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1
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Magnetic Properties of DyTe

100%
Pokrzywnicki S., Duczmal M., Pawlak L., Nenkov K.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
351-354
EN
Dysprosium monotelluride is a metallic substance with one valence electron per formula unit belonging to the conduction band. It crystallizes in the defected NaCl-type structure (a= 0.6070 nm) with cation deficiency in the metal sublattice. AC and DC susceptibilities exhibit a maximum at 15 K and a second maximum at higher temperatures which position is field dependent.
2
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Specific Heat of the Tb_{1-x}La_xNi_2 Solid Solutions

100%
Ćwik J., Palewski T., Nenkov K.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
343-346
EN
Specific heat measurements have been performed on the polycrystalline TbNi_2, LaNi_2 and their solid solutions Tb_{1-x}La_xNi_2 (x=0.2, 0.3). The Debye temperatures, phonon and conduction electron contributions as well as the magnetic part of the heat capacity were determined and discussed. The magnetocaloric effect was estimated from measurements performed in a magnetic field of 0.42 T for TbNi_2, Tb_{0.8}La_{0.2}Ni_2 and Tb_{0.7}La_{0.3}Ni_2.
3
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Composition and Temperature Dependence of Giant Magnetoresistance in Melt-Spun Co_{x}Cu_{100-x} Ribbons

88%
Idzikowski B., Nenkov K., Handstein A., Hütten A., Müller K.-H.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
307-310
EN
Structure, magnetic properties and magnetoresistance in as-quenched and annealed Co_{x}Cu_{100-x} samples were investigated. Homogeneous metastable Co_{x}Cu_{100-x} alloys were prepared by the single-roller technique. The maximum value of magnetoresistance is shifted to higher annealing temperatures with increasing measuring temperature. At higher measuring temperatures the magnetoresistance is not saturated in fields as high as 16 T. Susceptibility measurements showed the formation of hcp-structured Co clusters. For small cobalt concentrations there is a transition from giant magnetoresistance to the normal anisotropic magnetoresistance.
4
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Giant Magnetoresistance in Melt-Spun Co-Cu Modified by Rare Earths

88%
Idzikowski B., Rössler U., Handstein A., Nenkov K., Müller K.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
791-794
EN
Samples of the composition RE_{x}Co_{20}Cu_{80-x}, RE = Sm, Gd or Dy (x = 0, 1, and 3) were produced by melt-spinning and subsequent annealing. The magnetoresistance is negative as in granular Co-Cu, but its values depend on the kind of rare earth element added and on changes in the microstructure induced by thermal annealing. An addition of 1 at.% rare earth metal to Co_{20}Cu_{80} yields a considerable increase in the magnetoresistance ratio, whereas an addition of 3 at.% causes a decrease. E.g., by addition of 1 at.% Dy to Co_{20}Cu_{80} and optimal thermal treatment, the value of magnetoresistance ratio measured at 10 K in a field of 5 T increases from -14% to -28%. The effect can be attributed to the presence of clusters of hexagonal Dy(Co,Cu)_{5}, which was ascertained from X-ray diffraction data, or other, metastable rare-earth compounds and paramagnetic rare-earth atoms in the Cu matrix.
5
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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.
6
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Electron Transport and Point Contact Spectroscopy of Cubic DyCu_{5}

76%
Nenkov K., Idzikowski B., Ilkovic S., Kačmarčiková E., Reiffers M., Müller K.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
843-846
EN
The electron transport properties and point contact spectra of melt-spun DyCu_{5} with the cubic phase (structure type AuBe_{5}, space group $F\overline{4}3m$) were investigated. It was found by ac-susceptibility measurements that below a transition temperature T_{m}=6.5 K this phase shows metamagnetism. Between T_{m} and T_{C}=14.5 K a spontaneous magnetization is found. Our measurements of electrical resistivity confirm the existence of two magnetic phase transitions in the compound. Furthermore, we present point contact spectra of DyCu_{5}-Cu heterocontacts which are directly proportional to the electron-quasiparticle interaction function. Apart from a peak at about 18 meV, which is characteristic of electron-phonon interaction in pure Cu, we observed a series of additional maxima at lower energy, which are connected with the allowed 4f-transitions from the ground state to excited crystalline electric field levels.
7
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Superconducting and Magnetic Phases with 1212-Type of Structure

