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1
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Weak Ferromagnetism of Fe Intercalated Fullerides

100%
Byszewski P., Diduszko R., Baran M.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
297-302
EN
The magnetic properties of C_{60}Fe_{x} resemble spin glass with the freezing onset above 200 K. The unusual magnetization behavior at intermediate temperatures is ascribed to bonds reorganization.
2
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Critical Current Limitations and Irradiation Effects in High-Temperature

100%
Wiśniewski A., Puźniak R., Baran M., Szymczak H.
Acta Physica Polonica A
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1993
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vol. 84
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issue 1
139-164
EN
The discovery of high-temperature superconductors stimulated many groups of researchers to study properties of these materials. From the basic point of view the most important problem is to clarify the mechanism of high-temperature superconductivity. From the practical point of view the most challenging task is to find mechanisms of strong pinning of the vortices, and thereby to obtain materials with high critical current density. The aim of this paper is to discuss problems connected with critical current limitations and to present possibilities which offer irradiation effects with respect to critical current enhancement.
3
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Magnon Excitations in Manganites

100%
Aleshkevych P., Baran M., Szymczak H.
Acta Physica Polonica A
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2004
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vol. 106
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issue 5
593-602
EN
A review of experimental studies of magnon excitations in manganites is presented. Two kinds of techniques: the inelastic neutron scattering (in bulk materials) and the microwave resonance (in thin films) are considered. Experimental studies of spin dynamics by inelastic neutron scattering in metallic ferromagnetic manganites have shown that at low temperature for small wave vectors k → 0 the dispersion relation has a quadratic shape similar to that observed in Heisenberg ferromagnets. However, the above technique although very informative can be used only for sufficiently large samples of bulk materials. A complementary microwave resonance technique allows studying not only bulk properties, but also surface properties. There are two main theoretical approaches used to interpret the spin wave resonance spectra: the volume inhomogeneity and the surface inhomogeneity models. The last one introduced by Puszkarski has allowed for interpretation of the observed surface magnon excitations in thin films.
4
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Comparison of Flux Pinning in Single Crystals and Melt-Textured YBa_{2}Cu_{3}O_{7-x}

100%
Puźniak R., Wiśniewski A., Baran M., Zhou L.
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EN
Flux pinning properties of single crystals and melt-textured samples of YBa_{2}Cu_{3}O_{7-x} were studied for external magnetic field oriented parallel and perpendicular to the CuO_{2} planes (ab-planes). For H ∥ ab vortex behaviour is mainly determined by a very effective intrinsic pinning mechanism. The irreversibility line is located in the region of higher fields and temperatures in comparison with the irreversibility line for H ⊥ ab. In a single crystal for H ⊥ ab, we observed an increase in the critical current density j_{c} with magnetic field - the so-called "fishtail effect" - in a very broad temperature range. For H ∥ ab, this effect is observed only at temperatures close to T_{c}, when the intrinsic pinning is much weaker.
5
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On Magnetization Reversal in Hard Magnetic Sm-Fe-N Permanent Magnets

100%
Pawlik P., Wysłocki J., Baran M.
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EN
The investigations were carried out on Sm-Fe-N permanent magnets produced by reactive diffusion method. The magnets consist of hard magnetic phases: Sm_2Fe_{17}N_{0.86} and SmFe_5 and soft magneticα-Fe phase. From the comparison of experimentally determined angular dependence of coercive field with appropriate theoretical predictions and from the dependence of coercive field on the external magnetic field determined from the minor hysteresis loops, it was stated that magnetization reversal process in Sm-Fe-N magnets is controlled by the nucleation of reversed domains process.
6
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Magnetic Phase Transitions in Intermetallic GdNi_{5-x}Sn_{1+x} and TbNi_{5-x}Sn_{1+x} Compounds

88%
Baran M., Szymczak H., Szymczak R., Romaka L., Skolozdra R.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
295-299
EN
Magnetization measurements were performed for intermetallic compounds GdNi_{5-x}Sn_{1+x} and TbNi_{5-x}Sn_{1+x} in the temperature range from 4.5 K to 280 K and in magnetic field up to 50 kOe. Complex magnetic phase diagram was revealed for both compounds. The results are discussed assuming three-sublattice magnetic structure and partial disordering of the structure.
7
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Preparation and Some Properties of Carbon Nanotubes

