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Full Susceptibility Tensor for Localized Spin Models with S = 1, 3/2, 2, 5/2 and with Rhombic Anisotropy

100%
Pełka R.
Acta Physica Polonica A
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2011
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vol. 119
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issue 3
428-436
EN
A general discussion of the simulation procedure of the full susceptibility tensor and isothermal magnetization pseudovector for compounds comprising weakly-interacting magnetic centers is presented. A single-crystal-sample as well as a powder-sample case are considered. The procedure is used to obtain explicit expressions for the full susceptibility tensor for spins S = 1, 3/2, 2, and 5/2 for non-vanishing rhombic local anisotropy and any form of spectroscopic tensor.
2
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Hysteresis Effect in Mean-Field Model

100%
Pełka R.
|
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vol. 126
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issue 1
28-29
EN
A simple feedback loop and a mean-field approximation are employed to simulate the memory effect in the exchange-coupled magnetic system. The nonlinearity of the feedback turns out to be the crucial factor for the appearance of hysteresis loops. A threshold value above which the hysteresis disappears is the mean-field transition temperature. Temperature dependence of the coercive field is investigated.
3
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Approximate Approach to Magnetic and Thermodynamic Properties of Mixed Spin (1/2-S) Chains with AB and AB_2 Topology

63%
Pełka R., Pinkowicz D.
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issue 5
959-961
EN
Motivated by the rapid development in the synthesis of novel molecule-based magnets, we have investigated magnetic and thermodynamic properties of mixed spin (s-S) exchange coupled chains displaying a simple linear AB or a knotted AB_2 arrangement. Approximate approach for s = 1/2 and S ≥ 5/2, treating at an intermediate step spin S operator as a commuting variable and using the transfer matrix technique, is used. Susceptibility, magnetization and heat capacity of both spin systems are evaluated numerically from the corresponding free energy for S = 5/2. Uniform ferromagnetic and antiferromagnetic couplings are discussed. The procedure reproduces the right values of saturation magnetization and the entropy content of the systems, corroborating its correctness. χ T curves are shown to depend crucially on the μ_{B} H/J ratio. For zero-field heat capacity a double-peak structure is revealed for the AB chain, whereas for the AB_2 chain only one broad anomaly is observed.
4
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Field-Induced Slow Magnetic Relaxation in Mn₉W₆ Cluster-Based Compound

39%
Konieczny P., Pełka R., Chorazy S., Podgajny R., Sieklucka B., Wasiutyński T.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
884-886
EN
Magnetic measurements of a three-dimensional (3D) molecular magnet built of Mn₉[W(CN)₈]₆ clusters have been carried out to study its static and dynamic properties. Measurements of ac susceptibility in the presence of static magnetic field revealed slow magnetic relaxations. It was found that for the 120 Hz wave frequency the optimal static field which maximizes the imaginary component of the ac susceptibility is about 500 Oe.
5
Content available remote

Photo-Induced Relaxation of Magnetization in Molecular Magnet

39%
Zieliński P., Tracz P., Podgajny R., Pełka R., Bałanda M., Wasiutyński T., Sieklucka B.
Acta Physica Polonica A
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2007
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vol. 112
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issue S
S-183-S-188
EN
The experimental study of photo-induced magnetization of hybrid molecular magnet containing cobalt(II) and tungsten(V) magnetic centers bridged by 4,4'-bpy and CN^- is presented. The observed increase in magnetization rate is attributed to the defects due to inter-valence transfer between Co^{II}W^V↔ Co^{III}W^{IV}. The time evolution of magnetization is parameterized by the power law rather than exponential function.
6
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Magnetic Properties of Transition Metal Molybdates

39%
Konieczny P., Pełka R., Grzesiak-Nowak M., Szymańska A., Łasocha W., Wasiutyński T.
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vol. 126
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issue 1
250-251
EN
Two examples of transition metal molybdates were studied with the use of X-ray diffraction and DC magnetometry techniques. First compound, copper dimolybdate trihydrate CuMo_{2}O_{7}·3H_{2}O contains 2D layers. The second one is fibrillar cobalt trimolybdate octahydrate CoMo_{3}O_{10}·8H_{2}O. Both compounds exhibit paramagnetic behaviour at room temperature. However, in the first one copper ions form dimers linked by oxygen bridges, in which exchange interactions between two localized spin states occur. The second compound consists of isolated cobalt ions in the octahedral surroundings, resulting in magnetic properties deviating from the Curie law.
7
Content available remote

Magnetic Systems at Criticality: Different Signatures of Scaling

27%
Pełka R., Konieczny P., Fitta M., Czapla M., Zieliński P., Bałanda M., Wasiutyński T., Miyazaki Y., Inaba A., Pinkowicz D., Sieklucka B.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
977-989
EN
Different aspects of critical behaviour of magnetic materials are presented and discussed. The scaling ideas are shown to arise in the context of purely magnetic properties as well as in that of thermal properties as demonstrated by magnetocaloric effect or combined scaling of excess entropy and order parameter. Two non-standard approaches to scaling phenomena are described. The presented concepts are exemplified by experimental data gathered on four representatives of molecular magnets.
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