76%
Khlybov E., Kostyleva I., Nenkov K., Nizhankovskii V., Palewski T., Warchulska J.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
369-372
EN
Studies of magnetic and transport properties of the 1212 compounds MA'_{2}A''Cu_{2}O_{7-x} (M 3D Al or Tl; A'= Sr or Ba; A''= RE, Y, and Ca) revealed a number of interesting magnetic phenomena. Apart from high-temperature superconductivity, these compounds exhibit spontaneous antiferromagnetism, field induced antiferromagnetism or ferromagnetism. The different magnetic orders and superconductivity may be realized in the same compound as a result of the phase separation.
8
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Magnetic Properties and Specific Heat of Laves Phase Tb_{1-x}Sc_{x}Ni_2 (x = 0.1, 0.2) Solid Solutions

76%
Ćwik J., Palewski T., Nenkov K., Lyubina J., Warchulska J., Gutfleisch O., Klamut J.
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issue 5
877-878
EN
Magnetic and specific heat measurements have been performed on polycrystalline TbNi_2, ScNi_2 and their solid solutions Tb_{1-x}Sc_{x}Ni_2 (x = 0.1, 0.2). These compounds were synthesized using high-purity rare-earth metals. It has been found that the magnetic susceptibility of the nonmagnetic ScNi_2 compound exhibits a very weak temperature dependence characteristic of the Pauli paramagnets. TbNi_2, Tb_{0.9}Sc_{0.1}Ni_2 and Tb_{0.8}Sc_{0.2}Ni_2 are typical Curie-Weiss paramagnets and are ferromagnetically ordered below 36 K. As revealed by room-temperature X-ray powder diffraction all the Tb_{1-x}Sc_{x}Ni_2 solid solutions have the cubic Laves C15-type superstructure. The Debye temperature, phonon and conduction electron contributions as well as the magnetic part of heat capacity were determined. The magnetocaloric effect has been studied by means of specific heat measurements in magnetic fields of 0.42 and 1 T. The effect of rare-earth substitution in ScNi_2 on the magnetic and magnetocaloric properties will be discussed.
9
Content available remote

Low-Field Magnetoresistance in Manganite Thin Films

64%
Vlakhov E., Dörr K., Müller K., Handstein A., Nenkov K., Walter T., Chakalov R., Chakalova R., Spasov A.
Acta Physica Polonica A
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2000
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vol. 97
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issue 5
787-790
EN
Grain boundaries play an important role in low-field magnetoresistance of La_{0.7}Ca_{0.3}MnO_{3} and La_{0.7}Sr_{0.3}MnO_{3} thin films deposited by magnetron sputtering and pulsed laser deposition on YSZ(100) and silicon substrates buffered by YSZ. Well-pronounced low-field magnetoresistance hysteresis was observed in magnetic fields applied in in-plane and out-of-plane directions. High values of local magnetoresistance sensitivity d(MR)/dH in the vicinity of the coercive field were obtained reaching up to 0.2%/Oe for La_{0.7}Ca_{0.3}MnO_{3} samples at 5 K.
10
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Structural, Magnetic and Transport Properties οf NdBaCo_{2}O_{5+x} Thin Films Deposited by Magnetron Sputtering

64%
Vlakhov E., Szymczak R., Baran M., Piotrowski K., Szewczyk A., Paszkowicz W., Lobanovskii L., Matyajasik S., Nenkov K., Szymczak H.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
89-91
EN
For the first time, thin films of NdBaCo_{2}O_{5+x} were deposited by RF magnetron sputtering on different substrates. The films deposited on SrLaAlO_4(001) substrates exhibited highly textured structure with c-axis directed out-of-plane. Magnetic measurements M vs. T of three NdBaCo_{2}O_{5+x}/SrLaAlO_4(001) films revealed successively paramagnetic-ferromagnetic-antiferromagnetic transitions with decrease in temperature. Their paramagnetic Curie-Weiss temperatures were estimated to be in the range of T_{C}=100-116 K. Resistivity of the cobaltite thin film exhibited insulating behavior and the best fit was found for the variable range hopping mechanism.
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