88%
Byszewski P., Ukalski K., Baran M., Dlużewski P., Kozłowski M.
Acta Physica Polonica A
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1995
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vol. 87
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issue 4-5
885-891
EN
Carbon nanotubes can be grown in the DC electric arc, they grow cov­ered by a turbostratic graphite. The mechanism of the tubes growth is dis­cussed. The magnetic susceptibility of samples, which contained aligned nan­otubes exhibits anisotropic oscillatory behavior, which is ascribed to spatial quantization of the energy levels.
8
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Ferromagnetic Resonance Studies of La_{0.67}Ca_{0.33}MnO_3 Film under Stress

88%
Kundys B., Dyakonov V., Baran M., Gierłowski P., Szymczak R.
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EN
Ferromagnetic resonance spectra of the La_{0.67}Ca_{0.33}MnO_3 ferromagnetic film deposited onto the x-cut LiNbO_3 substrate were investigated in a wide temperature range. The strain was mechanically introduced into the film using a special holder configuration. This leads to a shift of resonance field with respect to that of the as-grown sample. Analysis of the magnetic resonance shift, induced by a mechanical stress, allowed us to determine the magnetostriction constant λ_{100}. The magnetostriction determined in this way versus saturation magnetization could be well described by the Callen and Callen theory suggesting the domination of the single ion crystal field interaction in the sample being in the ferromagnetic state.
9
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Magnetic and Transport Properties of R_3Cu_3Sb_4 Compounds (R = La, Ce, Pr, Nd, and Sm)

76%
Skolozdra R., Baran M., Horyn A., Szewczyk A., Gorelenko Y., Szymczak H., Szymczak R.
Acta Physica Polonica A
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2002
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vol. 102
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issue 3
429-435
EN
Magnetic susceptibility, electrical resistivity, and thermopower of the series of the R_3Cu_3Sb_4 compounds (R=La-Sm) were measured over the temperature ranges 1.9-300 K (susceptibility and resistivity) and 80-370 K (thermopower). Below 25 K, resistivity of these compounds grows exponentially with decreasing temperature. For some compounds, R = Ce, Sm, a maximum on temperature dependence of resistivity is observed. Ce_3Cu_3Sb_4 compound undergoes a magnetic transition at 12 K.
10
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Physical Properties of (M_2Cu_2O_3)_m(CuO_2)_n (M = Ca, Sr, Bi) Single Crystals with Bi-2212 Phase on their Surface

76%
Babonas G., Leonyuk L., Maltsev V., Szymczak R., Reza A., Baran M., Dapkus L.
Acta Physica Polonica A
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2001
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vol. 100
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issue 4
553-563
EN
The structural, optical, and magnetic properties are studied in the (M_2Cu_2O_3)_m(CuO_2)_n-type single crystals with the surface on which the Bi-2212-type phase was indicated. The physical properties of such samples were interpreted to some extent by the contributions of two phases. When the secondary phases on the surface of the samples were removed by mechanical polishing or etching by Ar^{+}-ion plasma, the physical properties were typical of the (M_2Cu_2O_3)_m(CuO_2)_n-type crystals. The optical method was shown to be effective for indication of secondary Bi-rich phases on the surface of (M_2Cu_2O_3)_m(CuO_2)_n samples.
11
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Ellipsometric Studies of NdMnO_3 Single Crystals

