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5 Acta Physica Polonica A

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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.

nr 3

373-376

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.

Preparation and Some Properties of Carbon Nanotubes

88%

Byszewski P. , Ukalski K. , Baran M. , Dlużewski P. , Kozłowski M.

Acta Physica Polonica A

1995

tom 87

nr 4-5

885-891

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.

Optical Response of La_{1-x}MnO_3/Al_2O_3 Films

75%

Babonas G. , Reza A. , Szymczak R. , Baran M. , Fröhlich K. , Jasutis V. , Diduszko R.

nr 1

77-83

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.

Effect of Chemical Disorder on Geometrically Frustrated Kagome Lattice

75%

Szymczak H. , Szymczak R. , Baran M. , Fink-Finowicki J. , Krzymanska B. , Aleshkevych P. , Jezierski A.

nr 1

35-42

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.

Surface Magnetic Anisotropy of Epitaxial La_{0.7}Mn_{1.3}O_{2.84} Thin Films

63%

Aleshkevych P. , Baran M. , Dyakonov V. , Szymczak R. , Szymczak H. , Baberschke K. , Lindner J. , Lenz K.

tom 110

nr 1

57-70

A spin-wave resonance technique was used to collect information on elementary magnon excitations in high quality epitaxial La_{0.7}Mn_{1.3}O_{2.84} films prepared by dc-magnetron sputtering. It was found that besides bulk spin-wave modes, the spin-wave resonance spectrum includes also the surface spin waves. The value of spin-wave stiffness constant D=156 meV·Å^2 was found. The values of the surface magnetic anisotropy on both surfaces and their angular dependence were determined. The experimentally found spin-wave resonance spectra were explained based on the surface-inhomogeneity model. The effect of surface anisotropy on the spin-wave excitation conditions in epitaxial La_{0.7}Mn_{1.3}O_{2.84} films was investigated. Spin-wave resonance data give an indirect evidence of periodic charge-ordered stripes formation.