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3 TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

3 2011

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The Electronic Properties of New Fe-Based Superconductors

Kruchinin S., Antonchenko V., Zolotovsky A.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

2011

Vol. 15, No 2

203-208

We investigate the band structure of Fe-based superconductors using the first-principle method of density-functional theory. We calculated the band structure and the density of states at the Fermi level for ReFeAsO (Re = Sm, Dy, Ho, Er) superconductors. Our calculations indicate that the maximum critical superconducting transition temperature Tc will be observed for compounds with Sm and Er. We predict that Tc=60K for ErFeAsO.

Preparation, Magnetic Studies and Band Structure Calculation of NiFe2O4 Nanoparticles

Nabiyouni G., Fesharaki M., Zolotovsky A.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

2011

Vol. 15, No 1

107-119

We have undertaken a comprehensive theoretical study of the band structure, density of states, dependence of the Curie point and saturation magnetization on the size of NiFe2O4 nanoparticles prepared by the conventional ceramic method. Commercially available NiFe2O4 powder was first annealed in an oxygen environment in a furnace at 1100oC for 3h. The X-ray diffraction pattern indicated that the sample was single-phase at this stage. The average grain size estimated by scanning electron microscopy (SEM) was in the range of 300 to 350nm. The magnetic behavior of the sample at room temperature was studied by means of a superconducting quantum interference device (SQUID). The Curie temperature of the nickel ferrite powder was measured using an LCR meter. The measurement of the Curie temperature and saturation magnetization indicated that a decrease in the grain size leads to a decrease in the Curie temperature and in the saturation magnetization. The small value of saturation magnetization was attributed to a spin-glass-like surface layer on the nanocrystalline nickel ferrite with a ferrimagnetically aligned core (H.Nathani and S.Gubbala 2004 J.Mater. Sci. and Engin. B 111 95). Good agreement was obtained between theory and experimental results.

Band Structure of Ruthenate Superconductors

Dow J., Zolotovsky A.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

2011

Vol. 15, No 1

99-105

We investigate the band structure of ruthenates using the first-principles method of density functional theory (DFT). We calculated the band structure and density of states at the Fermi level for superconductors Ba2YRuO6 and Sr2YRuO6. Our calculations show that the maximum critical superconducting transition temperature Tc=93K can be obtained for Ba2YRuO6.