76%
Babonas G., Reza A., Szymczak R., Baran M., Shiryaev S., Fink-Finowicki J., Szymczak H.
Acta Physica Polonica A
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2004
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vol. 105
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issue 1-2
197-208
EN
Ellipsometric studies of NdMnO_3 single crystals of orthorhombic symmetry were carried out in the spectral range 0.5-5.0 eV. Experimental data, which were obtained on the (001)_{pc}-type planes of pseudo-cubic system, were analyzed in the model of biaxial crystal. For the first time, three componentsε_x,ε_y,ε_z of the effective dielectric function for manganites of orthorhombic symmetry were determined. From ellipsometric data, the spectra of optical conductivity and loss function were also calculated and considered. The fine structure of the spectra and optical anisotropy was the basis for discussion of the microscopic origin of the optical transitions responsible for the optical features. The electronic excitations due to dipole-forbidden spin-allowed transitions of the d-d-type in Mn-ions, f-f-type in Nd-ions and charge-transfer 2p(O)-3d(Mn) transitions were taken into account. The data for NdMnO_3 were compared with those obtained for other related undoped and doped single crystals of perovskite-type structure, LaMnO_3, (LaBa)(MnCo)O_3 and (LaCa)CoO_3.
12
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Optical Response of La_{1-x}MnO_3/Al_2O_3 Films

76%
Babonas G., Reza A., Szymczak R., Baran M., Fröhlich K., Jasutis V., Diduszko R.
Acta Physica Polonica A
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2003
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vol. 103
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issue 1
77-83
EN
La_{1-x}MnO_3 films grown by metal organic chemical vapor deposition technique on r-plane cut Al_2O_3 substrates were investigated. The change of the optical response over the La_{1-x}MnO_3/Al_2O_3 sample surface was investigated along with the temperature dependence of magnetization. The mostly pronounced difference in the spectra of dielectric function occurred in the region of the d-d transitions of Mn-ions. The changes in the optical spectra and magnetic properties were correlated to the structural features of thin film.
13
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Anisotropic Magnetic Susceptibility of Neodymium Substituted SrLaAlO_{4} Crystals

76%
Fink-Finowicki J., Puźniak R., Baran M., Jabłoński R., Berkowski M., Pajączkowska A., Szymczak H.
Acta Physica Polonica A
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1994
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vol. 85
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issue 3
633-637
EN
The uniaxial anisotropy of magnetic properties of SrLa_{1-x}Nd_{x}AlO_{4} single crystals (x = 0.01 and 0.05) was found from the measurements of temperature dependencies of magnetic susceptibility. Results of measurements, with magnetic field along a- and c-axis, are compared with the similar data obtained for CaNdAlO_{4} crystal. The successful description of experimental data was done in frames of the crystal field approximation. The anisotropy of magnetic susceptibility appears due to crystal field acting on magnetic neodymium ions in a system without exchange interactions.
14
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Magnetic Phase Transitions in Pure and Cobalt-Doped Geometrically Frustrated Ni_3V_2O_8 Single Crystals

76%
Szymczak H., Baran M., Szymczak R., Barilo S., Bychkov G., Shiryaev S.
Acta Physica Polonica A
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2007
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vol. 111
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issue 1
71-77
EN
The results of magnetic measurements performed on geometrically frustrated Ni_3V_2O_8 and Ni_{3(1-x)}Co_{3x}V_2O_8 single crystals with x=0.03 are presented. It was found that Co doping did not change considerably the magnetic H-T phase diagram. Although no spin-glass effects were observed, nevertheless, a strong effect of 3 at% cobalt doping was evidenced. The main effect of Co-doping concerns the direction of the antiferromagnetic vector, which for Ni_3V_2O_8 appears along the $a$ axis, while for only slightly Co doped crystals - along the $c$ axis. This switching of direction results from distinct changes of the magnetocrystalline anisotropy due to the presence of Co^{2+} ions strongly coupled to the kagome lattice. The disorder introduced by doping has practically no effect on the magnitude of the isotropic exchange interactions. At the same time the doping suppresses the Dzyaloshinskii-Moriya exchange interactions due to the change of direction of the antiferromagnetic vector.
15
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Effect of Chemical Disorder on Geometrically Frustrated Kagome Lattice

76%
Szymczak H., Szymczak R., Baran M., Fink-Finowicki J., Krzymanska B., Aleshkevych P., Jezierski A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 1
35-42
EN
This paper reviews recent progress in the studies of magnetic dilutions on magnetic properties of two frustrated systems: magnetoplumbite-like SrGa_{12-x}Cr_xO_{19} and kagome staircase Co_3V_2O_8 doped with Mg ions. In the first group of compounds magnetic properties are determined by magnetic defects arising due to doping. In the case of kagome staircase compounds magnetic dilution suppresses effects of crystal field acting on magnetic ions. In particular, the dilution decreases magnetocrystalline anisotropy and anisotropy of magnetization.
16
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Magnetic Properties of Spin-Ladders (A_{2}Cu_{2}O_{3})_{m} (CuO_{2})_{n}

