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1
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Complex Magnetic Behaviour of Ho_3Cu_4X_4 Compounds (X = Si and Sn)

100%
Gondek Ł., Szytuła A., Prokhnenko O.
Acta Physica Polonica A
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2008
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vol. 113
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issue 4
1179-1184
EN
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.
2
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Spin Frustration in Some Magnetic Compounds

100%
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.
3
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Magnetic Properties and Electronic Structure of CeTIn (T = Ni, Cu, Pd, Au) Compounds

100%
Szytuła A., Penc B., Gondek Ł.
Acta Physica Polonica A
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2007
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vol. 111
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issue 4
475-486
EN
The electronic structure of the ternary CeTIn (T = Ni, Cu, Pd, Au) compounds was investigated by means of X-ray photoelectron spectroscopy. Our interest was aimed mainly to the valence bands and the Ce3d core levels of investigated compounds. Analysis of the valence bands indicates that they are mainly determined by the Tnd band, whereas a share of the R4f states can be estimated to be about a few percent only. The analysis of the differential valence bands spectra between CeTIn and LaTIn analogues suggests that the Ce4f^1 ground states shift deeper below the Fermi level with an increase in the 4f level occupation factor. The analysis of the Ce3d spectra made on the basis of the Gunnarsson-Schönhammer model indicates the hybridization parameter equal to 148 meV for CeNiIn, 45 meV for CeCuIn, 177 meV for CePdIn, and 123 meV for CeAuIn.
4
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Low-Temperature Specific Heat and Magnetocaloric Effect in RCu_2Ge_2 (R = Dy-Tm) Compounds

100%
Gondek Ł., Kaczorowski D., Pikul A., Szytuła A.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
391-393
EN
The magnetocaloric effect in RCu_2Ge_2 (R = Dy-Tm) was investigated by means of specific heat measurements. The compounds order antiferromagnetically at 6.2 K (DyCu_2Ge_2), 5.6 K (HoCu_2Ge_2), 3.0 K (ErCu_2Ge_2), and 3.9 K (TmCu_2Ge_2), and some of them exhibit additional magnetic transitions in the ordered state. In an external magnetic field the low-temperature specific heat changes significantly, which can be attributed to metamagnetic-like transitions. In this temperature region, the investigated samples show distinctly different magnetocaloric effect.
5

Zastosowanie radiografii oraz tomografii neutronowej w badaniach dla potrzeb energetyki wodorowej.

88%
Figiel H., Gondek Ł., Ziarek M., Selvaraj N. B., Kardjilov N.
Biuletyn Polskiego Stowarzyszenia Wodoru i Ogniw Paliwowych
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2010
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issue 5
35-40
6
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Magnetic Properties of RSn_{2} (R = Tb, Dy) Compounds

88%
Szytuła A., Kaczorowski D., Gondek Ł., Czub J., Nenkov K.
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issue 4
586-589
EN
Polycrystalline samples of TbSn_{2} and DySn_{2} were studied by means of magnetic susceptibility, electrical resistivity and heat capacity measurements. Both compounds have been found to order antiferromagnetically at low temperatures with some extra features in the ordered state due to changes in their magnetic structures. The two stannides exhibit metallic conductivity. The estimated crystal field levels splitting of Tb^{3+} and Dy^{3+} ground multiplets do not exceed 75 K.
7
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Influence of Co Doping on Crystal and Magnetic Properties of Gd_2Cu_2In

76%
Gondek Ł., Szytuła A., Kaczorowski D., Szewczyk A., Gutowska M., Tyvanchuk Y., Kalychak Y.
Acta Physica Polonica A
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2012
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vol. 122
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issue 1
216-219
EN
Physical properties of Gd_2Cu_{2 - x}Co_{x}In (x = 0.1, 0.2, 0.3) samples are investigated. The paper brings results of X-ray diffraction, magnetometric as well as specific heat studies. It was found that only sample with x = 0.1 exhibits desired crystal structure. Other compositions show existence of impurities due to lack of dissolution Co atoms. For Gd_2Cu_{1.9}Co_{0.1}In sample the Curie temperature of 92.5 K was evidenced. Thus, an enhancement of ferromagnetic correlations with comparison to Gd_2Cu_2In sample was evidenced. It was found that Gd_2Cu_{1.9}Co_{0.1}In sample exhibits magnetocaloric effect within broad temperature range.
8
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Magnetic Properties of Hexagonal RTIn Rare-Earth Intermetallics with Frustration

76%
Szytuła A., Baran S., Gondek Ł., Arulraj A., Penc B., Stüsser N.
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issue 4
590-594
EN
Magnetic properties, including magnetic structure, of some RTIn compounds (R = Tb-Er; T = Cu, Ni, Pd, Pt, Au) with the hexagonal ZrNiAl-type crystal structure are reported. Distribution of the rare earth atoms in the basal plane is similar to the kagomé-lattice. Magnetic moments are localized exclusively on the rare earth atoms and form different types of magnetic ordering. Experimental results are analyzed within the Ruderman-Kittel-Kasuya-Yosida and crystal electric field frames. Monte Carlo simulations, including the J_{1} and J_{2} exchange integrals between nearest and next nearest spins and Dzialoshinsky-Moriya interaction, were performed resulting in a number of magnetic phases, some of which are in good agreement with the magnetic ordering determined in the neutron diffraction experiments.
9
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Thermal Fluctuations in YBCO Thin Film on MgO Substrate

76%
Chrobak M., Woch W., Szwachta G., Zalecki R., Gondek Ł., Kołodziejczyk A., Kusiński J.
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EN
The c-axis orientation YBa_2Cu_3O_δ thin film was prepared directly on MgO substrate by the pulse laser deposition. The thickness of the film was 170 nm. The superconducting critical temperature was T_{c50%}=89 K and the width of superconducting transition was Δ T= 1.6 K. Temperature dependence of the critical current of the film was obtained from the temperature dependences of the imaginary part of the AC susceptibility using the Bean model. The critical current density was J_{c}=1.2×10^7 A/cm^{2} at 77 K in the self field. The critical exponents were calculated for several values of the DC applied magnetic field using the temperature dependences of magnetoresistivity. The thermal fluctuations in vicinity of the critical temperature were analysed.
10
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Influence of the Grain Size on the Magnetic Properties of TbMnO_{3}

52%
Bażela W., Dul M., Dyakonov V., Gondek Ł., Hoser A., Hoffmann J., Penc B., Szytuła A., Kravchenko Z., Nosalev I., Zarzycki A.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
785-788
EN
The magnetic properties including magnetic structure of poly and nano samples of TbMnO_{3} are determined. All the samples investigated are antiferromagnets. In these samples the Mn ad Tb moments order antiferromagnetically at different temperatures and form modulated magnetic structure described by the propagation vector k=(k_{x},0,0) with different value of k_{x} for the Mn and Tb sublattices. Comparison of the data for poly and nano samples indicates the decrease of the moment and increase of the k_{x} component of propagation vector in the nano specimens. The wide Bragg peak related to the Tb sublattice suggests that the magnetic order has the claster-like character. The magnetic moments value in both sublattices is smaller, whereas the k_{x} values are larger for nano samples.
11
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Magnetic and Neutron Diffraction Studies of the Polycrystalline and Nanoparticle TbMnO_3

52%
Bażela W., Dul M., Dyakonov V., Gondek Ł., Hoser A., Hoffmann J., Penc B., Szytuła A., Kravchenko Z., Nosalev I., Zarzycki A.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
384-390
EN
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.
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