Thouless-Anderson-Palmer theory when the applied magnetic field is zero. When a magnetic field is applied along the spin direction, complex field-dependent behaviour appears, including a state in which the Edwards-Anderson order parameter is independent of temperature below the critical temperature.
12
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Magnetisation and Entropy of a One-Dimensional±J Ising Model in a Uniform Magnetic Field

51%
Błaszyk M.
Acta Physica Polonica A
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2007
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vol. 111
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issue 2
191-200
EN
An approximation scheme related to the averaging procedure over finite fragments of the lattice was proposed. The magnetisation and entropy were calculated numerically. The correctness of this approximation scheme was analysed against the magnetic field and temperature.
13
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The Ground State of Ising Model±J on the Tube

51%
Błaszyk M.
Acta Physica Polonica A
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2003
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vol. 104
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issue 1
3-24
EN
A method of linear equations is proposed allowing a reduction of a physical problem of determination of energy, entropy, or magnetisation for the systems with frozen disorder to a mathematical problem of solving a set of linear equations. Apart from an exact method for determination of energy and entropy, a type of the mean field approach is presented, which permits a summation over series representing entropy. Moreover, it was established that magnetisation can appear only when the antiferromagnetic integrals occur at the zero probability.
14
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Kondo Lattice Models for Rare-Earth and Actinide Systems

51%
Coqblin B.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1005-1013
EN
We present here some works on the strong competition between the Kondo effect, magnetic order and eventually spin glass or frustration effect in anomalous rare-earth and actinide systems. First, we develop an underscreened Kondo lattice model with S_{f} = 1 spins for the 5f-electrons and we have recently improved it by deriving, by the Schrieffer-Wolff transformation, a 5f-band with a finite bandwidth. The underscreened Kondo lattice model can account for properties of some uranium and neptunium compounds, like UTe, Np_2PdGa_3 or UCu_2Si_2 which have a large Curie temperature T_{c} of order 100 K and present also a Kondo behavior. In particular, we can account for the observed maximum of T_{c} under pressure in UTe and the magnetization curves of NpNiSi_2 showing the occurrence of the Kondo effect at low temperatures below T_{c}. Second, we have studied the properties of disordered cerium alloys like CeCu_xNi_{1-x} or CeRh_xPd_{1-x} by considering the Kondo effect, a ferromagnetic order and a spin glass behavior described by several approaches. The van Hemmen approach gives a good explanation of the properties of cerium alloys and we are describing the magnetic glass clusters which occur in both spin glass and ferromagnetic phases. Third, we present a new description of a frustrated Kondo lattice model, which can account for the behavior under pressure or doping of some ytterbium compounds like Yb_2Pd_2Sn and YbAgGe.
15
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Comparison of Properties of One-Dimensional ± J Ising Models on Square Lattices

51%
Błaszyk M.
Acta Physica Polonica A
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2009
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vol. 115
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issue 5
849-853
EN
The energies and entropies of the one-dimensional ± J Ising models on square lattices have been compared. The method proposed in this paper explains the impossibility of getting exact results in nonzero temperatures and specifies the conditions of error minimisation.
16
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A Monte Carlo Study of Critical Properties of Strongly Diluted Magnetic Semiconductor (Ga,Mn)As

51%
Tomczak P., Diep H., Jabłoński P., Puszkarski H.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
514-516
EN
Within a Monte Carlo technique we examine critical properties of diluted bulk magnetic semiconductor (Ga,Mn)As modeled by a strongly diluted ferromagnetic Heisenberg spin-5/2 system on a face centered cubic lattice. We assumed that 5% of Ga atoms is substituted by Mn atoms and the interaction between them is of the RKKY-type. The considered system is randomly quenched and a double average was performed: firstly, over the Boltzmann probability distribution and secondly - over 2048 configurations related to the quenched disorder. We estimated the critical temperature: T_{c}=97±6 K, which is in agreement with the experiment.
17
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Spin Glass State in S=3/2 Kagomé Antiferromagnet Co(N_{3})_{2}(bpg)[(CH_{3})_{2}(NCOH)]_{4/3}

51%
Vrábel P., Čižmár E., Orendáčová A., Gao S., Orendáč M.
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vol. 126
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issue 1
266-267
EN
Specific heat, magnetic susceptibility and magnetization of Co(N_{3})_{2}(bpg)[(CH_{3})_{2}(NCOH)]_{4/3}, representing S=3/2 kagomé system are reported. Long-range ordering at 16 K was revealed, however, at lower temperatures slow spin dynamics is still found. The analysis of alternating susceptibility suggests the onset of glassy state. The study of the time dependence of magnetization revealed the existence of more relaxation channels with pronounced different relaxation times. The observed behaviour is consistent with the formation of topological spin glass in which relaxation is governed by both spin and chiral degrees of freedom.
18
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Spin Glass-Like Transition in Orthorhombic T-Phase Al-Pd(Fe)-Mn Complex Metallic Alloys

51%
Slanovec J., Jagličic Z., Jagodić M., Heggen M., Feuerbacher M., Balanetskyy S., Dolinšek J.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
19-22
EN
Magnetic properties of orthorhombic T-phase Al-Pd(Fe)-Mn - members of complex metallic alloys - with different Pd(Fe)/Mn atomic ratios were studied experimentally. The measured zero field cooling-field cooling splitting, the frequency dependent AC susceptibility and slow thermoremanent magnetization time decay indicate that the samples possess built-in frustration-like properties similar to those in spin glasses.
19
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Application of the SPin Glass Formalism to the Quadrupolar Glass Na(CN)_{x}Cl_{1-x}

51%
Walasek K.
|
EN
A new model of quadrupolar glass of mixed alkali halide-cyanide crystals is proposed. This model is treated by the Sherrington-Kirkpatrick like procedure. Physical consequences of our approach are discussed. The temperature dependence of the quadrupolar Edwards-Anderson order parameter and elastic constant C_{44} near the quadrupolar glass transition was obtained.
20
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One-Dimensional Time-Dependent Frustrated and Disordered Ising Model

51%
Błaszyk M.
Acta Physica Polonica A
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2008
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vol. 114
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issue 4
657-666
EN
The dynamics being modifications of the Glauber one were proposed. The time course of the single spin and two-spin correlation function was determined. These calculations were performed for ordered systems, although a possibility of their extension over disordered ones was indicated.
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