76%
Baran M., Szymczak H., Szymczak R., Dyeyev S., Leonyuk L., Babonas G.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
571-574
EN
Magnetization M(T) and M(H) data of single crystals of the S=1/2 quasi-one-dimensional system (A_{2}Cu_{2}O_{3})_{m}(CuO_{2})_{n} with various A-site constituents are compared. The studied orthorhombic, incommensurate crystals are characterized by m/n=5/7,7/10, and 9/13. The role of rare-earth ions located in A-sites is discussed.
17
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Geometrically Frustrated Kagome Lattice with Chemical Disorder

76%
Szymczak R., Baran M., Fink-Finowicki J., Krzymanska B., Aleshkevych P., Szymczak H.
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EN
The effect of nonmagnetic Mg^{2+} and magnetic Co^{2+} doping in Kagome compounds was investigated using DC magnetic susceptibility. The main effect of doping is to change the crystal field parameters. It was shown that Co^{2+} doping increases considerably crystal field parameters in Ni_3V_2O_8 while doping with nonmagnetic Mg^{2+} ions decreases considerably crystal field parameters in Co_3V_2O_8 crystals.
18
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Electrical Transport and Magnetic Properties of La_{2/3}Pb_{1/3}MnO_3 Thin Films

64%
Baran M., Berkowski M., Fink-Finowicki J., Lewandowski S., Szymczak H., Szymczak R., Khartchev S., Medvedev Y.
Acta Physica Polonica A
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2004
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vol. 105
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issue 1-2
115-120
EN
The magnetic and transport properties of epitaxial La_{2/3}Pb_{1/3}CuO_3 thin films deposited on SrLaGaO_4 substrate using dc magnetron sputtering technique are reported. The giant magnetoresistance effect (of about 50% at magnetic field of 1 T) was observed near the Curie temperature. Several mechanisms responsible for temperature dependence of resistivity are discussed. The effect of annealing was studied. It shifted the Curie temperature to the lower value, probably, because of the loss of oxygen.
19
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Formation of Iron-Containing Clusters in Silica of Predetermined Porosity

64%
Šimkiene I., Baran M., Babonas G., Bendorius R., Rėza A., Szymczak R., Aleshkevych P., Šustavičiūtė R., Tamaševičius R.
Acta Physica Polonica A
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2005
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vol. 107
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issue 2
400-407
EN
Iron-containing nanoparticles and clusters were formed in silica with porosity, which was predetermined by different procedures of sol-gel technology and the chemical composition of precursors. Bulk and layer-type samples of different porosity were synthesized and investigated. The morphology, magnetic, and optical properties were studied to characterize the samples and to analyze the formation of Fe-oxides. Experimental results showed that both Fe_2O_3 and Fe_3O_4 were formed in the samples and that their relative amount was dependent on preparation technology.
20
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Magnetic Properties of EuBaCo_2O_{5.5} Single Crystals

64%
Baran M., Barilo S., Bychkov G., Gatalskaya V., Kurochkin L., Shiryaev S., Szymczak R., Szymczak H.
Acta Physica Polonica A
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2004
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vol. 105
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issue 1-2
209-214
EN
The static magnetization of the EuBaCo_2O_{5.5} single crystals was measured from helium to room temperatures for two configurations of the applied field: parallel and perpendicular to the c-axis. The compound is antiferromagnetic from helium temperature to about 210 K. In low temperature region (below 45 K) the antiferromagnetism coexists with a spin-glass-like state. The metamagnetic field-induced phase transition was observed in the antiferromagnetic phase for magnetic field applied perpendicular to the c-axis. The spontaneous phase transition from antiferromagnetic to weak ferromagnetic phase was established to be of the first order. This transition is accompanied by the appearance of the intermediate state. The weak ferromagnetic phase exists up to T_c=240 K.
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